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EP0226595B1 - Spark plug for internal combustion engines - Google Patents

Spark plug for internal combustion engines Download PDF

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Publication number
EP0226595B1
EP0226595B1 EP86902799A EP86902799A EP0226595B1 EP 0226595 B1 EP0226595 B1 EP 0226595B1 EP 86902799 A EP86902799 A EP 86902799A EP 86902799 A EP86902799 A EP 86902799A EP 0226595 B1 EP0226595 B1 EP 0226595B1
Authority
EP
European Patent Office
Prior art keywords
spark plug
insulating body
plug according
annular
dielectric component
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP86902799A
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German (de)
French (fr)
Other versions
EP0226595A1 (en
Inventor
Adalbert BÄUERLE
Ludwig BARTHELMÄ
Walter Benedikt
Werner Herden
Walter Holl
Gerhard Liebing
Jürgen SCHMATZ
Siegbert Schwab
Walter WÜRTH
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OFFERTA DI LICENZA AL PUBBLICO
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP0226595A1 publication Critical patent/EP0226595A1/en
Application granted granted Critical
Publication of EP0226595B1 publication Critical patent/EP0226595B1/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/40—Sparking plugs structurally combined with other devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/38—Selection of materials for insulation

Definitions

  • the invention relates to a spark plug according to the preamble of the main claim;
  • a spark plug which is known from DE-A-2 363 804
  • Such a spark plug is also described in the aforementioned DE-A-2 363 804, which additionally has a spark gap, which is also installed within the spark plug and is electrically in series with the spark gap.
  • DE-A-2 363 804 does not provide any information about an economically feasible and reliable embodiment of such a spark plug.
  • a spark plug with built-in capacitor is already known; the insulating body composed of several longitudinal sections of this spark plug has such an average dielectric constant that this spark plug has a capacitance of 20 to 100 pF, preferably 30 to 80 pF.
  • the capacitor of this spark plug has the task of reducing or suppressing the electromagnetic interference of the internal combustion engine and thus preventing interference with radio and television systems and the like.
  • the preamble of claim 1 is based on this document.
  • the spark plug according to the invention with the characterizing features of the main claim has the advantage that it is economically feasible and can even ignite lean fuel vapor-air mixtures in all operating states of an internal combustion engine safely and over a required service life.
  • the measures listed in the subclaims enable advantageous developments and improvements of the spark plug specified in the main claim. It when the separating surfaces of the insulating body concerned have a roughness depth Rz of less than 30 ⁇ m is particularly advantageous; this is e.g. B. accessible by means of a glaze. According to the German standard (DIN 4768), the roughness depth Rz is to be understood as the mean value from the individual roughnesses Zi ... Z5 of five successive individual measuring sections. Because of this type of mounting of the insulating body, no expensive sintering systems are required to connect the longitudinal sections of the insulating body, and nevertheless reliable storage of electrical energy in the spark plug is guaranteed.
  • gas gaps of 0.01 to 0 are present between the dielectric component and the components that are operatively connected to it (connecting bolts, metal housing) , 50 mm, but preferably left from 0.05 to 0.30 mm; air is preferably used as the gas.
  • the spark plug 10 shown in the figure has a substantially tubular metal housing 11, which has on its outside as a means for installing this spark plug 10 in a motor head, not shown, a screw thread 12, a key hexagon 13 and a sealing ring 14.
  • this metal housing 11 has a hook-shaped ground electrode 15, which in the present example is designed as a welded wire, but can also be of a different configuration; Instead of a single ground electrode 15, depending on the application, a plurality of such ground electrodes can also be attached to the metal housing 11.
  • the metal housing 11 comprises, in a known manner, a rotationally symmetrical electrical insulating body 17 which usually protrudes from the through bore 16 of the metal housing 11 on the connection side.
  • This electrical insulating body 17 is divided into a plurality of longitudinal sections, specifically in the insulating body head 17/1 protruding on the connection side from the metal housing 11, an annular electrical insulating element 17/2 adjoining the insulating body head 17/1 on the combustion chamber side and the electrical insulating element on the combustion chamber side 17/2 adjoining dielectric component 17/3 of a capacitor 18, a second electrical insulation element 17/4 adjoining the dielectric component 17/3 on the combustion chamber side and an insulating body shaft 17/5 adjoining the second electrical insulation element 17/4 on the combustion chamber side, which preferably has the combustion chamber side from the metal housing 11 protruding insulator 17/6.
  • the insulating body head 17/1 is known to consist essentially of aluminum oxide, has on its surface a number of annular grooves 19 as a so-called leakage current barrier, is coaxial with the longitudinal bore 16 of the Me Tallgeophuses 11 extending through hole 20 and has a combustion chamber-side end portion which is designed as a flange 21.
  • the end surface of the insulating body head 17/1 remote from the combustion chamber is designated by 22, and the end surface of this insulating body head 17/1 on the combustion chamber side, which extends transversely to the longitudinal axis of the insulating body 17, is designated as the separating surface 23.
  • This separating surface 23 of the insulating body head 17/1 has a surface, the roughness Rz of which should be as small as 30 lL m, preferably even less than 5 ⁇ m; this lower roughness depth can best be achieved if a glaze (not shown) is applied to this surface, which has a layer thickness of less than 40 ⁇ m and which can be produced, for example, from a commercially available glass paste No. 9137 from Dupont.
  • the two electrical insulating elements 17/2 and 17/4 consist of a material which is rubber-elastic at all temperatures occurring in this area of the spark plug 10.
  • Such an electrical insulating element 17/2 or 17/4 can consist, for example, of an annular plate made of silicone rubber, which for example has a thickness of 1 mm and a Shore A hardness of 50.
  • the thickness of such electrical insulating elements 17/2, 17/4 can also be between 0.1 to 2 mm.
  • a material can also be used, which is applied in a liquid, soft or viscous manner to a separating surface (e.g. position 23) and, after the longitudinal sections 17/1 to 17/5 of the insulating body 17 have been joined together, if necessary a post-treatment (e.g.
  • a material suitable for this can be, for example, an epoxy resin or the like, which is adjusted accordingly with regard to the elasticity and to which fillers (e.g. aluminum oxide, talc, silicate) have optionally been added in a known manner in order to compensate for the different thermal expansion behavior of the longitudinal sections of the insulating body 17 involved are.
  • fillers e.g. aluminum oxide, talc, silicate
  • the electrical insulation element 17/2 is connected to the dielectric component 17/3, which belongs to the condenser 18, is of tubular configuration, has a through hole 20/1 running coaxially with the through hole 20 of the insulator head 17/1, with its separation surface remote from the combustion chamber 24/1 is firmly against the electrical insulating element 17/2 and with its combustion chamber-side separating surface 24/2 is firmly against the second electrical insulating element 17/4.
