EP1188023B1 - Electrically heatable glow plug or glow rod for combustion engines - Google Patents

Electrically heatable glow plug or glow rod for combustion engines Download PDF

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Publication number
EP1188023B1
EP1188023B1 EP00925294A EP00925294A EP1188023B1 EP 1188023 B1 EP1188023 B1 EP 1188023B1 EP 00925294 A EP00925294 A EP 00925294A EP 00925294 A EP00925294 A EP 00925294A EP 1188023 B1 EP1188023 B1 EP 1188023B1
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EP
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Prior art keywords
glow
glow plug
coil
plug
powder filling
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Expired - Lifetime
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EP00925294A
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German (de)
French (fr)
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EP1188023A1 (en
Inventor
Klaus Gessner
Roland Klak
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Mercedes Benz Group AG
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DaimlerChrysler AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines

Definitions

  • the invention is based on an electrically heatable glow plug or a glow rod for internal combustion engines according to the preamble of claim 1, as for example from EP 450 185 B1 as known.
  • No. 5,791,308 describes a glow plug in which a heating coil around a core of refractory material is wound. This core acts as a heat sink, thus absorbing the heat of the heating coil and increases their life.
  • glow plugs are used in the combustion chamber for preheating during a cold start or - as a glow rod in the intake duct - used for intake air preheating.
  • the glow plug or The glow rod consist of a corrosion-free metallic Sheath, a heating coil and a control coil and an electric insulating, compressed powder filling.
  • the heating and Control coil consists of a ferritic heating system Steel to which a pure nickel wire is welded as a resistance is.
  • the material of the heating coil is subject during operation a thermal and chemical influence affecting the life may affect the glow plug. At least put these influences are essential parameters regarding the lifetime the glow plug dar. Due to the high operating temperatures the heating coil and a still existing Oxygen supply in the compressed powder filling occurs to a gradual corrosion of the heating coil. And that is possible On the one hand, intercrystalline corrosion occurs by crystal growth and tendency to coarse grain formation ferritic heating conductors is promoted. On the other hand it can at high temperatures for corrosion on the free surface the heating coil and thus to weaken the Schudrahtqueriteses come.
  • magnesium oxide is generally used. Around the atmospheric oxygen contained in the pores of the powder filling minimize the powder is very highly compressed, by placing the filled metal shell from the outside through a concentric acting impact tool compressed and thereby im Diameter is reduced.
  • the powder filling is in the range the Schustabspitze particularly compacted by the there Metal shell is conically compressed.
  • the object of the invention is based on the generic Glow plug for a longer life of the heating coil to improve.
  • glow plugs in the combustion chamber for the Pre-heating during cold start or - as a rod-shaped flame glow plug or flame system in the supply air duct - for air preheating used.
  • the embodiment shown in Figure 1 a glow plug has a glow tube 5, the in held a plug body 1 and electrically conductive with him connected is.
  • the jacket of the glow tube is usually from a nickel-rich iron alloy or from a corrosion-free one Nickel-based alloy, such as Inconel 601 and is usually electrically connected as a ground, so negatively. This electrical ground connection comes over that Screw thread 7 and / or through the cone 7a at the bottom front end of the candle body 1 state.
  • the glow tube In the glow tube is a heating coil 8 with a via a Connection welding 11 control coil 9 welded thereto and an electrically insulating, compacted powder filling 10 arranged.
  • This powder filling has, in particular in condensed state, several functions: It provides first that the heating (8) and control coil 9 within, the glow tube stationary housed and fixed and are held electrically isolated.
  • the compact Powder By the compact Powder must as possible the heat generated in the heating coil 8 well forwarded to the mantle of the glow tube.
  • the compression of the powder Air pockets especially a certain residual oxygen be eliminated as possible. This requires a special make intensive compaction of the powder, especially in the Area of the heating coil 8.
  • the heating and control coil 8, 9 is in the heating area (Heating coil 8) made of a ferritic steel, e.g. from one Iron-chromium-aluminum alloy with 17 to 22% chromium and 3 up to 7% aluminum; is a commonly used alloy Kantal AF CrA1225. At such a heating coil is a coiled Wire (control coil 9) welded from pure nickel (Joint weld 11), the function of a variable resistor has.
  • the heating coil 8 is in the top of Glow tube via a sealing weld 12 with the glow tube connected.
  • the other end of the control coil 9 is one in one Insulating washer 4 embedded connecting bolt 2 connected, the electrically isolated and sealed by a seal 6 is led out of the candle body 1.
  • the connecting bolt is via a nut 3, which ensures a cable eye contacted with the connecting bolt, with the plus pole one Power source connected.
  • the connection pin 2 am upper open end of the glow tube with a soft insulating Gasket 6 'sealed, the penetration of Atmospheric oxygen in the compressed powder filling reliable should prevent.
  • magnesium oxide is generally used.
  • the filled glow tube from the outside through a concentrically acting impact tool radially compressed and thereby reduced in diameter, being also a conical History is achievable.
  • the powder filling is compressed very strongly, by the metal sheath compressed particularly strong radially becomes.
  • a diffusion treatment such as nitriding recommended, which by nitride formation in the diffusion zone leads to an increase in hardness and as a result of the diffusion processes a gradual transition from the hardened Edge zone to the soft core results.
  • This diffusion zone 13 of the coils 8, 9 expediently has a depth t from about 5 to 10 microns.
  • the helices Due to the hardening of the helices only in a near-surface boundary layer 13, the helices nevertheless nevertheless remain plastically deformable as a whole. On the other hand, a pronounced graining of the wire surface during the radial compression of the powder filling by the surface hardening is avoided. The helices have a smooth surface 14 even after the powder filling has been compressed. As a result, mechanical pre-damage of the conductor wire can be avoided. The result is a longer life expectancy of the conductor and thus the entire glow plug.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)

