EP0643401B1 - Load-related electrical fuse - Google Patents

Load-related electrical fuse Download PDF

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Publication number
EP0643401B1
EP0643401B1 EP94202512A EP94202512A EP0643401B1 EP 0643401 B1 EP0643401 B1 EP 0643401B1 EP 94202512 A EP94202512 A EP 94202512A EP 94202512 A EP94202512 A EP 94202512A EP 0643401 B1 EP0643401 B1 EP 0643401B1
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EP
European Patent Office
Prior art keywords
ceramic
preventive
fuse
tdr
voltage
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Expired - Lifetime
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EP94202512A
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German (de)
French (fr)
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EP0643401A3 (en
EP0643401A2 (en
Inventor
Albert Dr. C/O Philips Patentver.Gmbh Comberg
Rainer Dr. C/O Philips Patentver.Gmbh Waser
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
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Philips Corporate Intellectual Property GmbH
Philips Patentverwaltung GmbH
Koninklijke Philips Electronics NV
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Publication of EP0643401A3 publication Critical patent/EP0643401A3/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/13—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material current responsive
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
    • H01C7/042—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient mainly consisting of inorganic non-metallic substances
    • H01C7/043—Oxides or oxidic compounds
    • H01C7/045—Perovskites, e.g. titanates

Definitions

  • the present invention relates to a load-dependent preventive electrical protection according to the Features of the preamble of claim 1.
  • Fuses are known for electrical circuits. she serve to protect the electrical circuits and devices and machines connected to these if unwanted, usually unpredictable, burdens occur on the circuits that damage them being able to lead. Such loads can cause voltage peaks in the supply network, short circuits due to improper Handling of the devices, too high ambient temperatures or excessive ambient humidity, etc. Corresponding come fuses, thermistors or Humistors alone or in combination with one another Commitment. Such backups are also in the following for short called load securing devices.
  • preventive protection is advantageous, triggering them by a combination or certain Constellation of measured physical quantities is caused. It then becomes logical with each other interconnected preventive safeguards related. Frequently should in addition to the operating time, the accumulated load a machine during its operating life as a decision criterion used for any maintenance intervals become. This is the case with automotive engines, for example Case. It is sufficient to determine the maintenance intervals in usually not to monitor the mileage alone. Rather, it is necessary, as is the accumulated in time Register engine power. Because as a result of Traffic congestion, it is conceivable that the engine will last longer Time is operated with the speedometer cable not rotating.
  • the load on motors is often also direct Relationship to the operating temperature of the motors. That is, each the hotter the engine, the higher its load. Out For this reason, preventive safeguards are of advantage at the same time the operating time as well as the time accumulated operating temperature and thus the temporal accumulated operating load as trigger criterion to use. Such preventive safeguards are described below also load-controlled preventive safeguards called.
  • This problem is addressed in the prior art Preventive protections solved with a combination of corresponding individual sensors for temperature and the time are equipped. Every single one of the individual However, the sensor is also at risk of failure afflicted. Thus the default risk is the compound Preventive protection greater than the default risk each of the individual components. Added to this is the comparison increased assembly effort for a single component.
  • the present invention is based on the object preventive electrical preventive protection create that already as a single component several Can record types of load, is simple and thus minimizing the risk of failure and the assembly effort.
  • the preventive protection according to the invention has an electronic one Ceramic with electrodes inside a case and with lead-out leads for the electrodes.
  • the electronic used Ceramic hereinafter referred to as TDR (Time Dependent Resistor) ceramic called, has a time-dependent according to the invention Resistance, depending on the time of one quasi-insulating state in a semiconducting state ignores what is the trigger criterion.
  • TDR Time Dependent Resistor
  • At the Operation of the preventive protection according to the invention is one DC voltage via the connecting lines to the TDR ceramic and the current increase at the end of the Register operating time and evaluate accordingly.
  • a constant temperature of the device to be monitored according to the invention after a predeterminable number of Operating hours triggering the preventive protection can be achieved.
  • the operating time ⁇ of the TDR ceramic can be controlled in a defined manner both from the temperature T and from the applied DC voltage supply U and the distance d between the electrodes on or in the TDR ceramic.
  • ⁇ A (U / U O ) n1 (D / d O ) n2 exp (E A / KT)
  • the pre-factor A, the exponents n 1 and n 2 , and the activation energy E A are material-dependent constants.
  • U 0 and d 0 denote the voltage or
  • the preventive protection according to the invention is, as from the the aforementioned equation can also be seen from the temperature of the device to be monitored is affected. According to the invention is therefore an extremely simple load-dependent preventive electrical protection specified that both of the operating time and the temperature of a to be monitored device is influenced and quasi automatically a link between the two parameters as a trigger criterion used.
  • PTC element a PTC thermistor
  • any known electronic ceramic the electrical resistance of which exhibits a time-dependent behavior under direct voltage, can be used for the present invention.
  • TDR ceramics are for example from J. Am. Ceram. Soc. 73 (6) 1654-62 (1990) and the literature cited therein.
  • the doped and undoped alkaline earth titanates of the perovskite type such as CaTiO 3 , SrTiO 3 or BaTiO 3 .
  • the alkaline earth ions can be replaced by 0.9-1.1 atm% alkali ions such as sodium ions or potassium ions.
  • Another possibility of doping which can be used alternatively or together with the first possibility, is the doping of the titanium by acceptor ions such as magnesium, aluminum, vanadium, chromium, manganese, iron, nickel or cobalt in an amount of 0.1 to 3 atm%.
  • acceptor ions such as magnesium, aluminum, vanadium, chromium, manganese, iron, nickel or cobalt in an amount of 0.1 to 3 atm%.
  • the TDR ceramic can be made from strontium carbonate, titanium dioxide and nickel hydroxocarbonate, with a composition of SrTi 1.01 Ni 0.001 O 3 .
  • the starting powders were ground beforehand, calcined at 950 to 1100 ° C., ground again, pressed and sintered in oxygen at 1480 ° C. for two hours.
  • the TDR ceramic was then cut into slices up to a few millimeters thick and provided with electrodes on both sides by vapor deposition or baking with a suitable metal paste. Silver, gold, platinum, palladium or other noble metals or alloys between these metals are suitable as metals.
  • this electrodized ceramic disc can be brought into thermal contact with the PTC element either on one side or on both sides.
  • the PTC element can consist of the known PTC ceramics. These are, for example, ceramics made of pure BaTiO 3 or solid solutions of BaTiO 3 with 0 ⁇ atm% PbTiO 3 ⁇ 50 and / or 0 ⁇ atm% SrTiO 3 ⁇ 50.
  • the PTC element can consist of 70 atm% BaTiO 3 and 30 atm % PbTiO 3 exist and thus have a Curie temperature T c of about 260 ° C.
  • Other PTC ceramics based on BaTiO 3 are doped with 0.1 to 0.3 atm% lanthanum, yttrium, bismuth, antimony, tantalum or niobium.
  • the thermal contact can be mediated by a thin Al 2 O 3 or AlN disc or a thin mica plate on which the ceramics are fixed using a temperature-resistant adhesive.
  • the electrodes of the PTC element are also led out of the housing and can either be galvanically isolated with the other leads that are led out, or can be led to the outside with the common ground connection that is then created, while omitting the mica disk.
  • the PTC element is heated to approximately the Curie temperature by an applied DC voltage.
  • the resistance-temperature characteristic of the PTC element leads to a self-stabilization of the temperature in the known manner.
  • the operating time ⁇ of the TDR ceramic now depends on the voltage according to the above equation.
  • the PTC element can e.g. through a metal ash or the like replaced become.
  • the operating time of this preventive protection depends then next to the voltage U and the thickness d of the integral Temperature curve at the contact point of the to be monitored Device.
  • the TDR ceramic made of SrTi 1.01 Ni 0.001 O 3 has to be sintered for six hours at 1340 ° C and then at 1280 ° C hot under 200 bar argon and post-tempered in oxygen at 800 ° C for eight hours.
  • the operating time ⁇ can moreover be varied over a wide range with the aid of the sintering temperature by adding a mol.% Of barium titanate silicate (Ba 2 Si 2 TiO 8 ) to the starting powder after the calcining and painting.
  • barium titanate silicate Ba 2 Si 2 TiO 8
  • the TDR ceramic can also be designed as a multilayer structure with a distance d of the inner electrodes between a few tens to 100 microns, which enables operation with extremely low voltages.
  • the exponent n 2 then has values from 1 to 1.1.
  • Fig. 1 shows a plan view of an inventive preventive electrical protection 10.
  • Preventive protection 10 has a housing 11, which in a TDR ceramic 12 and 12 located inside the housing any existing PTC thermistor 13 completely encloses. Connection lines 14 to the Electrodes 17 of the TDR ceramic 12 or the PTC element 13 lead out of the housing 11. You lead to a voltage source and / or evaluation unit.
  • the Housing 11 can be mounted on a device to be monitored with an attachable pad 15 with a through hole 26 be provided, which at the same time as Extension of the lower end plate of the housing 11 can be executed.
  • the housing 11 can be made of any Material, but preferably be made of copper. This applies in particular to the pad 15.
  • the Housing 11 itself can be cubic or cuboid.
  • the curve profile 18 shown for SrTi 1.01 Ni 0.001 O 3 corresponds approximately to that at a constant temperature of T 260 ° C, corresponds to a voltage U of 80 V and a distance d of 0.5 mm, an insulation resistance 19 of 10 8 ⁇ initially prevailing, which then decreases to a value of approx. 10 5 ⁇ in the region 20 after about two hours.
  • FIG. 3 shows a preventive protection 10 according to the invention on average with a PTC element 13 and one of the also shown TDR ceramic 12 separate ground connection 22. Between the heating PTC element 13 and the TDR ceramic 12 is a mica disk 23 for insulation intended.
  • the connecting lines 14 lead to the respective electrodes 17 of the TDR ceramic 12 and the PTC element 13 and have in Fig. 3 from top to bottom showing a polarization sequence of + - + -.
  • the gap between the housing 11 and the PCT element 13 and the TDR ceramic 12 is filled with glass wool 16.
  • the Bottom of the housing 11 with a not shown in Fig. 3 Be pad 15 and that Housing 11 directly below the TDR ceramic 12 seal and be in thermal contact with it.
  • FIG. 4 shows a preventive protection 10 according to the invention on average with a PTC element 13 and a TDR ceramic 12, which has a common ground connection 24 and thus only three connecting lines 14 leading out have, so that there is a polarization sequence of + - +.
  • the preventive protection 10 according to this FIG. 4 corresponds otherwise of those described in the description of FIG. 3 has been described. In this respect, the description is too Fig. 3 referenced.
  • a preventive protection 10 according to FIG. 3 is made from a acceptor-doped alkaline earth ceramic, e.g. Ni-dope Strontium titanate ceramic as TDR ceramic 12 and one conventional PTC ceramic 13 based on doped Barium titanates or barium / lead titanates or barium / strontium titanates formed that are thermally closely coupled, can also be electrically isolated from one another.
  • a acceptor-doped alkaline earth ceramic e.g. Ni-dope Strontium titanate ceramic as TDR ceramic 12 and one conventional PTC ceramic 13 based on doped Barium titanates or barium / lead titanates or barium / strontium titanates formed that are thermally closely coupled, can also be electrically isolated from one another.
  • the TDR ceramic 13 is produced, for example, from a mixture of strontium carbonate, titanium dioxide and nickel hydroxocarbonate, which leads to a ceramic of the composition SrTi 1.01 Ni 0.001 O 3 .
  • the starting powders were calcined at 950 to 1100 ° C., ground again, pressed and sintered at 1480 ° C. for 2 hours in an oxygen stream.
  • the TDR ceramic 12 was then cut into slices of thickness d (with d between 0.1 and 2 mm).
  • the electrodes 17 were applied on both sides by vapor deposition or by baking in a suitable metal paste. Silver, gold, platinum, palladium or other noble metals or alloys between these metals are suitable as metals.
  • the electrodized ceramic disk was brought into thermal contact with the PTC element 13, which consists, for example, of 70% BaTiO 3 and 30% PbTiO 3 and thus has a Curie temperature T c of approximately 260 ° C., either on one side or on both sides.
  • the thermal contact can by a thin Al 2 O 3 or.
  • AIN disk or mica plate 23 are conveyed, on which the ceramics 12, 13 are fixed by means of a temperature-resistant adhesive 25.
  • the electrical supply lines 14 can either be electrically isolated or, with the mica disc 23 omitted, can be led to the outside with a common ground connection 24.
  • the PTC element 13 is heated to approximately T c by an applied DC voltage.
  • the resistance-temperature characteristic of the PTC element 13 leads to a self-stabilization of the temperature in the known manner.
  • the tripping time that is, the operating time ⁇ of the TDR ceramic 12 depends on the voltage U according to the equation mentioned, the exponent n 1 having a value of approximately -2 for the TDR ceramic 12 listed here.
  • Preventive protection without PTC element 13 for heating is made in the same manner as described above. Instead of the PTC ceramics 13, a connecting tab 15 attached (see Fig. 1), which allows the fuse in close thermal contact with the one to be monitored Bring device.
  • the operating time of this fuse 10 depends on the Voltage U and the thickness d from the integral temperature profile at the contact point of the device to be monitored from.
  • Preventive protection with or without PTC element 13 for Heating can be done in the same way as above described.
  • the sintering condition can be as follows be varied so that the TDR ceramic 12 at 1340 ° C and 6 h is sintered. Then the ceramic 12 at 1280 ° C under 200 bar argon hot pressed and at 800 ° C for Post-annealed in oxygen for 8 hours.
  • the operating time ⁇ of this preventive protection 10 is through a changed microstructure of the ceramic 12 with unchanged Parameters about 1000 times higher.
  • a thickness the ceramic disc 12 of d 0.5 mm
  • a temperature T 200 ° C
  • a voltage of 80 V results in a Operating time ⁇ of preventive protection of 2000 hours.
  • a preventive safety device 10 with or without PTC element 13 can be produced as described above and with changed starting powder according to the previous paragraph.
  • the TDR ceramic 12 is designed as a multilayer structure with a distance d between the internal electrodes of between approximately 15 and 100 ⁇ m. This allows operation with small voltages according to the equation mentioned.
  • the exponent n 2 is approximately 1.0 to 1.1.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Thermistors And Varistors (AREA)
  • Fuses (AREA)