  • These two separating surfaces 24/1 and 24/2 of the dielectric component 17/3 also have a roughness depth R z that is as low as described above for the separating surface 23 of the insulating body head 17/1, and can also be provided with a corresponding glaze (not shown) may be coated.
  • the peripheral surface 25 of the dielectric component 17/3 preferably has a diameter which is slightly smaller than the diameter of the flange 21 of the insulating body head 17/1; Both this circumferential surface 25 and the surface of the through hole 20/1 of this dielectric component 17/3 are provided with a surface coating (not specially marked) which supports the electrical contact and which can consist, for example, of a silver-palladium alloy and is 10 ⁇ m thick .
  • the dielectric component 17/3 consists of a material with a dielectric constant of 100 to 500; a suitable substance is commercially available, for example, from the Japanese company Murata (type QQ or UF) and can consist, for example, of a mixture of calcium titanate, strontium titanate, bismuth oxide and lead titanate or even only of calcium titanate and strontium titanate.
  • This dielectric component 17/3 is dimensioned such that the finished spark plug 10 has a capacitance of 120 to 500 pF, but preferably has a capacitance of 200 to 400 pF.
  • the electrical insulation element 17/4 which adjoins the dielectric component 17/3 on the combustion chamber side, is followed next by the insulation body shaft 17/5, the end section remote from the combustion chamber is designed as a flange 26 and which is equipped with a through-bore 20/2; the through bore 20/2 has a shoulder 27 facing the connection side of the spark plug 10.
  • the insulating body shaft 17/5 also has on its outside an annular shoulder 28 which is directed towards the combustion chamber and forms the transition to the so-called insulating body foot 17/6; with this annular shoulder 28, the insulating body shaft 17/5 rests on an annular shoulder 30 located in the longitudinal bore 16 of the metal housing 11 via a so-called inner sealing ring 29.
  • the insulating body shaft 17/5 like the insulating body head 17/1, essentially consists of sintered aluminum oxide or similar material.
  • the through hole 20 of the insulating body head 17/1, the through hole 20/1 of the dielectric component 17/3 and the through hole 20/2 in the insulating body shaft 17/5 run coaxially to one another.
  • a metallic connecting bolt 31 is arranged, which carries a connection thread 32 on its end section remote from the combustion chamber and protrudes from the insulating body head 17/1 away from the combustion chamber, with its end section 31/1 on the combustion chamber side into the through hole 20/2 of the insulating body shaft 17/5 dips and has a roller-like central section 31/2, which has a slightly larger outer diameter than the area remote from the combustion chamber and also the area of the connecting bolt 31 on the combustion chamber side; the transition from the roller-like central section 31/2 to the two end sections of the connecting bolt 31 is preferably frustoconical, and accordingly the through hole 20 of the insulating body head 17/1 and the through hole 20/2 of the insulating body shaft 17/5 are adapted.
  • a known electrically conductive glass melt flux 35 is introduced between the central electrode head 33/1 and the combustion chamber-side end section 31/1 of the connecting bolt 31 - as described, for . B. is known from US-A-3 360 676; Anchoring means, which have not been further identified here, are preferably attached to the combustion chamber-side end section 31/1 of the connecting bolt 31 and also to the central electrode head 33/1 for the electrically conductive glass melt flux 35.
  • a contact sleeve 36/1 between the surfaces involved or 36/2 which can consist, for example, of a steel mesh with a small mesh size (eg 200 to 300 ⁇ m) and is 0.1 to 0.5 mm thick.
  • the contact sleeves 36/1 or 36/2 can stand on the combustion chamber-side electrical insulation element 17/4, which is arranged between the combustion chamber-side separating surface 24/2 of the dielectric component 17/3 and the combustion chamber end face of the insulating body shaft 17/5, which is designated as parting surface 37.
  • a gas gap of a certain width is of considerable advantage for the wear of the electrodes and possibly also for the wear of a spark slide of such spark plugs; this measure would therefore result in a longer lifespan and functional reliability of these spark plugs and, moreover, a saving in manufacturing costs.
  • the reduced wear of the electrodes or a spark slide is due to the energy converted in the ring gaps - which function as secondary spark gaps - during the glow and arc phase of the spark, which relieves the main spark gap 34 between the central electrode 33 and the ground electrode 15.
  • the gas gap that lies between the dielectric component 17/3 and the connecting bolt 31 and / or also the gas gap that is located between the dielectric component 17/3 and the metal housing 11 should have a width of 0.01 and 0, 50 mm, but preferably between 0.05 and 0.30 mm; a gap of this size remains electrically conductive in a voltage range of 5,000 V to 500 V.
  • air is suitable as the gas; If other gases (e.g. nitrogen) are to be used for special cases, then the two annular electrical insulating elements 17/2 and 17/4 must be designed in such a way that they form a seal on the roller-like central section 31/2 and in the longitudinal bore 16 of the metal housing 11 concerns.
  • the end section of the metal housing 11 remote from the combustion chamber is designed as a flanged edge 38 and presses the insulator head 17/1 firmly onto the first electrical insulating element 17/2 via a flanged ring 39, which rests on the side of the flange 21 of the insulating body head 17/1 remote from the combustion chamber , which the dielectric component 17/3, the second electrical insulating element 17/4, the insulating body shaft 17/5 and the inner sealing ring 29 on the annular shoulder 30 in the longitudinal bore 16 of the metal housing 11 and thus ensures a firm bond of the listed components.
  • the metal housing 11 has also been subjected to the known heat shrinking process (see, for example, US Pat. No. 2,111,916), which is the result of the heat shrink area 40 of the metal housing 11 can be seen.
  • the capacitor 18 of this spark plug 10 is thus formed between the connecting bolt 31 and the metal housing 11 as capacitor electrodes and the dielectric component 17/3 and is connected in parallel to the spark gap 34 of the spark plug 10; the required properties of this capacitor 18 have already been described above.
  • a spark gap is additionally installed in the end section 31/1 of the connecting block 31, which spark gap is preferably tightly encapsulated and how it z. B. is known in principle from US-A-3 742 280.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Spark Plugs (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)

Abstract

A spark plug (10) which is also suited for igniting lean vaporized fuel/air mixtures. This spark plug (10) surrounds, with its annular metal casing (11), an insulating body (17) which is separated into longitudinal sections and as usual contains, in the hole (20) which passes through it, an attachment bolt (31) and a central electrode (33). A longitudinal section (17/3) of the insulating body (17), surrounded by the metal casing (11), consists of dielectric material and forms, jointly with the metal casing (11) and the attachment bolt (31/2), a capacitor (18) having a capacity of 120 to 500 pF, and essentially 200 to 400 pF. In order to prevent, in the regions of the mating surfaces of the insulating body, flashovers between the attachment bolt (31/2) and the metal casing (11), and to economize costly sintering equipment for connecting the longitudinal sections of the insulating body, annular electrical insulating elements (17/2, 17/4) are arranged between the mating surfaces (24/1, 24,2), which have a rubber-like elasticity at all temperatures of the spark plug (e.g. silicon rubber, epoxy resin).