Description

Die Erfindung geht aus von einer elektrisch beheizbaren Glühkerze oder einem Glühstab für Verbrennungsmotoren nach dem Oberbegriff von Anspruch 1, wie sie beispielsweise aus der EP 450 185 B1 als bekannt hervorgeht.The invention is based on an electrically heatable glow plug or a glow rod for internal combustion engines according to the preamble of claim 1, as for example from EP 450 185 B1 as known.

In der US 5791 308 wird eine Glühkerze beschrieben, bei der eine Heizwendel um einen Kern aus einem refraktären Material gewickelt ist. Dieser Kern wirk als Wärmesenke, absorbiert somit die Wärme der Heizwendel und erhöht deren Lebensdauer.No. 5,791,308 describes a glow plug in which a heating coil around a core of refractory material is wound. This core acts as a heat sink, thus absorbing the heat of the heating coil and increases their life.

In Dieselmotoren werden Glühkerzen im Brennraum für die Vorheizung beim Kaltstart oder - als Glühstab im Ansaugkanal - für die Ansaugluftvorwärmung eingesetzt. Die Glühkerze oder der Glühstab bestehen aus einem korrosionsfreien metallischen Mantel, aus einer Heiz- und einer Regelwendel und aus einer elektrisch isolierenden, verdichteten Pulverfüllung. Die Heizund Regelwendel besteht im Heizbereich aus einem ferritischen Stahl, an die ein Reinnickeldraht als Regelwiderstand angeschweißt ist.In diesel engines, glow plugs are used in the combustion chamber for preheating during a cold start or - as a glow rod in the intake duct - used for intake air preheating. The glow plug or The glow rod consist of a corrosion-free metallic Sheath, a heating coil and a control coil and an electric insulating, compressed powder filling. The heating and Control coil consists of a ferritic heating system Steel to which a pure nickel wire is welded as a resistance is.

Der Werkstoff der Heizwendel unterliegt während des Betriebes einer thermischen und chemischen Beeinflussung, die die Lebensdauer der Glühkerze beeinträchtigen kann. Zumindest stellen diese Einflüsse wesentliche Parameter hinsichtlich der Lebensdauer der Glühkerze dar. Aufgrund der hohen Betriebstemperaturen der Heizwendel und eines nach wie vor noch vorhandenen Sauerstoffangebotes in der verdichteten Pulverfüllung kommt es zu einer schleichenden Korrosion der Heizwendel. Und zwar kann es zum einen zu einer interkristallinen Korrosion kommen, die durch Kristallwachstum und Neigung zur Grobkornbildung bei ferritischen Heizleitern gefördert wird. Zum anderen kann es bei hohen Temperaturen zur Korrosion an der freien Oberfläche der Heizwendel und somit zur Schwächung des Heizdrahtquerschnittes kommen.The material of the heating coil is subject during operation a thermal and chemical influence affecting the life may affect the glow plug. At least put These influences are essential parameters regarding the lifetime the glow plug dar. Due to the high operating temperatures the heating coil and a still existing Oxygen supply in the compressed powder filling occurs to a gradual corrosion of the heating coil. And that is possible On the one hand, intercrystalline corrosion occurs by crystal growth and tendency to coarse grain formation ferritic heating conductors is promoted. On the other hand it can at high temperatures for corrosion on the free surface the heating coil and thus to weaken the Heizdrahtquerschnittes come.