Description

Die vorliegende Erfindung betrifft eine belastungsabhängige elektrische Präventivsicherung entsprechend den Merkmalen des Oberbegriffs des Patentanspruches 1.The present invention relates to a load-dependent preventive electrical protection according to the Features of the preamble of claim 1.

Für elektrische Schaltkreise sind Sicherungen bekannt. Sie dienen dem Schutz der elektrischen Schaltkreise und der mit diesen verbundenen Geräte und Maschinen, wenn unerwünschte, in der Regel nicht vorhergesehene, Belastungen an den Schaltkreisen auftreten, die zu deren Beschädigung führen können. Derartige Belastungen können Spannungsspitzen im Versorgungsnetz, Kurzschlüsse infolge unsachgemäßer Handhabung der Geräte, zu hohe Umgebungstemperaturen oder zu hohe Umgebungsfeuchten, etc. sein. Entsprechend kommen Schmelzsicherungen, Thermistoren oder Humistoren allein oder in Kombination miteinander zum Einsatz. Derartige Sicherungen werden im folgenden auch kurz Belastungssicherungen genannt.Fuses are known for electrical circuits. she serve to protect the electrical circuits and devices and machines connected to these if unwanted, usually unpredictable, burdens occur on the circuits that damage them being able to lead. Such loads can cause voltage peaks in the supply network, short circuits due to improper Handling of the devices, too high ambient temperatures or excessive ambient humidity, etc. Corresponding come fuses, thermistors or Humistors alone or in combination with one another Commitment. Such backups are also in the following for short called load securing devices.