Description

Stand der TechnikState of the art

Die Erfindung geht aus von einer Zündkerze nach der Gattung des Hauptanspruchs; eine derartige Zündkerze, die aus der DE-A-2 363 804 bekannt ist, hat einen Kondensator, der in der Zündkerze mit eingebaut und elektrisch parallel zur Funkenstrecke angeordnet ist. Dieser Kondensator soll nahe der Funkenstrecke der Zündkerze genügend Energie speichern, so daß beim Funkendurchbruch an der Funkenstrecke der Zündkerze die energiereiche Anfangsphase des Funkens eine sichere Zündung des in der Brennkraftmaschine befindlichen Kraftstoffdampf-Luft-Gemisches bewirkt. Beschrieben ist in der genannten DE-A-2 363 804 auch eine derartige Zündkerze, die zusätzlich noch eine Vorfunkenstrecke besitzt, welche ebenfalls innerhalb der Zündkerze eingebaut ist und mit der Funkenstrecke elektrisch in Reihe liegt. Der genannten DE-A-2 363 804 sind aber keine Hinweise über eine wirtschaftlich realisierbare und funktionssichere Ausführungsform einer solchen Zündkerze zu entnehmen.The invention relates to a spark plug according to the preamble of the main claim; Such a spark plug, which is known from DE-A-2 363 804, has a capacitor which is installed in the spark plug and is arranged electrically parallel to the spark gap. This capacitor should store enough energy near the spark gap of the spark plug so that when the spark breaks through the spark gap of the spark plug, the high-energy initial phase of the spark causes the ignition of the fuel vapor-air mixture in the internal combustion engine. Such a spark plug is also described in the aforementioned DE-A-2 363 804, which additionally has a spark gap, which is also installed within the spark plug and is electrically in series with the spark gap. However, DE-A-2 363 804 does not provide any information about an economically feasible and reliable embodiment of such a spark plug.

Auch aus der DE-A-3 404 081 ist schon eine Zünderze mit eingebautem Kondensator bekannt; der aus mehreren Längsabschnitten zusammengesetzte Isolierkörper dieser Zündkerze hat eine solche durchschnittliche Dielektrizitätskonstante, so daß diese Zündkerze eine Kapazität von 20 bis 100 pF, bevorzugt von 30 bis 80 pF hat. Der . Kondensator dieser Zündkerze hat dabei die Aufgabe, die elektromagnetische Interferenz der Brennkraftmaschine zu reduzieren bzw. zu unterdrücken und somit Störungen bei Radio- und Fernsehanlagen und ähnlichem zu verhindern. Der Oberbegriff des Anspruchs 1 geht von dieser Druckschrift aus.From DE-A-3 404 081 a spark plug with built-in capacitor is already known; the insulating body composed of several longitudinal sections of this spark plug has such an average dielectric constant that this spark plug has a capacitance of 20 to 100 pF, preferably 30 to 80 pF. The . The capacitor of this spark plug has the task of reducing or suppressing the electromagnetic interference of the internal combustion engine and thus preventing interference with radio and television systems and the like. The preamble of claim 1 is based on this document.

Vorteile der ErfindungAdvantages of the invention

Die erfindungsgemäße Zündkerze mit den kennzeichnenden Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß sie wirtschaftlich realisierbar ist und selbst magere Kraftstoffdampf-Luft-Gemische bei allen Betriebszuständen einer Brennkraftmaschine sicher und über eine erforderliche Lebensdauer zu zünden vermag.The spark plug according to the invention with the characterizing features of the main claim has the advantage that it is economically feasible and can even ignite lean fuel vapor-air mixtures in all operating states of an internal combustion engine safely and over a required service life.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen der im Hauptanspruch angegebenen Zündkerze möglich. Besonders vorteilhaft ist es, wenn die betroffenen Trennflächen des Isolierkörpers eine Rauhtiefe Rz von weniger als 30 µm haben; dieses ist z. B. erreichbar mittels einer Glasur. Unter Rauhtiefe Rz ist gemäß deutscher Norm (DIN 4768) der Mittelwert aus den Einzelrauhheiten Zi ... Z5 fünf aufeinanderfolgender Einzelmeßstrecken zu verstehen. Aufgrund dieser Art der Montage des Isolierkörpers sind keine teueren Sinteranlagen zum Verbinden der IsolierkörperLängsabschnitte erforderlich und es wird dennoch eine zuverlässige Speicherung elektrischer Energie in der Zündkerze gewährleistet.The measures listed in the subclaims enable advantageous developments and improvements of the spark plug specified in the main claim. It when the separating surfaces of the insulating body concerned have a roughness depth Rz of less than 30 μm is particularly advantageous; this is e.g. B. accessible by means of a glaze. According to the German standard (DIN 4768), the roughness depth Rz is to be understood as the mean value from the individual roughnesses Zi ... Z5 of five successive individual measuring sections. Because of this type of mounting of the insulating body, no expensive sintering systems are required to connect the longitudinal sections of the insulating body, and nevertheless reliable storage of electrical energy in the spark plug is guaranteed.

Zur Verringerung des Elektroden- und gegebenenfalls eines Funkengleitbahn-Verschleißes und damit der Verbesserung der Funktionssicherheit und Lebensdauer bei derartigen Zündkerzen ist es vorteilhaft, wenn zwischen dem dielektrischen Bauteil und den damit in Wirkverbindung stehenden Bauteilen (Anschlußbolzen, Metallgehäuse) Gasspalte von 0,01 bis 0,50 mm, vorzugsweise jedoch von 0,05 bis 0,30 mm belassen sind; als Gas findet bevorzugt Luft Verwendung.In order to reduce the wear on the electrodes and, if applicable, spark slide paths and thus improve the functional reliability and service life of such spark plugs, it is advantageous if gas gaps of 0.01 to 0 are present between the dielectric component and the components that are operatively connected to it (connecting bolts, metal housing) , 50 mm, but preferably left from 0.05 to 0.30 mm; air is preferably used as the gas.