Als Pulverfüllung wird im allgemeinen Magnesiumoxid verwendet. Um den in den Poren der Pulverfüllung enthaltenen Luftsauerstoff zu minimieren, wird das Pulver sehr stark verdichtet, indem der gefüllte Metallmantel von außen durch ein konzentrisch wirkendes Schlagwerkzeug gestaucht und dadurch im Durchmesser reduziert wird. Die Pulverfüllung wird im Bereich der Heizstabspitze besonders stark verdichtet, indem dort der Metallmantel konisch gestaucht wird.As powder filling, magnesium oxide is generally used. Around the atmospheric oxygen contained in the pores of the powder filling minimize the powder is very highly compressed, by placing the filled metal shell from the outside through a concentric acting impact tool compressed and thereby im Diameter is reduced. The powder filling is in the range the Heizstabspitze particularly compacted by the there Metal shell is conically compressed.

Aufgabe der Erfindung ist es, die gattungsgemäß zugrundegelegte Glühkerze bezüglich einer höheren Lebensdauer der Heizwendel zu verbessern.The object of the invention is based on the generic Glow plug for a longer life of the heating coil to improve.

Diese Aufgabe wird - ausgehend von der gattungsgemäß zugrundegelegten Glühkerze - erfindungsgemäß durch die kennzeichnenden Merkmale von Anspruch 1 gelöst. Es hat sich nämlich herausgestellt, daß bei dem Verdichten der Pulverfüllung durch das radiale Stauchen des Mantelrohres auch der Draht der Heizwendel und der der Regelwendel mechanisch stark beansprucht und dabei unbeabsichtigt z.B. durch Kerben, Vertiefungen o.dgl. vorgeschädigt, d.h. lokal im Querschnitt verengt wird. Aufgrund der Härtezunahme der Wendel an ihrer Oberfläche, insbesondere durch Nitrieren, ist die Wendel in der Lage, die mechanische Beanspruchung beim Verdichten der Pulverfüllung ohne nennenswerte Vorschädigung zu überstehen.This task is - based on the generic underlying Glow plug - according to the invention by the characterizing Characteristics of claim 1 solved. It turns out that in the compression of the powder filling by the radial Compression of the jacket tube and the wire of the heating coil and the rule coil mechanically stressed and thereby inadvertently e.g. by notches, depressions or the like. been damaged, i.e. locally narrowed in cross section. Due to the Hardness increase of the helix on its surface, in particular by nitriding, the helix is capable of mechanical Stress when compacting the powder filling without appreciable To survive previous damage.

Zweckmäßige Ausgestaltungen der Erfindung können den Unteransprüchen entnommen werden; im übrigen ist die Erfindung anhand eines in der Zeichnung dargestellten Ausführungsbeispieles nachfolgend noch erläutert; dabei zeigen:

Fig. 1
einen Längsschnitt durch eine Glühkerze,
Fig. 2
eine vergrößerte Darstellung der Einzelheit II aus Figur 1 und
Fig. 3
einen Querschnitt durch eine herkömmliche Glühkerze im Bereich der Einzelheit II mit oberflächlichen Vorschädigungen der Wendel durch die mechanische Beanspruchung beim Verdichten der Pulverfüllung.
Advantageous embodiments of the invention can be taken from the subclaims; Moreover, the invention with reference to an embodiment shown in the drawing is explained below; show:
Fig. 1
a longitudinal section through a glow plug,
Fig. 2
an enlarged view of the detail II of Figure 1 and
Fig. 3
a cross section through a conventional glow plug in the range of detail II with superficial Vorschädigungen the helix by the mechanical stress during compression of the powder filling.