Zur Begrenzung von Überspannungen in elektrischen Schaltkreisen ist beispielsweise aus der EP-B1-0 137 044 ein Varistor bekannt, bei dem die elektrischen Eigenschaften einer halbleitenden Strontiumtitanatkeramik ausgenutzt werden. Elektrische Eigenschaften verschiedener keramischer Kristalle sind beispielsweise aus dem Aufsatz von R. Waser mit dem Titel "dc Electrical Degradation of Perovskite-Type Titanates: II, Single Crystals" bekannt, veröffentlicht im J. Am. Ceram. Soc.73 (6) 1654-62 (1990).To limit overvoltages in electrical circuits is for example from EP-B1-0 137 044 Varistor known for its electrical properties a semiconducting strontium titanate ceramic become. Electrical properties of various ceramic Crystals are from the essay by R. Waser with the title "dc Electrical Degradation of Perovskite-Type Titanates: II, "Single Crystals" known, published in J. Am. Ceram. Soc. 73 (6) 1654-62 (1990).

In manchen Fällen soll es jedoch gar nicht erst zum Ansprechen einer Sicherung kommen. Vielmehr soll das elektrische Gerät mit dem elektrischen Schaltkreis ganz gezielt, nach einer gewissen Betriebs- oder Belastungsdauer, vorsorglich also präventiv abgeschaltet werden. Solche Situationen treten häufig dort auf, wo Maschinen aus Sicherheitsgründen nach bestimmten Belastungsintervallen gewartet werden müssen. Beispiele für derartige Maschinen sind Automobil- oder Flugzeugmotoren. Die Notwendigkeit, ein Gerät vorsorglich abzuschalten, kann aber auch dann gegeben sein, wenn zu vermuten ist, daß das Gerät in naher Zukunft defekt wird und ein Ersatz des Gerätes im noch funktionierenden Zustand einfacher oder kostengünstiger als im defekten Zustand ist. Auch gibt es Geräte, wie z.B. Beleuchtungsquellen, bei denen eine bestimmte Eigenschaft, nämlich deren Helligkeit mit zunehmender Betriebsdauer in einer solchen Weise nachläßt, daß das Gerät auszuwechseln ist, obwohl es bezüglich anderer Eigenschaften, wie dem elektrischen Widerstand durchaus noch funktionsfähig ist. Derartige Sicherungen werden nachfolgend auch kurz Präventivsicherungen genannt.In some cases, however, it should not even be Trip a fuse. Rather, the electrical Device with the whole electrical circuit targeted, after a certain operating or load period, be switched off as a preventative measure. Such situations often occur where machines for safety reasons after certain load intervals need to be serviced. Examples of such Machines are automobile or aircraft engines. The need to switch off a device as a precaution, but can also be given if it can be assumed that the Device becomes defective in the near future and a replacement of the Device in the still working state easier or is cheaper than in the defective state. Also there is Devices such as Illumination sources where one certain property, namely its brightness with decreasing operating time in such a way, that the device should be replaced, even though other properties, such as electrical resistance is still functional. Such fuses are also briefly called preventive safeguards below.

Wichtige Komponenten solcher Präventivsicherungen sind Betriebsstundenzähler, Kilometerzähler oder Durchflußmesser. Im allgemeinen wird ein Zählerstand dazu verwandt, ein optisches oder akustisches Warnsignal auszulösen, so daß eine Abschaltung von Hand oder mittels einer Steuereinheit vorgenommen werden kann. Präventivsicherungen, deren Auslösung ausschließlich von der verstrichenen Zeit abhängt, werden nachfolgend auch kurz zeitabhängige Präventivsicherungen genannt.Important components of such preventive safeguards are Hour meter, odometer or flow meter. In general, a counter reading is used to trigger an optical or acoustic warning signal, so that manual shutdown or by means of a control unit can be made. Preventive fuses, triggering them only from the elapsed time depends, are also briefly time-dependent below Preventive safeguards.

In vielen Fällen sind jedoch Präventivsicherungen vorteilhaft, deren Auslösen durch eine Kombination oder bestimmte Konstellation von gemessenen physikalischen Größen verursacht wird. Es werden dann logisch miteinander verschaltete Präventivsicherungen verwandt. Häufig soll neben der Betriebsdauer auch die akkumulierte Belastung einer Maschine während ihrer Betriebsdauer als Entscheidungskriterium für etwaige Wartungsintervalle herangezogen werden. Dies ist beispielsweise bei Automobilmotoren der Fall. Zur Ermittlung der Wartungsintervalle genügt es in der Regel nicht, den Kilometerstand allein zu überwachen. Vielmehr ist es erforderlich, ebenso die zeitlich akkumulierte Motorleistung zu registrieren. Denn infolge von Vekehrsstaus ist es denkbar, daß der Motor über längere Zeit bei nicht drehender Tachowelle betrieben wird.In many cases, however, preventive protection is advantageous, triggering them by a combination or certain Constellation of measured physical quantities is caused. It then becomes logical with each other interconnected preventive safeguards related. Frequently should in addition to the operating time, the accumulated load a machine during its operating life as a decision criterion used for any maintenance intervals become. This is the case with automotive engines, for example Case. It is sufficient to determine the maintenance intervals in usually not to monitor the mileage alone. Rather, it is necessary, as is the accumulated in time Register engine power. Because as a result of Traffic congestion, it is conceivable that the engine will last longer Time is operated with the speedometer cable not rotating.

Die Belastung von Motoren steht oft auch in direktem Verhältnis zur Betriebstemperatur der Motoren. D.h., je heißer der Motor ist, desto höher ist seine Belastung. Aus diesem Grund sind Präventivsicherungen von Vorteil, die gleichzeitig die Betriebsdauer, wie auch die zeitlich akkumulierte Betriebstemperatur und somit die zeitlich akkumulierte Betriebsbelastung als Auslösekriterium benutzen. Derartige Präventivsicherungen werden nachfolgend auch belastungsgesteuerte Präventivsicherungen genannt. Im Stand der Technik wird dieses Problem durch Präventivsicherungen gelöst, die mit einer Kombination von entsprechenden Individualmeßgebern für die Temperatur und die Zeit ausgerüstet sind. Jeder einzelne der individuellen Meßgeber ist jedoch auch mit einem Ausfallrisiko behaftet. Somit ist das Ausfallrisiko der zusammengesetzten Präventivsicherung größer als das Ausfallrisiko jeder der Einzelkomponenten. Hinzu kommt der im Vergleich zu einer Einzelkomponente erhöhte Montageaufwand.The load on motors is often also direct Relationship to the operating temperature of the motors. That is, each the hotter the engine, the higher its load. Out For this reason, preventive safeguards are of advantage at the same time the operating time as well as the time accumulated operating temperature and thus the temporal accumulated operating load as trigger criterion to use. Such preventive safeguards are described below also load-controlled preventive safeguards called. This problem is addressed in the prior art Preventive protections solved with a combination of corresponding individual sensors for temperature and the time are equipped. Every single one of the individual However, the sensor is also at risk of failure afflicted. Thus the default risk is the compound Preventive protection greater than the default risk each of the individual components. Added to this is the comparison increased assembly effort for a single component.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, eine belastungsabhängige elektrische Präventivsicherung zu schaffen, die bereits als Einzelkomponente mehrere Belastungsarten erfassen kann, einfach aufgebaut ist und somit das Ausfallrisiko und den Montageaufwand minimiert.The present invention is based on the object preventive electrical preventive protection create that already as a single component several Can record types of load, is simple and thus minimizing the risk of failure and the assembly effort.

Erfindungsgemäß wird diese Aufgabe durch die kennzeichnenden Merkmale des Anspruches 1 gelöst.According to the invention, this object is achieved by the characterizing Features of claim 1 solved.

Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen.Further advantageous embodiments of the invention result itself from the subclaims.