Zeichnungdrawing

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert; die Figur zeigt einen Längsschnitt durch eine vergrößert dargestellte Zündkerze nach der Erfindung.An embodiment of the invention is shown in the drawing and explained in more detail in the following description; the figure shows a longitudinal section through an enlarged spark plug according to the invention.

Beschreibung des AusführungsbeispielesDescription of the embodiment

Die in der Figur dargestellte Zündkerze 10 besitzt ein im wesentlichen rohrförmiges Metallgehäuse 11, das an seiner Außenseite als Mittel für den Einbau dieser Zündkerze 10 in einen nicht dargestellten Motorkopf ein Einschraubgewinde 12, ein Schlüsselsechskant 13 und einen Dichtring 14 aufweist. Im Bereich seines brennraumseitigen Endes hat dieses Metallgehäuse 11 eine hakenförmige Masseelektrode 15, welche im vorliegenden Beispiel als angeschweißter Draht ausgebildet ist, jedoch auch von anderer Konfiguration sein kann; anstelle einer einzigen Masselektrode 15 können je nach Anwendungsfall auch mehrere derartiger Masseelektroden am Metallgehäuse 11 angebracht sein. Das Metallgehäuse 11 umfaßt in seiner Längsbohrung 16 in bekannter Weise einen rotationssymmetrischen Elektroisolierkörper 17, der üblicherweise anschlußseits aus der Durchgangsbohrung 16 des Metallgehäuses 11 herausragt. Dieser Elektroisolierkörper 17 ist in mehrere Längsabschnitte unterteilt, und zwar in den anschlußseits aus dem Metallgehäuse 11 herausragenden Isolierkörper-Kopf 17/1, ein sich brennraumseits an den Isolierkörper-Kopf 17/1 anschließendes, ringförmiges Elektroisolierelement 17/2, dem sich brennraumseits dem Elektroisolierelement 17/2 anschließenden dielektrischen Bauteil 17/3 eines Kondensators 18, einem zweiten, sich den dielektrischen Bauteil 17/3 brennraumseits anschließenden Elektroisolierelement 17/4 und einem sich dem zweiten Elektroisolierelement 17/4 brennraumseits anschließenden Isolierkörper-Schaft 17/5 mit dem bevorzugterweise brennraumseits aus dem Metallgehäuse 11 herausragenden Isolierkörper-Fuß 17/6.The spark plug 10 shown in the figure has a substantially tubular metal housing 11, which has on its outside as a means for installing this spark plug 10 in a motor head, not shown, a screw thread 12, a key hexagon 13 and a sealing ring 14. In the area of its end on the combustion chamber side, this metal housing 11 has a hook-shaped ground electrode 15, which in the present example is designed as a welded wire, but can also be of a different configuration; Instead of a single ground electrode 15, depending on the application, a plurality of such ground electrodes can also be attached to the metal housing 11. In its longitudinal bore 16, the metal housing 11 comprises, in a known manner, a rotationally symmetrical electrical insulating body 17 which usually protrudes from the through bore 16 of the metal housing 11 on the connection side. This electrical insulating body 17 is divided into a plurality of longitudinal sections, specifically in the insulating body head 17/1 protruding on the connection side from the metal housing 11, an annular electrical insulating element 17/2 adjoining the insulating body head 17/1 on the combustion chamber side and the electrical insulating element on the combustion chamber side 17/2 adjoining dielectric component 17/3 of a capacitor 18, a second electrical insulation element 17/4 adjoining the dielectric component 17/3 on the combustion chamber side and an insulating body shaft 17/5 adjoining the second electrical insulation element 17/4 on the combustion chamber side, which preferably has the combustion chamber side from the metal housing 11 protruding insulator 17/6.

Der Isolierkörper-Kopf 17/1 besteht bekannterweise im wesentlichen aus Aluminiumoxid, besitzt auf seiner Oberfläche eine Anzahl von Ringnuten 19 als sogenannte Kriechstrombarriere, ist mit einer koaxial zur Längsbohrung 16 des Metallgehäuses 11 verlaufenden Durchgangsbohrung 20 versehen und besitzt einen brennraumseitigen Endabschnitt, der als Flansch 21 ausgebildet ist. Die brennraumferne Stirnfläche des Isolierkörper-Kopfes 17/1 ist mit 22 bezeichnet und die brennraumseitige Stirnfläche dieses Isolierkörpers-Kopfes 17/1, die quer zur Längsachse des Isolierkörpers 17 verläuft, ist als Trennfläche 23 bezeichnet. Diese Trennfläche 23 des Isolierkörper-Kopfes 17/1 hat eine Oberfläche, deren Rauhtiefe Rz möglichst kleiner als 30 lLm, bevorzugt sogar von weniger als 5 µm haben sollte; diese geringere Rauhtiefe läßt sich am besten dadurch erzielen, wenn man auf dieser Oberfläche eine Glasur (nicht dargestellt) aufbringt, die eine Schichtdicke von unter 40 µm hat und die beispielsweise aus einer handelsüblichen Glaspaste Nr. 9137 der Firma Dupont herstellbar ist.The insulating body head 17/1 is known to consist essentially of aluminum oxide, has on its surface a number of annular grooves 19 as a so-called leakage current barrier, is coaxial with the longitudinal bore 16 of the Me Tallgehäuses 11 extending through hole 20 and has a combustion chamber-side end portion which is designed as a flange 21. The end surface of the insulating body head 17/1 remote from the combustion chamber is designated by 22, and the end surface of this insulating body head 17/1 on the combustion chamber side, which extends transversely to the longitudinal axis of the insulating body 17, is designated as the separating surface 23. This separating surface 23 of the insulating body head 17/1 has a surface, the roughness Rz of which should be as small as 30 lL m, preferably even less than 5 μm; this lower roughness depth can best be achieved if a glaze (not shown) is applied to this surface, which has a layer thickness of less than 40 μm and which can be produced, for example, from a commercially available glass paste No. 9137 from Dupont.