In Dieselmotoren werden Glühkerzen im Brennraum für die Vorheizung beim Kaltstart oder - als stabförmige Flammglühkerze oder Flammanlage im Zuluftkanal - für die Luftvorwärmung eingesetzt. Das in Figur 1 dargestellte Ausführungsbeispiel einer Glühkerze weist ein Glührohr 5 auf, das in einem Kerzenkörper 1 gehaltert und mit ihm elektrisch leitend verbunden ist. Der Mantel des Glührohres besteht meist aus einer nickelreichen Eisenlegierung oder aus einer korrosionsfreien Nickelbasislegierung wie z.B. Inconel 601 und ist elektrisch in der Regel als Massepol, also negativ geschaltet. Diese elektrische Masse-Verbindung kommt über das Einschraubgewinde 7 und/oder durch den Konus 7a am unteren strirnseitigen Ende des Kerzenkörpers 1 zustande.In diesel engines, glow plugs in the combustion chamber for the Pre-heating during cold start or - as a rod-shaped flame glow plug or flame system in the supply air duct - for air preheating used. The embodiment shown in Figure 1 a glow plug has a glow tube 5, the in held a plug body 1 and electrically conductive with him connected is. The jacket of the glow tube is usually from a nickel-rich iron alloy or from a corrosion-free one Nickel-based alloy, such as Inconel 601 and is usually electrically connected as a ground, so negatively. This electrical ground connection comes over that Screw thread 7 and / or through the cone 7a at the bottom front end of the candle body 1 state.

In dem Glührohr ist eine Heizwendel 8 mit einer über eine Verbindungsschweißüng 11 daran angeschweißten Regelwendel 9 und eine elektrisch isolierende, verdichtete Pulverfüllung 10 angeordnet. Diese Pulverfüllung hat, insbesondere in verdichtetem Zustand, mehrere Funktionen: Sie sorgt zunächst dafür, daß die Heiz- (8) und Regelwendel 9 innerhalb, des Glührohres ortsfest untergebracht und fixiert sowie elektrisch isoliert gehaltert sind. Durch das verdichte Pulver muß die in der Heizwendel 8 erzeugte Wärme möglichst gut an den Mantel des Glührohres weitergeleitet werde. Außerdem sollen durch die Komprimierung des Pulvers etwaige Lufteinschlüsse, insbesondere ein gewisser Restsauerstoff möglichst beseitigt werden. Dies erfordert macht eine besonders intensive Verdichtung des Pulvers, insbesondere im Bereich der Heizwendel 8.In the glow tube is a heating coil 8 with a via a Connection welding 11 control coil 9 welded thereto and an electrically insulating, compacted powder filling 10 arranged. This powder filling has, in particular in condensed state, several functions: It provides first that the heating (8) and control coil 9 within, the glow tube stationary housed and fixed and are held electrically isolated. By the compact Powder must as possible the heat generated in the heating coil 8 well forwarded to the mantle of the glow tube. In addition should be possible by the compression of the powder Air pockets, especially a certain residual oxygen be eliminated as possible. This requires a special make intensive compaction of the powder, especially in the Area of the heating coil 8.

Die Heiz- und Regelwendel 8, 9 besteht im Heizbereich (Heizwendel 8) aus einem ferritischen Stahl, z.B. aus einer Eisen-Chrom-Aluminium-Legierung mit 17 bis 22 % Chrom und 3 bis 7 % Aluminium; eine häufig verwendete Legierung ist Kantal AF CrA1225. An eine solche Heizwendel ist ein gewendelter Draht (Regelwendel 9) aus reinem Nickel angeschweißt (Verbindungsschweißung 11), der die Funktion eines Regelwiderstandes besitzt. Die Heizwendel 8 ist in der Spitze des Glührohres über eine Dichtschweißung 12 mit dem Glührohr verbunden.The heating and control coil 8, 9 is in the heating area (Heating coil 8) made of a ferritic steel, e.g. from one Iron-chromium-aluminum alloy with 17 to 22% chromium and 3 up to 7% aluminum; is a commonly used alloy Kantal AF CrA1225. At such a heating coil is a coiled Wire (control coil 9) welded from pure nickel (Joint weld 11), the function of a variable resistor has. The heating coil 8 is in the top of Glow tube via a sealing weld 12 with the glow tube connected.