Die erfindungsgemäße Präventivsicherung weist eine elektronische Keramik mit Elektroden innerhalb eines Gehäuses und mit herausgeführten Verbindungs- bzw. Anschlußleitungen für die Elektroden auf. Die eingesetzte elektronische Keramik, nachfolgend kurz TDR (Time Dependent Resistor)-Keramik genannt, hat erfindungsgemäß einen zeitabhängigen Widerstand, der in Abhängigkeit von der Zeit von einem quasi isolierenden Zustand in einen halbleitenden Zustand übergeht, was das Auslösekriterium darstellt. Beim Betrieb der erfindungsgemäßen Präventivsicherung ist eine Gleichspannung über die Verbindungsleitungen an die TDR-Keramik anzulegen und der Stromanstieg am Ende der Betriebszeit zu registrieren und entsprechend auszuwerten. Bei konstanter Temperatur des zu überwachenden Geräts kann erfindungsgemäß nach einer vorbestimmbaren Anzahl von Betriebsstunden eine Auslösung der Präventivsicherung erreicht werden.The preventive protection according to the invention has an electronic one Ceramic with electrodes inside a case and with lead-out leads for the electrodes. The electronic used Ceramic, hereinafter referred to as TDR (Time Dependent Resistor) ceramic called, has a time-dependent according to the invention Resistance, depending on the time of one quasi-insulating state in a semiconducting state ignores what is the trigger criterion. At the Operation of the preventive protection according to the invention is one DC voltage via the connecting lines to the TDR ceramic and the current increase at the end of the Register operating time and evaluate accordingly. At a constant temperature of the device to be monitored according to the invention after a predeterminable number of Operating hours triggering the preventive protection can be achieved.

Erfindungsgemäß läßt sich die Betriebszeit τ der TDR-Keramik in definierter Weise sowohl von der Temperatur T, als auch von der angelegten Gleichspannungsversorgung U und dem Abstand d der Elektroden auf oder in der TDR-Keramik steuern. Dabei hat sich überraschend folgende Gesetzmäßigkeit gezeigt: τ = A (U/Uo)n1 (d/do)n2 exp (EA/kT) In dieser Gleichung sind der Vorfaktor A, die Exponenten n1 und n2, sowie die Aktivierungsenergie EA materialabhängige Konstanten. U0 und d0 bezeichnen die Spannungs- bzw. According to the invention, the operating time τ of the TDR ceramic can be controlled in a defined manner both from the temperature T and from the applied DC voltage supply U and the distance d between the electrodes on or in the TDR ceramic. The following legality has surprisingly been shown: τ = A (U / U O ) n1 (D / d O ) n2 exp (E A / KT) In this equation, the pre-factor A, the exponents n 1 and n 2 , and the activation energy E A are material-dependent constants. U 0 and d 0 denote the voltage or

Längeneinheit. Durch Variation der Keramik kann insbesondere der Faktor A um einige Größenordnungen verändert und gezielt eingestellt werden.Unit length. By varying the ceramic, in particular the factor A changed by several orders of magnitude and be set specifically.

Die erfindungsgemäße Präventivsicherung wird, wie aus der vorgenannten Gleichung ersichtlich, auch von der Temperatur des zu überwachenden Geräts beeinflußt. Erfindungsgemäß ist somit also eine äußerst einfache belastungsabhängige elektrische Präventivsicherung angegeben, die sowohl von der Betriebszeit als auch der Temperatur eines zu überwachenden Geräts beeinflußt wird und quasi automatisch eine Verknüpfung beider Meßgrößen als Auslösekriterium verwendet.The preventive protection according to the invention is, as from the the aforementioned equation can also be seen from the temperature of the device to be monitored is affected. According to the invention is therefore an extremely simple load-dependent preventive electrical protection specified that both of the operating time and the temperature of a to be monitored device is influenced and quasi automatically a link between the two parameters as a trigger criterion used.

Es ist jedoch auch denkbar, daß die Temperatur des zu überwachenden Geräts kein geeignetes Auslösekriterium darstellt. Erfindungsgemäß ist dann auf einfache Weise der TDR-Keramik eine Eigenheizung zuzuordnen, die durch einen Kaltleiter, nachfolgend kurz PTC-Element genannt, gebildet sein kann.However, it is also conceivable that the temperature of the monitoring device is not a suitable trigger criterion represents. According to the invention is then in a simple manner To assign TDR ceramics to a self-heating system that is controlled by a PTC thermistor, hereinafter referred to as PTC element can be.

Für die vorliegende Erfindung kann jede bekannte elektronische Keramik, deren elektrischer Widerstand unter Gleichspannung ein zeitabhängiges Verhalten zeigt, verwendet werden. Derartige TDR-Keramiken sind beispielsweise aus J. Am. Ceram. Soc.73 (6) 1654-62 (1990) und der dort zitierten Literatur bekannt. Im Rahmen der vorliegenden Erfindung ist es bevorzugt, die dotierten und undotierten Erdalkalititanate vom Perowskit-Typ, wie CaTiO3 ,SrTiO3 oder BaTiO3 zu verwenden. Dabei können zur Dotierung die Erdalkali-Ionen durch 0,9 -1,1 atm% Alkali-Ionen wie Natriumionen oder Kaliumionen ersetzt werden. Eine andere Möglichkeit der Dotierung, die alternativ oder zusammen mit der ersten Möglichkeit angewendet werden kann, ist die Dotierung des Titans durch Akzeptorionen, wie Magnesium, Aluminium, Vanadin, Chrom, Mangan, Eisen, Nickel oder Kobalt in einer Menge von 0,1 bis 3 atm%.Any known electronic ceramic, the electrical resistance of which exhibits a time-dependent behavior under direct voltage, can be used for the present invention. Such TDR ceramics are for example from J. Am. Ceram. Soc. 73 (6) 1654-62 (1990) and the literature cited therein. In the context of the present invention it is preferred to use the doped and undoped alkaline earth titanates of the perovskite type, such as CaTiO 3 , SrTiO 3 or BaTiO 3 . For doping, the alkaline earth ions can be replaced by 0.9-1.1 atm% alkali ions such as sodium ions or potassium ions. Another possibility of doping, which can be used alternatively or together with the first possibility, is the doping of the titanium by acceptor ions such as magnesium, aluminum, vanadium, chromium, manganese, iron, nickel or cobalt in an amount of 0.1 to 3 atm%.

Beispielsweise kann die TDR-Keramik aus Strontiumcarbonat, Titandioxid und Nickelhydroxocarbonat hergestellt werden, mit einer Zusammensetzung von SrTi1,01Ni0,001O3. Die Ausgangspulver wurden zuvor gemahlen, bei 950 bis 1100°C kalziniert, erneut gemahlen, verpreßt und bei 1480°C für zwei Stunden in Sauerstoff gesintert. Anschließend wurde die TDR-Keramik in Scheiben von bis zu einigen Millimetern Dicke geschnitten und beidseitig durch Aufdampfen oder Einbrennen mit einer geeigneten Metallpaste mit Elektroden versehen. Als Metalle sind Silber, Gold, Platin, Palladium oder andere Edelmetalle bzw. Legierungen zwischen diesen Metallen geeignet. Diese elektrodierte Keramikscheibe kann, um zu einer rein zeitgesteuerten Präventivsicherung zu gelangen, entweder einseitig oder beidseitig in thermischen Kontakt mit dem PTC-Element gebracht werden.For example, the TDR ceramic can be made from strontium carbonate, titanium dioxide and nickel hydroxocarbonate, with a composition of SrTi 1.01 Ni 0.001 O 3 . The starting powders were ground beforehand, calcined at 950 to 1100 ° C., ground again, pressed and sintered in oxygen at 1480 ° C. for two hours. The TDR ceramic was then cut into slices up to a few millimeters thick and provided with electrodes on both sides by vapor deposition or baking with a suitable metal paste. Silver, gold, platinum, palladium or other noble metals or alloys between these metals are suitable as metals. In order to achieve a purely time-controlled preventive protection, this electrodized ceramic disc can be brought into thermal contact with the PTC element either on one side or on both sides.