Die beiden Elektroisolierelemente 17/2 und 17/4, bestehen aus einem Material, das bei allen in diesem Bereich der Zündkerze 10 auftretenden Temperaturen gummielastisch ist. Ein solches Elektroisolierelement 17/2 bzw. 17/4 kann beispielsweise aus einer ringförmigen Platte aus Silicongummi bestehen, die beispielsweise eine Dicke von 1 mm und eine Shore-A-Härte von 50 hat. Die Dicke derartiger Elektroisolierelemente 17/2, 17/4 kann aber auch zwischen 0,1 bis 2 mm liegen. Anstelle des Silicongummis kann aber auch ein Material treten, das man flüssig, weich oder viskos auf eine Trennfläche (z. B. Position 23) aufträgt und nach dem Zusammenfügen der beteiligten Längsabschnitte 17/1 bis 17/5 des Isolierkörpers 17 gegebenenfalls einer Nachbehandlung (z. B. Polymerisation) unterwirft; ein hierfür geeignetes Material kann beispielsweise ein Epoxidharz oder ähnliches sein, welches hinsichtlich der Elastizität entsprechend eingestellt ist und dem gegebenenfalls in bekannter Weise Füllstoffe (z. B. Aluminiumoxid, Talkum, Silikat) zur Kompensation des unterschiedlichen Wärmeausdehnungsverhaltens der beteiligten Längsabschnitte des Isolierkörpers 17 hinzugefügt worden sind.The two electrical insulating elements 17/2 and 17/4 consist of a material which is rubber-elastic at all temperatures occurring in this area of the spark plug 10. Such an electrical insulating element 17/2 or 17/4 can consist, for example, of an annular plate made of silicone rubber, which for example has a thickness of 1 mm and a Shore A hardness of 50. The thickness of such electrical insulating elements 17/2, 17/4 can also be between 0.1 to 2 mm. Instead of the silicone rubber, a material can also be used, which is applied in a liquid, soft or viscous manner to a separating surface (e.g. position 23) and, after the longitudinal sections 17/1 to 17/5 of the insulating body 17 have been joined together, if necessary a post-treatment ( e.g. polymerization); a material suitable for this can be, for example, an epoxy resin or the like, which is adjusted accordingly with regard to the elasticity and to which fillers (e.g. aluminum oxide, talc, silicate) have optionally been added in a known manner in order to compensate for the different thermal expansion behavior of the longitudinal sections of the insulating body 17 involved are.

Dem Elektroisolierelement 17/2 schließt sich brennraumseits das dielektrische Bauteil 17/3 an, das zum Kondensator 18 gehört, von rohrförmiger Konfiguration ist, eine gleichachsig zur Durchgangsbohrung 20 des Isolierkörper-Kopfes 17/1 verlaufende Durchgangsbohrung 20/1 aufweist, mit seiner brennraumfernen Trennfläche 24/1 fest am Elektroisolierelement 17/2 anliegt und mit seiner brennraumseitigen Trennfläche 24/2 fest am zweiten Elektroisolierelement 17/4 aufliegt. Auch diese beiden Trennflächen 24/1 und 24/2 des dielektrischen Bauteils 17/3 weisen eine so geringe Rauhtiefe Rz auf wie es auch oben bei der Trennfläche 23 des Isolierkörper-Kopfes 17/1 beschrieben ist, und können auch mit einer entsprechenden Glasur (nicht dargestellt) beschichtet sein. Die Umfangsfläche 25 des dielektrischen Bauteiles 17/3 hat bevorzugterweise einen Durchmesser, der geringfügig kleiner ist als der Durchmesser des Flansches 21 des Isolierkörper-Kopfes 17/1; sowohl diese Umfangsfläche 25 als auch die Oberfläche der Durchgangsbohrung 20/1 dieses dielektrischen Bauteils 17/3 sind mit einer den elektrischen Kontakt unterstützenden Oberflächenbeschichtung (nicht extra gekennzeichnet) versehen, die beispielsweise aus einer Silber-Palladium-Legierung bestehen kann und 10 µm dick ist. Das dielektrische Bauteil 17/3 besteht aus einem Material mit einer Dielektrizitätszahl er von 100 bis 500; ein geeigneter Stoff ist beispielsweise von der japanischen Firma Murata handelsüblich erhältlich (Typ QQ oder UF) und kann beispielsweise aus einer Mischung von Calciumtitanat, Strontiumtitanat, Wismutoxid und Bleititanat bestehen oder auch nur aus Calciumtitanat und Strontiumtitanat. Dieses dielektrische Bauteil 17/3 ist so bemessen, daß die fertige Zündkerze 10 eine Kapazität von 120 bis 500 pF aufweist, bevorzugt aber eine Kapazität von 200 bis 400 pF hat.On the combustion chamber side, the electrical insulation element 17/2 is connected to the dielectric component 17/3, which belongs to the condenser 18, is of tubular configuration, has a through hole 20/1 running coaxially with the through hole 20 of the insulator head 17/1, with its separation surface remote from the combustion chamber 24/1 is firmly against the electrical insulating element 17/2 and with its combustion chamber-side separating surface 24/2 is firmly against the second electrical insulating element 17/4. These two separating surfaces 24/1 and 24/2 of the dielectric component 17/3 also have a roughness depth R z that is as low as described above for the separating surface 23 of the insulating body head 17/1, and can also be provided with a corresponding glaze (not shown) may be coated. The peripheral surface 25 of the dielectric component 17/3 preferably has a diameter which is slightly smaller than the diameter of the flange 21 of the insulating body head 17/1; Both this circumferential surface 25 and the surface of the through hole 20/1 of this dielectric component 17/3 are provided with a surface coating (not specially marked) which supports the electrical contact and which can consist, for example, of a silver-palladium alloy and is 10 μm thick . The dielectric component 17/3 consists of a material with a dielectric constant of 100 to 500; a suitable substance is commercially available, for example, from the Japanese company Murata (type QQ or UF) and can consist, for example, of a mixture of calcium titanate, strontium titanate, bismuth oxide and lead titanate or even only of calcium titanate and strontium titanate. This dielectric component 17/3 is dimensioned such that the finished spark plug 10 has a capacitance of 120 to 500 pF, but preferably has a capacitance of 200 to 400 pF.