Das PTC-Element kann aus den bekannten PTC-Keramiken bestehen. Diese sind z.B. Keramiken aus reinem BaTiO3 oder feste Lösungen von BaTiO3 mit 0 < atm% PbTiO3 < 50 und/oder 0< atm%SrTiO3 < 50. Beispielsweise kann das PTC-Element aus 70 atm% BaTiO3 und 30 atm% PbTiO3 bestehen und damit eine Curietemperatur Tc von etwa 260°C haben. Andere PTC-Keramiken auf der Basis von BaTiO3 sind mit 0,1 bis 0,3 atm% Lanthan, Yttrium, Wismut, Antimon, Tantal oder Niob dotiert. Der thermische Kontakt kann durch eine dünne Al2O3 - bzw. AlN-Scheibe oder ein dünnes Glimmerplättchen vermittelt werden, auf dem die Keramiken mittels eines temperaturbeständigen Klebers fixiert werden. Die Elektroden des PTC-Elements sind ebenfalls aus dem Gehäuse herausgeführt und können mit den anderen herausgeführten Leitungen entweder galvanisch getrennt oder unter Weglassen der Glimmerscheibe mit dem dann entstehenden gemeinsamen Masseanschluß nach außen geführt werden. Im Betrieb wird das PTC-Element durch eine angelegte Gleichspannung etwa auf die Curietemperatur aufgeheizt. Die Widerstand-Temperatur-Kennlinie des PTC-Elements führt in der bekannten Weise zu einer Selbststabilisierung der Temperatur. Die Betriebszeit τ der TDR-Keramik hängt nun nach der oben genannten Gleichung von der Spannung ab.The PTC element can consist of the known PTC ceramics. These are, for example, ceramics made of pure BaTiO 3 or solid solutions of BaTiO 3 with 0 <atm% PbTiO 3 <50 and / or 0 <atm% SrTiO 3 <50. For example, the PTC element can consist of 70 atm% BaTiO 3 and 30 atm % PbTiO 3 exist and thus have a Curie temperature T c of about 260 ° C. Other PTC ceramics based on BaTiO 3 are doped with 0.1 to 0.3 atm% lanthanum, yttrium, bismuth, antimony, tantalum or niobium. The thermal contact can be mediated by a thin Al 2 O 3 or AlN disc or a thin mica plate on which the ceramics are fixed using a temperature-resistant adhesive. The electrodes of the PTC element are also led out of the housing and can either be galvanically isolated with the other leads that are led out, or can be led to the outside with the common ground connection that is then created, while omitting the mica disk. In operation, the PTC element is heated to approximately the Curie temperature by an applied DC voltage. The resistance-temperature characteristic of the PTC element leads to a self-stabilization of the temperature in the known manner. The operating time τ of the TDR ceramic now depends on the voltage according to the above equation.

Ohne das PTC-Element liegt, wie bereits erwähnt, die zeitund temperaturabhängige Präventivsicherung vor. Das PTC-Element kann z.B. durch eine Metallasche o.dgl. ersetzt werden. Die Betriebszeit dieser Präventivsicherung hängt dann neben der Spannung U und der Dicke d vom integralen Temperaturverlauf an der Kontaktstelle des zu überwachenden Geräts ab.Without the PTC element, as already mentioned, the time and temperature-dependent preventive protection. The PTC element can e.g. through a metal ash or the like replaced become. The operating time of this preventive protection depends then next to the voltage U and the thickness d of the integral Temperature curve at the contact point of the to be monitored Device.

Um die Betriebszeit der bereits genannten Präventivsicherung mit einem PTC-Element von bislang einigen Stunden auf einige tausend Stunden zu erhöhen, ist die TDR-Keramik aus SrTi1,01Ni0,001O3 bei 1340°C sechs Stunden zu sintern und anschließend bei 1280°C unter 200 bar Argon heiß zu pressen und bei 800°C für acht Stunden in Sauerstoff nachzutempern.In order to increase the operating time of the aforementioned preventive protection with a PTC element from a few hours to a few thousand hours, the TDR ceramic made of SrTi 1.01 Ni 0.001 O 3 has to be sintered for six hours at 1340 ° C and then at 1280 ° C hot under 200 bar argon and post-tempered in oxygen at 800 ° C for eight hours.

Die Betriebszeit τ kann überdies mit Hilfe der Sintertemperatur über einen großen Bereich variiert werden, in dem dem Ausgangspulver nach dem Kalzinieren und Malen ein Mol.% Bariumtitanatsilikat (Ba2Si2TiO8) zugegeben wurde.The operating time τ can moreover be varied over a wide range with the aid of the sintering temperature by adding a mol.% Of barium titanate silicate (Ba 2 Si 2 TiO 8 ) to the starting powder after the calcining and painting.

Die TDR-Keramik kann überdies als Vielschichtstruktur mit einem Abstand d der Innenelektroden zwischen einigen zehn bis 100 µm ausgebildet sein, was den Betrieb mit äußerst kleinen Spannungen ermöglicht. Der Exponent n2 hat dann Werte von 1 bis 1,1. The TDR ceramic can also be designed as a multilayer structure with a distance d of the inner electrodes between a few tens to 100 microns, which enables operation with extremely low voltages. The exponent n 2 then has values from 1 to 1.1.

Ausführungsbeispiele der vorliegenden Erfindung werden nachfolgend unter Bezugnahme auf eine Zeichnung näher erläutert. Darin zeigt:

Fig. 1
die Draufsicht auf eine erfindungsgemäße elektrische Präventivsicherung,
Fig. 2
den qualitativen Verlauf des Isolationswiderstands über der Zeit einer erfindungsgemäßen TDR-Keramik,
Fig. 3
eine erfindungsgemäße Präventivsicherung im Schnitt mit PTC-Element und getrenntem Masseanschluß, und
Fig. 4
eine erfindungsgemäße Präventvsicherung im Schnitt mit PTC-Element und gemeinsamem Masseanschluß.
Exemplary embodiments of the present invention are explained in more detail below with reference to a drawing. It shows:
Fig. 1
the top view of an electrical preventive protection according to the invention,
Fig. 2
the qualitative course of the insulation resistance over time of a TDR ceramic according to the invention,
Fig. 3
a preventive protection according to the invention in section with PTC element and separate ground connection, and
Fig. 4
an inventive prevention on average with PTC element and common ground connection.

Fig. 1 zeigt eine Draufsicht einer erfindungsgemäßen elektrischen Präventivsicherung 10. Die Präventivsicherung 10 weist ein Gehäuse 11 auf, welches eine im Inneren des Gehäuses 11 befindliche TDR-Keramik 12 und einen ggf. vorhandenen PTC-Kaltleiter 13 vollständig umschließt. Verbindungsleitungen 14, die zu den Elektroden 17 der TDR-Keramik 12 bzw. des PTC-Elements 13 führen, sind aus dem Gehäuse 11 herausgeführt. Sie führen zu einer Spannungsquelle und/oder Auswerteinheit. Das Gehäuse 11 kann zur Montage an ein zu überwachendes Gerät mit einer anbaubaren Anschlußfläche 15 mit einer Durchgangsbohrung 26 versehen sein, die gleichzeitig auch als Verlängerung der unteren Abschlußplatte des Gehäuses 11 ausgeführt sein kann. Das Gehäuse 11 kann aus beliebigem Material, vorzugsweise aber aus Kupfer hergestellt sein. Dies betrifft insbesondere die Anschlußfläche 15. Das Gehäuse 11 selbst kann würfel- oder quaderförmig sein. Da die im Inneren befindliche TDR-Keramik 12 und das ggf. vorhandene PTC-Element 13 eine zylindrische Form mit kreisförmiger Grundfläche haben, ist der verbleibende Hohlraum des Gehäuses 11 mit Glaswolle 16 ausgepolstert. Ferner ist in Fig. 1 eine Elektrode 17 der TDR-Keramik 12 zu erkennen.Fig. 1 shows a plan view of an inventive preventive electrical protection 10. Preventive protection 10 has a housing 11, which in a TDR ceramic 12 and 12 located inside the housing any existing PTC thermistor 13 completely encloses. Connection lines 14 to the Electrodes 17 of the TDR ceramic 12 or the PTC element 13 lead out of the housing 11. You lead to a voltage source and / or evaluation unit. The Housing 11 can be mounted on a device to be monitored with an attachable pad 15 with a through hole 26 be provided, which at the same time as Extension of the lower end plate of the housing 11 can be executed. The housing 11 can be made of any Material, but preferably be made of copper. This applies in particular to the pad 15. The Housing 11 itself can be cubic or cuboid. There the inside TDR ceramic 12 and the existing PTC element 13 with a cylindrical shape have a circular base, is the remaining Cavity of the housing 11 padded with glass wool 16. 1 is an electrode 17 of the TDR ceramic 12 to recognize.

Fig. 2 zeigt den qualitativen Verlauf des Isolationswiderstands R über der Zeit t der erfindungsgemäß zum Einsatz kommenden TDR-Keramik 12. Der dargestellte Kurvenverlauf 18 für SrTi1,01Ni0,001O3 entspricht etwa dem, der bei einer konstanten Temperatur von T 260°C, einer Spannung U von 80 V und einem Abstand d von 0,5 mm entspricht, wobei zunächst ein Isolationswiderstand 19 von 108 Ω vorherrscht, der dann nach etwa zwei Stunden auf einen Wert von ca. 105 Ω im Bereich 20 zurückgeht.2 shows the qualitative profile of the insulation resistance R over time t of the TDR ceramic 12 used according to the invention. The curve profile 18 shown for SrTi 1.01 Ni 0.001 O 3 corresponds approximately to that at a constant temperature of T 260 ° C, corresponds to a voltage U of 80 V and a distance d of 0.5 mm, an insulation resistance 19 of 10 8 Ω initially prevailing, which then decreases to a value of approx. 10 5 Ω in the region 20 after about two hours.

Diese Abhängigkeit, daß sich also die Betriebszeit τ in definierter Weise sowohl von der Temperatur, als auch von der angelegten Spannung und dem Abstand d der Elektroden 17 auf oder in der TDR-Keramik steuern läßt, entspricht überraschenderweise dem folgenden und auch schon eingangs genannten empirischen Gesetz: τ = A (U/Uo)n1 (d/do)n2 exp (EA/kT) In dieser Gleichung sind der Vorfaktor A, die Exponenten n1 und n2, sowie die Aktivierungsenergie EA materialabhängige Konstanten. U0 und d0 bezeichnen die Spannungs- bzw. Längeneinheit. Durch die Variation der Keramik kann insbesondere der Faktor A um einige Größenordnungen geändert und gezielt eingestellt werden, wodurch die absteigende Flanke 21 des Kurvenverlaufs 18 in Fig. 2 auf der Zeitskala nach rechts bzw. links verschoben werden kann. This dependency that the operating time τ can be controlled in a defined manner both from the temperature and from the applied voltage and the distance d between the electrodes 17 on or in the TDR ceramic surprisingly corresponds to the following empirical, which has already been mentioned Law: τ = A (U / U O ) n1 (D / d O ) n2 exp (E A / KT) In this equation, the pre-factor A, the exponents n 1 and n 2 , and the activation energy E A are material-dependent constants. U 0 and d 0 denote the unit of tension or length. By varying the ceramic, the factor A in particular can be changed by a few orders of magnitude and set in a targeted manner, as a result of which the descending flank 21 of the curve profile 18 in FIG. 2 can be shifted to the right or left on the time scale.

Fig. 3 zeigt eine erfindungsgemäße Präventivsicherung 10 im Schnitt mit einem PTC-Element 13 und einem von der ebenfalls dargestellten TDR-Keramik 12 getrenntem Massenanschluß 22. Zwischen dem heizenden PTC-Element 13 und der TDR-Keramik 12 ist eine Glimmerscheibe 23 zur Isolation vorgesehen. Die Verbindungsleitungen 14 führen auf die jeweiligen Elektroden 17 der TDR-Keramik 12 und des PTC-Elements 13 und haben in der Fig. 3 von oben nach unten weisend eine Polarisatonsfolge von +-+-. Der Zwischenraum zwischen dem Gehäuse 11 und dem PCT-Element 13 und der TDR-Keramik 12 ist mit Glaswolle 16 ausgefüllt. Anstelle des PTC-Elements 13 kann, wie bereits ausgeführt, der Boden des Gehäuses 11 mit einer in Fig. 3 nicht dargestellten Anschlußfläche 15 versehen sein und das Gehäuse 11 direkt unterhalb der TDR-Keramik 12 verschließen und mit dieser thermisch in Kontakt stehen.3 shows a preventive protection 10 according to the invention on average with a PTC element 13 and one of the also shown TDR ceramic 12 separate ground connection 22. Between the heating PTC element 13 and the TDR ceramic 12 is a mica disk 23 for insulation intended. The connecting lines 14 lead to the respective electrodes 17 of the TDR ceramic 12 and the PTC element 13 and have in Fig. 3 from top to bottom showing a polarization sequence of + - + -. The gap between the housing 11 and the PCT element 13 and the TDR ceramic 12 is filled with glass wool 16. Instead of of the PTC element 13 can, as already stated, the Bottom of the housing 11 with a not shown in Fig. 3 Be pad 15 and that Housing 11 directly below the TDR ceramic 12 seal and be in thermal contact with it.

Fig. 4 zeigt eine erfindungsgemäße Präventivsicherung 10 im Schnitt mit einem PTC-Element 13 und eine TDR-Keramik 12, die eine gemeinsamen Masseanschluß 24 und somit nur drei herausgeführte Verbindungsleitungen 14 haben, so daß sich eine Polarisationsfolge von +-+ ergibt. Die Präventivsicherung 10 gemäß dieser Fig. 4 entspricht ansonsten derjenigen, die in der Beschreibung zu Fig. 3 beschrieben wurde. Insoweit wird auf die Beschreibung zu Fig. 3 verwiesen.4 shows a preventive protection 10 according to the invention on average with a PTC element 13 and a TDR ceramic 12, which has a common ground connection 24 and thus only three connecting lines 14 leading out have, so that there is a polarization sequence of + - +. The preventive protection 10 according to this FIG. 4 corresponds otherwise of those described in the description of FIG. 3 has been described. In this respect, the description is too Fig. 3 referenced.

Hinsichtlich der TDR-Keramik 12 ist noch darauf hinzuweisen, daß diese auch mit mehreren Elektroden 17 schichtweise aufgebaut sein kann.With regard to the TDR ceramic 12, it should also be pointed out that this also with several electrodes 17 in layers can be built.

Hinsichtlich der Herstellung bzw. der Zusammensetzungen der an sich aus dem eingangs genannten Stand der Technik bekannten Keramiken wird folgendes ausgeführt: With regard to the production or the compositions the per se from the prior art mentioned at the outset known ceramics:

Eine Präventivsicherung 10 gemäß Fig. 3 wird aus einer akzeptordotierten Erdalkalititanatkeramik, z.B. Ni-dotieren Strontiumtitanatkeramik als TDR-Keramik 12 und einer herkömmlichen PTC-Keramik 13 auf der Basis von dotierten Bariumtitanaten bzw. Barium/Bleititanaten oder Barium/Strontiumtitanaten gebildet, die thermisch eng gekoppelt, elektrisch auch voneinander isoliert sein können.A preventive protection 10 according to FIG. 3 is made from a acceptor-doped alkaline earth ceramic, e.g. Ni-dope Strontium titanate ceramic as TDR ceramic 12 and one conventional PTC ceramic 13 based on doped Barium titanates or barium / lead titanates or barium / strontium titanates formed that are thermally closely coupled, can also be electrically isolated from one another.