Dem brennraumseits sich dem dielektrischen Bauteil 17/3 anschließenden Elektroisolierelement 17/4 folgt als nächstes Bauteil der Isolierkörper-Schaft 17/5, dessen brennraumferner Endabschnitt als Flansch 26 ausgebildet ist und der mit einer Durchgangsbohrung 20/2 ausgestattet ist; die Durchgangsbohrung 20/2 besitzt eine zur Anschlußseite der Zündkerze 10 weisende Schulter 27. Der Isolierkörper-Schaft 17/5 hat auch an seiner Außenseite einen ringförmigen Absatz 28, der brennraumseits gerichtet ist und den Übergang zum sogenannten Isolierkörper-Fuß 17/6 bildet; mit diesem ringförmigen Absatz 28 liegt der Isolierkörper-Schaft 17/5 über einen sogenannten inneren Dichtring 29 auf einer in der Längsbohrung 16 des Metallgehäuses 11 befindlichen Ringschulter 30 auf. Der Isolierkörper- Schaft 17/5 besteht ebenso wie der Isolierkörper-Kopf 17/1 im wesentlichen aus gesintertem Aluminiumoxid oder ähnlichem Material.The electrical insulation element 17/4, which adjoins the dielectric component 17/3 on the combustion chamber side, is followed next by the insulation body shaft 17/5, the end section remote from the combustion chamber is designed as a flange 26 and which is equipped with a through-bore 20/2; the through bore 20/2 has a shoulder 27 facing the connection side of the spark plug 10. The insulating body shaft 17/5 also has on its outside an annular shoulder 28 which is directed towards the combustion chamber and forms the transition to the so-called insulating body foot 17/6; with this annular shoulder 28, the insulating body shaft 17/5 rests on an annular shoulder 30 located in the longitudinal bore 16 of the metal housing 11 via a so-called inner sealing ring 29. The insulating body shaft 17/5, like the insulating body head 17/1, essentially consists of sintered aluminum oxide or similar material.

Wie oben schon beschrieben, verlaufen die Durchgangsbohrung 20 des Isolierkörper-Kopfes 17/1, die Durchgangsbohrung 20/1 des dielektrischen Bauteils 17/3 und die Durchgangsbohrung 20/2 im Isolierkörper-Schaft 17/5 koaxial zueinander. Innerhalb dieser Durchgangsbohrungen 20, 20/1 und 20/2 ist ein metallischer Anschlußbolzen 31 angeordnet, welcher an seinem brennraumfernen Endabschnitt ein Anschlußgewinde 32 trägt und brennraumfern aus dem Isolierkörper-Kopf 17/1 herausragt, mit seinem brennraumseitigen Endabschnitt 31/1 in die Durchgangsbohrung 20/2 des Isolierkörper-Schaftes 17/5 taucht und einen walzenartigen Mittelabschnitt 31/2 besitzt, welcher einen etwas größeren Außendurchmesser hat als der brennraumferne und auch der brennraumseitige Bereich des Anschlußbolzens 31; der Übergang des walzenartigen Mittelabschnittes 31/2 zu den beiden Endabschnitten des Anschlußbolzens 31 ist bevorzugt kegelstumpfförmig ausgebildet und dementsprechend sind auch die Durchgangsbohrung 20 des lsolierkörper-Kopfes 17/1 bzw. die Durchgangsbohrung 20/2 des Isolierkörper-Schaftes 17/5 angepaßt.As already described above, the through hole 20 of the insulating body head 17/1, the through hole 20/1 of the dielectric component 17/3 and the through hole 20/2 in the insulating body shaft 17/5 run coaxially to one another. Within these through bores 20, 20/1 and 20/2, a metallic connecting bolt 31 is arranged, which carries a connection thread 32 on its end section remote from the combustion chamber and protrudes from the insulating body head 17/1 away from the combustion chamber, with its end section 31/1 on the combustion chamber side into the through hole 20/2 of the insulating body shaft 17/5 dips and has a roller-like central section 31/2, which has a slightly larger outer diameter than the area remote from the combustion chamber and also the area of the connecting bolt 31 on the combustion chamber side; the transition from the roller-like central section 31/2 to the two end sections of the connecting bolt 31 is preferably frustoconical, and accordingly the through hole 20 of the insulating body head 17/1 and the through hole 20/2 of the insulating body shaft 17/5 are adapted.

In demjenigen Bereich der Durchgangsbohrung 20/2 des Isolierkörper-Schaftes 17/5, der vom lsolierkörper-Fuß 17/6 im wesentlichen gebildet ist, befindet sich die metallische Mittelelektrode 33, welche mit ihrem brennraumfernen Kopf 33/1 auf der ringförmigen Schulter 27 in der Durchgangsbohrung 20/2 des Isolierkörper-Schaftes 17/5 aufliegt; dem brennraumnahen Ende der Mittelelektrode 33 steht mit Abstand, der sogenannten Funkenstrecke 34, die eine Masseelektrode 15 oder auch mehrere Masseelektroden gegenüber.In that area of the through hole tion 20/2 of the insulating body shaft 17/5, which is essentially formed by the insulating body foot 17/6, there is the metallic center electrode 33 which, with its head 33/1 remote from the combustion chamber, on the annular shoulder 27 in the through bore 20 / 2 of the insulating body shaft 17/5 rests; the end of the center electrode 33 near the combustion chamber is at a distance, the so-called spark gap 34, which is opposite a ground electrode 15 or also a plurality of ground electrodes.

Zur gasdichten Abdichtung der Durchgangsbohrung 20/2 und auch zur elektrischen Verbindung des Anschlußbolzens 31 mit der Mittelelektrode 33 ist zwischen den Mittelelektroden-Kopf 33/1 und den brennraumseitigen Endabschnitt 31/1 des Anschlußbolzens 31 eine bekannte elektrisch leitende Glasschmelzflußmasse 35 eingebracht - wie sie z. B. aus der US-A-3 360 676 bekannt ist; sowohl am brennraumseitigen Endabschnitt 31/1 des Anschlußbolzens 31 auch als am Mittelelektroden-Kopf 33/1 sind für die elektrisch leitende Glasschmelzflußmasse 35 bevorzugterweise Verankerungsmittel angebracht, die hier nicht weiter gekennzeichnet worden sind.For gas-tight sealing of the through hole 20/2 and also for the electrical connection of the connecting bolt 31 to the central electrode 33, a known electrically conductive glass melt flux 35 is introduced between the central electrode head 33/1 and the combustion chamber-side end section 31/1 of the connecting bolt 31 - as described, for . B. is known from US-A-3 360 676; Anchoring means, which have not been further identified here, are preferably attached to the combustion chamber-side end section 31/1 of the connecting bolt 31 and also to the central electrode head 33/1 for the electrically conductive glass melt flux 35.