Die TDR-Keramik 13 wird beispielsweise aus einer Mischung aus Strontiumcarbonat, Titandioxid und Nickelhydroxocarbonat hergestellt, welches zu einer Keramik der Zusammensetzung SrTi1,01Ni0,001O3 führt. Die Ausgangspulver wurden gemahlen bei 950 bis 1100°C kalziniert, erneut gemahlen, verpreßt und bei 1480°C für 2 Stunden im Sauerstoffstrom gesintert. Anschließend wurde die TDR-Keramik 12 in Scheiben der Dicke d (mit d zwischen 0,1 und 2 mm) geschnitten. Die Elektroden 17 wurden beidseitig durch Aufdampfen oder durch Einbrennen einer geeigneten Metallpaste aufgebracht. Als Metalle sind Silber, Gold, Platin, Palladium oder andere Edelmetalle bzw. Legierungen zwischen diesen Metallen geeignet. Die elektrodierte Keramikscheibe wurde entweder einseitig oder beidseitig in thermischen Kontakt mit dem PTC-Element 13 gebracht, welches beispielsweise aus 70 % BaTiO3 und 30 % PbTiO3 besteht und damit eine Curietemperatur Tc von etwa 260°C hat. Der thermische Kontakt kann durch eine dünne Al2O3-bzw. AIN-Scheibe oder Glimmerplättchen 23 vermittelt werden, auf denen die Keramiken 12, 13 mittels eines temperaturbeständigen Klebers 25 fixiert werden.The TDR ceramic 13 is produced, for example, from a mixture of strontium carbonate, titanium dioxide and nickel hydroxocarbonate, which leads to a ceramic of the composition SrTi 1.01 Ni 0.001 O 3 . The starting powders were calcined at 950 to 1100 ° C., ground again, pressed and sintered at 1480 ° C. for 2 hours in an oxygen stream. The TDR ceramic 12 was then cut into slices of thickness d (with d between 0.1 and 2 mm). The electrodes 17 were applied on both sides by vapor deposition or by baking in a suitable metal paste. Silver, gold, platinum, palladium or other noble metals or alloys between these metals are suitable as metals. The electrodized ceramic disk was brought into thermal contact with the PTC element 13, which consists, for example, of 70% BaTiO 3 and 30% PbTiO 3 and thus has a Curie temperature T c of approximately 260 ° C., either on one side or on both sides. The thermal contact can by a thin Al 2 O 3 or. AIN disk or mica plate 23 are conveyed, on which the ceramics 12, 13 are fixed by means of a temperature-resistant adhesive 25.

Wie in Fig. 3 und 4 dargestellt, können die elektrischen Zuleitungen 14 entweder galvanisch getrennt oder unter Weglassen der Glimmerscheibe 23 mit gemeinsamem Masseanschluß 24 nach außen geführt werden. Im Betrieb wird das PTC-Element 13 durch eine angelegte Gleichspannung etwa auf Tc aufgeheizt. Die Widerstands-Temperatur-Kennlinie des PTC-Element 13 führt in der bekannten Weise zu einer Selbststabilisierung der Temperatur. Die Auslösezeit, also die Betriebszeit τ der TDR-Keramik 12 hängt nach der genannten Gleichung von der Spannung U ab, wobei der Exponent n1 für die hier aufgeführte TDR-Keramik 12 einen Wert von etwa -2 hat. Fig. 2 zeigt den Widerstand einer Keramikscheibe 12 mit einer Dicke d = 0,5 mm und einer Elektrodenfläche von etwa 200 mm2. Bei der Temperatur T = 260°C wird eine gewünschte Betriebszeit der Präventivsicherung von τ = 2 h bei einer Spannung von 80 V erreicht.As shown in FIGS. 3 and 4, the electrical supply lines 14 can either be electrically isolated or, with the mica disc 23 omitted, can be led to the outside with a common ground connection 24. In operation, the PTC element 13 is heated to approximately T c by an applied DC voltage. The resistance-temperature characteristic of the PTC element 13 leads to a self-stabilization of the temperature in the known manner. The tripping time, that is, the operating time τ of the TDR ceramic 12 depends on the voltage U according to the equation mentioned, the exponent n 1 having a value of approximately -2 for the TDR ceramic 12 listed here. FIG. 2 shows the resistance of a ceramic disc 12 with a thickness d = 0.5 mm and an electrode area of approximately 200 mm 2 . At the temperature T = 260 ° C, a desired preventive fuse operating time of τ = 2 h at a voltage of 80 V is achieved.

Eine Präventivsicherung ohne PTC-Element 13 zum Heizen wird in gleicher Weise hergestellt, wie oben beschrieben. Anstelle der PTC-Keramiken 13 wird eine Anschlußlasche 15 angebracht (siehe Fig. 1), die es erlaubt, die Sicherung in engen, thermischen Kontakt mit dem zu überwachenden Gerät zu bringen.Preventive protection without PTC element 13 for heating is made in the same manner as described above. Instead of the PTC ceramics 13, a connecting tab 15 attached (see Fig. 1), which allows the fuse in close thermal contact with the one to be monitored Bring device.

Die Betriebszeit dieser Sicherung 10 hängt neben der Spannung U und der Dicke d vom integralen Temperaturverlauf an der Kontaktstelle des zu überwachenden Gerätes ab.The operating time of this fuse 10 depends on the Voltage U and the thickness d from the integral temperature profile at the contact point of the device to be monitored from.

Eine Präventivsicherung mit oder ohne PTC-Element 13 zum Heizen kann in gleicher Weise hergestellt sein, wie oben beschrieben. Die Sinterbedingung kann jedoch in der Weise variiert werden, daß die TDR-Keramik 12 bei 1340°C und 6 h gesintert wird. Anschließend wird die Keramik 12 bei 1280°C unter 200 Bar Argon heißgepreßt und bei 800°C für 8 Stunden in Sauerstoff nachgetempert.Preventive protection with or without PTC element 13 for Heating can be done in the same way as above described. However, the sintering condition can be as follows be varied so that the TDR ceramic 12 at 1340 ° C and 6 h is sintered. Then the ceramic 12 at 1280 ° C under 200 bar argon hot pressed and at 800 ° C for Post-annealed in oxygen for 8 hours.

Die Betriebszeit τ dieser Präventivsicherung 10 ist durch eine geänderte Mikrostruktur der Keramik 12 bei unveränderten Parametern etwa 1000-fach höher. Bei einer Dicke der Keramikscheibe 12 von d = 0,5 mm, einer Temperatur T = 200°C und einer Spannung von 80 V ergibt sich eine Betriebszeit τ der Präventivsicherung von 2000 Stunden.The operating time τ of this preventive protection 10 is through a changed microstructure of the ceramic 12 with unchanged Parameters about 1000 times higher. With a thickness the ceramic disc 12 of d = 0.5 mm, a temperature T = 200 ° C and a voltage of 80 V results in a Operating time τ of preventive protection of 2000 hours.

Eine Präventivsicherung 10 mit oder ohne PTC-Element 13 kann wie oben beschrieben hergestellt sein. Dem Ausgangspulver kann nach dem Kalzinieren und Mahlen 1mol% Bariumtitanatsilikat (Ba2Si2TiO8) zugegeben werden. Dies erlaubt die Betriebszeit τ der Sicherung 10 mit Hilfe der Sintertemperatur über einen großen Bereich zu variieren. Bei einer Temperatur von 360°C, einer Spannung 125 V und Scheibendicken von 1 mm ergibt beispielsweise eine Sinterung bei 1340°C für 6 h eine Betriebszeit τ = 140 h, eine Sinterung bei 1380°C für 6 h eine Betriebszeit τ = 28 h und eine Sinterung bei 1460°C für 2 h eine Betriebszeit τ = 11 h.A preventive lock 10 with or without a PTC element 13 can be produced as described above. After calcining and grinding, 1 mol% barium titanate silicate (Ba 2 Si 2 TiO 8 ) can be added to the starting powder. This allows the operating time τ of the fuse 10 to be varied over a wide range using the sintering temperature. At a temperature of 360 ° C, a voltage of 125 V and disc thicknesses of 1 mm, for example, sintering at 1340 ° C for 6 h results in an operating time τ = 140 h, sintering at 1380 ° C for 6 h results in an operating time τ = 28 h and sintering at 1460 ° C for 2 h an operating time τ = 11 h.