Zur sicheren elektrischen Verbindung zwischen dem walzenartigen Mittelabschnitt 31/2 des Anschlußbolzens 31 und dem dielektrischen Bauteil 17/3 sowie auch für die gute elektrische Verbindung zwischen dem dielektrischen Bauteil 17/3 und dem Metallgehäuse 11 ist zwischen den beteiligten Flächen jeweils eine Kontakthülse 36/1 bzw. 36/2 angeordnet, welche beispielsweise aus einem Stahlgitter geringer Maschenweite (z. B. 200 bis 300 µm) bestehen kann und 0,1 bis 0,5 mm dick ist. Die Kontakthülsen 36/1 bzw. 36/2 können dabei auf dem brennraumseitigen Elektroisolierelement 17/4 aufstehen, welches zwischen der brennraumseitigen Trennfläche 24/2 des dielektrischen Bauteils 17/3 und der brennraumfernen Stirnfläche des Isolierkörper-Schaftes 17/5 angeordnet ist, welche als Trennfläche 37 bezeichnet ist.For a secure electrical connection between the roller-like middle section 31/2 of the connecting bolt 31 and the dielectric component 17/3 and also for the good electrical connection between the dielectric component 17/3 and the metal housing 11, there is a contact sleeve 36/1 between the surfaces involved or 36/2, which can consist, for example, of a steel mesh with a small mesh size (eg 200 to 300 µm) and is 0.1 to 0.5 mm thick. The contact sleeves 36/1 or 36/2 can stand on the combustion chamber-side electrical insulation element 17/4, which is arranged between the combustion chamber-side separating surface 24/2 of the dielectric component 17/3 and the combustion chamber end face of the insulating body shaft 17/5, which is designated as parting surface 37.

Anstelle dieser Kontakthülsen 36/1 und 36/2 können aber auch andere den elektrischen Kontakt zwischen den beteiligten Teilen unterstützende Mittel Anwendung finden, so z. B. auch eine elektrisch leitfähige Gußmasse, Graphitpackungen oder ähnliches.Instead of these contact sleeves 36/1 and 36/2, other means supporting the electrical contact between the parts involved can also be used, for. B. also an electrically conductive casting compound, graphite packing or the like.

Es hat sich jedoch herausgestellt, daß anstelle der genannten Kontakthülsen 36/1 bzw. 36/2 oder elektrischen Massen zwischen dem dielektrischen Bauteil 17/3 und dem Anschlußbolzen 31 bzw. dem Metallgehäuse 11 ein Gasspalt bestimmter Breite von erheblichem Vorteil für den Verschleiß der Elektroden und gegebenenfalls auch für den Verschleiß einer Funkengleitbahn derartiger Zündkerzen ist; diese Maßnahme würde also eine längere Lebensdauer und Funktionssicherheit dieser Zündkerzen und darüber hinaus eine Einsparung von Herstellkosten bewirken. Zurückzuführen ist der verringerte Verschleiß der Elektroden bzw. einer Funkengleitbahn auf die in den Ringspalten - die als Nebenfunkenstrecken funktionieren - während der Glimmund Bogenphase des Funkens umgesetzten Energie, von welcher die Hauptfunkenstrecke 34 zwischen Mittelelektrode 33 und Masseelektrode 15 enlastet wird. Der Gasspalt, der zwischen dem dielektrischen Bauteil 17/3 und dem Anschlußbolzen 31 liegt, und/oder auch der Gasspalt, der sich zwischen dem dielektrischen Bauteil 17/3 und dem Metallgehäuse 11 befindet, sollte dabei eine Breite von 0,01 und 0,50 mm, bevorzugt jedoch zwischen 0,05 und 0,30 mm haben; ein Spalt dieser Größenordnung bleibt in einem Spannungsbereich von 5 000 V bis 500 V elektrisch leitend. Als Gas ist im einfachsten Falle Luft geeignet; sollen für spezielle Fälle andere Gase (z. B. Stickstoff) Verwendung finden, dann müssen die beiden ringförmigen Elektroisolierelemente 17/2 und 17/4 derart ausgebildet sein, so daß sie abdichtend am walzenartigen Mittelabschnitt 31/2 und in der Längsbohrung 16 des Metallgehäuses 11 anliegen.However, it has been found that instead of the aforementioned contact sleeves 36/1 or 36/2 or electrical masses between the dielectric component 17/3 and the connecting bolt 31 or the metal housing 11, a gas gap of a certain width is of considerable advantage for the wear of the electrodes and possibly also for the wear of a spark slide of such spark plugs; this measure would therefore result in a longer lifespan and functional reliability of these spark plugs and, moreover, a saving in manufacturing costs. The reduced wear of the electrodes or a spark slide is due to the energy converted in the ring gaps - which function as secondary spark gaps - during the glow and arc phase of the spark, which relieves the main spark gap 34 between the central electrode 33 and the ground electrode 15. The gas gap that lies between the dielectric component 17/3 and the connecting bolt 31 and / or also the gas gap that is located between the dielectric component 17/3 and the metal housing 11 should have a width of 0.01 and 0, 50 mm, but preferably between 0.05 and 0.30 mm; a gap of this size remains electrically conductive in a voltage range of 5,000 V to 500 V. In the simplest case, air is suitable as the gas; If other gases (e.g. nitrogen) are to be used for special cases, then the two annular electrical insulating elements 17/2 and 17/4 must be designed in such a way that they form a seal on the roller-like central section 31/2 and in the longitudinal bore 16 of the metal housing 11 concerns.

Der brennraumferne Endabschnitt des Metallgehäuses 11 ist als Bördelrand 38 ausgebildet und drückt über einen Bördelring 39, welcher auf der brennraumfernen Seite des Flansches 21 des Isolierkörper-Kopfes 17/1 aufliegt, den Isolierkörper-Kopf 17/1 fest auf das erste Elektroisolierelement 17/2, das die dielektrische Bauteil 17/3, das zweite Elektroisolierelement 17/4, den IsolierkörperSchaft 17/5 und den inneren Dichtring 29 auf die Ringschulter 30 in der Längsbohrung 16 des Metallgehäuses 11 und sorgt damit für einen festen Verbund der aufgeführten Bauteile. Um auch den zwischen den vorstehend aufgezeigten Bauteilen und der Längsbohrung des Metallgehäuses 11 befindlichen Spalt gasdicht zu machen, ist das Metallgehäuse 11 zusätzlich noch dem bekannten Warmschrumpfprozeß unterworfen worden (siehe z. B. US-A-2 111 916), was am Warmschrumpfbereich 40 des Metallgehäuses 11 zu ersehen ist.The end section of the metal housing 11 remote from the combustion chamber is designed as a flanged edge 38 and presses the insulator head 17/1 firmly onto the first electrical insulating element 17/2 via a flanged ring 39, which rests on the side of the flange 21 of the insulating body head 17/1 remote from the combustion chamber , which the dielectric component 17/3, the second electrical insulating element 17/4, the insulating body shaft 17/5 and the inner sealing ring 29 on the annular shoulder 30 in the longitudinal bore 16 of the metal housing 11 and thus ensures a firm bond of the listed components. In order to also make the gap between the components shown above and the longitudinal bore of the metal housing 11 gas-tight, the metal housing 11 has also been subjected to the known heat shrinking process (see, for example, US Pat. No. 2,111,916), which is the result of the heat shrink area 40 of the metal housing 11 can be seen.