Eine Präventivsicherung 10 mit oder ohne PTC-Element 13 kann wie oben beschrieben und bei verändertem Ausgangspulver gemäß vorstehendem Absatz hergestellt werden. Die TDR-Keramik 12 wird dabei als Vielschichtstruktur mit einem Abstand d der Innenelektroden zwischen etwa 15 und 100 µm ausgebilet. Dies erlaubt nach der genannten Gleichung den Betrieb mit kleinen Spannungen. Der Exponent n2 ist etwa 1,0 bis 1,1.A preventive safety device 10 with or without PTC element 13 can be produced as described above and with changed starting powder according to the previous paragraph. The TDR ceramic 12 is designed as a multilayer structure with a distance d between the internal electrodes of between approximately 15 and 100 μm. This allows operation with small voltages according to the equation mentioned. The exponent n 2 is approximately 1.0 to 1.1.

Claims (14)

  1. A load-controlled preventive fuse for monitoring a desired operating time τ, comprising a ceramic resistive body (12) whose electric resistance changes, in dependence upon a period of time and a second type of load, from an initially insulating state with a high resistance value to a semiconducting state with a lower resistance value, while a dc voltage is applied to the resistive body, and comprising electrodes (17) for applying the dc voltage to the resistive body during said period of time, means for measuring the resistance of the ceramic resistive body, and an evaluation unit for monitoring a transition of the resistance value of the resistive body.
  2. A preventive fuse as claimed in Claim 1, characterized in that the operating time τ, i.e. the fulfilment of the activation criterion, is governed by the first and the second type of load of the applied dc voltage U and by the interspace d between electrodes (17) on and/or in the TDR ceramic (12).
  3. A preventive fuse as claimed in Claim 2, characterized in that on the basis of the ceramic material the first type of load causes a dependence on time and the second type of load causes a dependence on temperature, and the connection between the dependence on time and the dependence on temperature can be expressed by the following law: τ = A(U/U0)n1 (d/d0)n2 exp (EA/kT) wherein the factor A, the exponents n1 and n2 as well as the activating energy EA are material-dependent constants, and U0 and d0 are, respectively, the voltage unit and the unit of length.
  4. A preventive fuse as claimed in Claim 3, characterized in that a housing (11) accommodates the TDR ceramic (12) which is provided with electrodes (17) and which is embedded in glass wool (16), the electrical connection leads (14) of the ceramic material being led outwards and at least one of the circular cross-sectional areas, each of which has an electrode (17), being thermally influenceable.
  5. A preventive fuse as claimed in Claim 4, characterized in that the thermal influence is obtained by a suitably arranged end plate having a connection surface (15), via which end plate the preventive fuse (10) is mechanically and thermally connected to the device to be monitored.
  6. A preventive fuse as claimed in Claim 4, characterized in that the housing (11) comprises an intrinsic heating element in the portion of the TDR ceramic (12) which can be thermally influenced, which intrinsic heating element also has outwardly extending connection leads (14) enabling a defined temperature setting.
  7. A preventive fuse as claimed in Claim 6, characterized in that the intrinsic heating element is constituted by a PTC element (13), which is based on doped barium titanates and/or barium/lead titanates and/or barium/strontium titanates, for example 70% BaTiO3 and 30% PbTiO3, and which is thermally closely coupled to one or more than one side of the TDR ceramic (12) and which comprises electrodes (17) on its circular cross-sectional areas.
  8. A preventive fuse as claimed in Claim 7, characterized in that the thermal contact is established by a thin Al2O3 or AlN disc or by a thin mica plate (23) on one side of which there is attached the TDR ceramic (12) and on the other side of which there is attached the PTC element (13) by means of a temperature-resistant adhesive (25).
  9. A preventive fuse as claimed in Claim 8, characterized in that the electrical connection leads (14) of the TDR ceramic (12) and of the PTC element (13) are led out of the housing (11) in an electrically separated manner and in that the PTC element (13) is heated to approximately the Curie temperature Tc by applying a dc voltage.
  10. A preventive fuse as claimed in Claim 8, characterized in that the TDR ceramic (12) and the PTC element (13) are fixed one on top of the other by means of a temperature-resistant adhesive (25) and in that their electrodes form a common ground connection (24) at this area, so that only three connection leads (14) are led out of the housing, and in that the PTC element (13) is heated to the Curie temperature Tc by applying a dc voltage.
  11. A preventive fuse as claimed in any one of the preceding Claims, characterized in that the TDR ceramic (12) is manufactured from a doped or non-doped alkaline earth titanate of the Perovskite type.
  12. A preventive fuse as claimed in Claim 11, characterized in that the TDR ceramic (12) is manufactured from a Ni-doped strontium titanate ceramic of the composition SrTi1,01Ni0,001O3.
  13. A preventive fuse as claimed in Claim 12, characterized in that at a predetermined dc voltage U, an exponent n1 of -2, a thickness d of the TDR ceramic (12) of 0,5 mm and an electrode surface area of 200 mm2 at a temperature T of 260 °C, an operating time τ of 2 hours is obtained at a voltage of 80 V.
  14. A preventive fuse as claimed in Claim 13, characterized in that the TDR ceramic (12) is constructed as a multilayer structure comprising inner electrodes with an interspace d of approximately 15 to 100 °m, as a result of which an exponent n2 of approximately 1.0 to 1.1 is obtained.
EP94202512A 1993-09-09 1994-09-02 Load-related electrical fuse Expired - Lifetime EP0643401B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4330534A DE4330534A1 (en) 1993-09-09 1993-09-09 Load-dependent electrical preventive protection
DE4330534 1993-09-09

Publications (3)

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EP0643401A2 EP0643401A2 (en) 1995-03-15
EP0643401A3 EP0643401A3 (en) 1997-04-02
EP0643401B1 true EP0643401B1 (en) 2002-05-29

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Application Number Title Priority Date Filing Date
EP94202512A Expired - Lifetime EP0643401B1 (en) 1993-09-09 1994-09-02 Load-related electrical fuse

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US (1) US6133819A (en)
EP (1) EP0643401B1 (en)
JP (1) JPH07192599A (en)
DE (2) DE4330534A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7119655B2 (en) * 2004-11-29 2006-10-10 Therm-O-Disc, Incorporated PTC circuit protector having parallel areas of effective resistance
US8154376B2 (en) * 2007-09-17 2012-04-10 Littelfuse, Inc. Fuses with slotted fuse bodies

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2039065A1 (en) * 1970-08-06 1972-02-17 Kind Dieter Prof Dr Ing Process and arrangements for the current-limiting interruption of direct and alternating currents of high voltage
US3931602A (en) * 1970-08-10 1976-01-06 Micro Devices Corporation Thermal limiter for one or more electrical circuits and method of making the same
US3805022A (en) * 1972-10-10 1974-04-16 Texas Instruments Inc Semiconducting threshold heaters
US3878501A (en) * 1974-01-02 1975-04-15 Sprague Electric Co Asymmetrical dual PTCR package for motor start system
US3976854A (en) * 1974-07-31 1976-08-24 Matsushita Electric Industrial Co., Ltd. Constant-temperature heater
US4016521A (en) * 1975-05-23 1977-04-05 Seybold Joseph F Thermal limiter
US4068281A (en) * 1976-09-15 1978-01-10 General Electric Company Thermally responsive metal oxide varistor transient suppression circuit
EP0137044B1 (en) * 1983-02-10 1991-03-27 Matsushita Electric Industrial Co., Ltd. Composition of porcelain for voltage-dependent, non-linear resistor
GB8609324D0 (en) * 1986-04-16 1986-05-21 Micropore International Ltd Enclosing object
JPS6455301A (en) * 1987-08-26 1989-03-02 Sumitomo Heavy Industries Sintering method
US5130689A (en) * 1989-05-09 1992-07-14 Leach & Garner Co. Intermetallic time-temperature integration fuse
US5379022A (en) * 1993-05-03 1995-01-03 Fluke Corporation Thermistor device with extended operating range

Also Published As

Publication number Publication date
JPH07192599A (en) 1995-07-28
DE59410123D1 (en) 2002-07-04
DE4330534A1 (en) 1995-03-16
US6133819A (en) 2000-10-17
EP0643401A3 (en) 1997-04-02
EP0643401A2 (en) 1995-03-15

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