Der Kondensator 18 dieser Zündkerze 10 wird somit zwischen dem Anschlußbolzen 31 und dem Metallgehäuse 11 als Kondensatorelektroden und dem dielektrischen Bauteil 17/3 gebildet und ist parallel zur Funkenstrecke 34 der Zündkerze 10 geschaltet; die erforderlichen Eigenschaften dieses Kondensators 18 wurden weiter vorn bereits beschrieben.The capacitor 18 of this spark plug 10 is thus formed between the connecting bolt 31 and the metal housing 11 as capacitor electrodes and the dielectric component 17/3 and is connected in parallel to the spark gap 34 of the spark plug 10; the required properties of this capacitor 18 have already been described above.

Je nach Ausführungsform der jeweiligen Brennkraftmaschine kann es auch zweckmäßig sein, wenn im Endabschnitt 31/1 des Anschlußboclzens 31 zusätzlich noch eine Vorfunkenstrecke eingebaut ist, welche bevorzugt dicht eingekapselt ist und wie sie z. B. aus der US-A-3 742 280 prinzipiell bekannt ist.Depending on the embodiment of the respective internal combustion engine, it may also be expedient if a spark gap is additionally installed in the end section 31/1 of the connecting block 31, which spark gap is preferably tightly encapsulated and how it z. B. is known in principle from US-A-3 742 280.

Es sei abschließend nochmals besonders darauf hingewiesen, daß aufgrund der Elektroisolierelemente 17/2 und 17/4 ein Zusammensintern der drei keramischen Bauteile 17/1, 17/3 und 17/5 in großen und teueren Sinteranlagen entfällt, was für eine Fertigungslinie für die diesbezüglichen Zündkerzen einen erheblichen Vorteil darstellt.Finally, it should be particularly pointed out that, due to the electrical insulating elements 17/2 and 17/4, sintering together of the three ceramic components 17/1, 17/3 and 17/5 in large and expensive sintering plants is not necessary, which is a production line for the relevant ones Spark plugs represent a significant advantage.

Claims (10)

1. Spark plug (10) for internal combustion engines, having a tubular metal casing (11) which is provided with fixing means (12, 13, 14) for installation into an internal combustion engine, preferably bears at least one side electrode (15) on its end section on the combustionchamber side and has a longitudinal bore (16) by which at least one longitudinal section of an electrical insulating body (17) is gas-tightly surrounded which at least partially forms a dielectric component (18) connected operatively to the metal casing (11), and has a through bore (20) which sealingly surrounds a terminal stud (31) which is likewise operatively connected to the dielectric component (18) and is connected electrically on the combustion-chamber side to a central electrode (33) which is operatively connected via a spark gap (34) to the side electrode (15), of which there is at least one, characterized in that the insulating body (17) contains at least five separate longitudinal sections (17/1 to 17/5), of which one longitudinal section is the dielectric component (17/3), which imparts to the spark plug (10) a capacitance of 120 to 500 pF and is separated from the sections (17/1 and 17/5) of the insulating body (17) which adjoin on both sides in the longitudinal direction by means of annular electrical insulating elements (17/2 and 17/4 respectively) which rest firmly against the respective separating surfaces (23, 24/1, 24/2, 37) of the insulating body (17) and consist of a material which is of rubber-like elasticity at all temperatures occurring in this region of the spark plug (10).
2. Spark plug according to Claim 1, characterized in that it has a capacitance of 200 to 400 pF.
3. Spark plug according to Claim 1 or 2, characterized in that the annular electric insulating elements (17/2, 17/4) consist of silicone rubber.
4. Spark plug according to Claim 1 or 2, characterized in that the annular electric insulating elements (17/2, 17/4) consist of a material which has been applied to the separating surfaces (23, 24/1, 24/2, 37) of the insulating body (17) in the liquid, soft or viscous state and after the joining of the involved longitudinal sections (17/1, 17/3, 17/5) of the insulating body (17) has been subjected, if appropriate, to an aftertreatment (polymerisation).
5. Spark plug according to Claim 4, characterized in that the annular electrical insulating elements (17/2, 17/4) consist of epoxy resin to which, if appropriate, fillers have been added in known manner to compensate the different thermal expansion behaviour of the involved longitudinal sections (17/1, 17/3, 17/5) of the insulating body (17).
6. Spark plug according to one of Claims 1 to 5, characterized in that the separating surfaces (23, 24/1, 24/2, 37) of the involved longitudinal sections (17/1, 17/3, 17/5) of the insulating body (17) have a peak-tovalley height (Rz) of less than 30 µm.
7. Spark plug according to Claim 6, characterized in that the separating surfaces (23, 24/1, 24/2, 37) of the involved longitudinal sections (17/1, 17/3, 17/5) of the insulating body (17) preferably have a peak-to-valley height (Rz) of less than 5 µm.
8. Spark plug according to one of Claims 1 to 7, characterized in that the separating surfaces (23, 24/1, 24/2, 37) of the insulating body (17) are provided with a glaze layer.
9. Spark plug according to one of Claims 1 to 8, characterized in that the annular gap between the central section (31/2) of the terminal stud (31) and the dielectric component (17/3) and/or the annular gap between the dielectric component (17/3) and the metal casing (11) is 0.01 to 0.50 mm wide and filled only with gas.
10. Spark plug according to Claim 9, characterized in that the annular gaps are 0.05 to 0.30 mm wide.
EP86902799A 1985-05-31 1986-05-10 Spark plug for internal combustion engines Expired EP0226595B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE3519513 1985-05-31
DE3519513 1985-05-31
DE3600511 1986-01-10
DE19863600511 DE3600511A1 (en) 1985-05-31 1986-01-10 SPARK PLUG FOR INTERNAL COMBUSTION ENGINES

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EP0226595A1 EP0226595A1 (en) 1987-07-01
EP0226595B1 true EP0226595B1 (en) 1989-12-06

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US (1) US4746834A (en)
EP (1) EP0226595B1 (en)
DE (2) DE3600511A1 (en)
ES (1) ES8707826A1 (en)
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US6559376B2 (en) 1996-09-30 2003-05-06 Nology Engineering, Inc. Combustion initiation device and method for tuning a combustion initiation device
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Also Published As

Publication number Publication date
DE3600511A1 (en) 1986-12-04
DE3667364D1 (en) 1990-01-11
EP0226595A1 (en) 1987-07-01
WO1986007207A1 (en) 1986-12-04
US4746834A (en) 1988-05-24
ES555553A0 (en) 1987-08-16
ES8707826A1 (en) 1987-08-16

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