Das andere Ende der Regelwendel 9 ist mit einem in einer Isolierscheibe 4 eingebetteten Anschlußbolzen 2 verbunden, der elektrisch isoliert und über eine Dichtung 6 abgedichtet aus dem Kerzenkörper 1 herausgeführt ist. Der Anschlußbolzen wird über eine Mutter 3, die eine Kabelöse sicher mit dem Anschlußbolzen kontaktiert, mit dem Pluspol einer Stromquelle verbunden. Außerdem ist der Anschlußbolzen 2 am oberen offenen Ende des Glührohres mit einer weichen isolierenden Dichtung 6' abgedichtet, die ein Eindringen von Luftsauerstoff in die komprimierte Pulverfüllung zuverlässig verhindern soll.The other end of the control coil 9 is one in one Insulating washer 4 embedded connecting bolt 2 connected, the electrically isolated and sealed by a seal 6 is led out of the candle body 1. The connecting bolt is via a nut 3, which ensures a cable eye contacted with the connecting bolt, with the plus pole one Power source connected. In addition, the connection pin 2 am upper open end of the glow tube with a soft insulating Gasket 6 'sealed, the penetration of Atmospheric oxygen in the compressed powder filling reliable should prevent.

Als Pulverfüllung 10 wird im allgemeinen Magnesiumoxid verwendet. Um die Pulverfüllung - wie beschrieben - zu verdichten, wird das gefüllte Glührohr von außen durch ein konzentrisch wirkendes Schlagwerkzeug radial gestaucht und dadurch im Durchmesser reduziert, wobei auch ein konischer Verlauf erreichbar ist. Vor allem im Bereich der Glührohrspitze wird die Pulverfüllung besonders stark verdichtet, indem dort der Metallmantel besonders stark radial gestaucht wird. As powder filling 10 magnesium oxide is generally used. To compact the powder filling - as described - is the filled glow tube from the outside through a concentrically acting impact tool radially compressed and thereby reduced in diameter, being also a conical History is achievable. Especially in the area of the glow tube tip the powder filling is compressed very strongly, by the metal sheath compressed particularly strong radially becomes.

Aufgrund der starken Verdichtung der Pulverfüllung wird die gesamte Wendel 8, 9, insbesondere aber die Heizwendel 8 mechanisch stark beansprucht. Bei der radialen Stauchung des Glührohres 5 wird nicht nur dessen Mantel plastisch verformt, sonder auch die eingelagerten Wendeln 8 und 9. Die verdichtende und verdichtete Pulverfüllung 10 überträgt Kraftwirkungen von den außen angreifenden Schlagwerkzeugen isostatisch auch auf die Windungen der Heiz- und Regelwendeln 8 bzw. 9 und reduzieren deren Durchmesser bei diesem Vorgang in entsprechendem Maße. Nachdem aber die Pulverfüllung nicht völlig homogen ist, sondern gewissen Ungleichmäßigkeiten unterliegt, sind die über die Pulverfüllung auf die Wendeln ausgeübten Kräfte entsprechend der Streuung der Pulverdichte lokal unterschiedlich groß.Due to the strong compression of the powder filling is the entire coil 8, 9, but in particular the heating coil 8 mechanically heavily used. At the radial compression of the Glow tube 5 is not only plastically deformed its shell, but also the embedded coils 8 and 9. The compacting and compacted powder filling 10 transmits Power effects of the externally attacking striking tools isostatic also on the windings of heating and control spirals 8 and 9 and reduce their diameter at this Operation to an appropriate extent. But after the powder filling not completely homogeneous, but certain irregularities are subject to, over the powder filling up The forces exerted by the helices correspond to the dispersion of the Powder density locally different sizes.

Bei unbehandelten Wendeln führt dies zu einer lokal unterschiedlichen plastischen Stauchung der Wendeln. Die unterschiedliche Stauchung ihrerseits ruft eine stochastisch genarbte Oberfläche der Wendeln 8' hervor, wie diese in Figur 3 am Beispiel einer herkömmlichen Ausführung einer Glühkerze mit unbehandelter Wendel 8' gezeigt ist. Diese Wendel weist bereits im Neuzustand nach der Pulververdichtung eine genarbte Oberfläche 15 auf. In dieser Oberflächennarbung ist nach den Erkenntnissen der Erfindung eine gewisse Vorschädigung zu erblicken. Es kann nämlich aufgrund einer solchen stochastischen Narbung zu lokalen Querschnittsverengungen des Leitungsquerschnittes der Wendel kommen. Diese lokale Querschnittsverengung wiederum führt zu einer lokalen Erhöhung des elektrischen Widerstandes und somit im Betrieb zu einer lokal stärkeren Erwärmung der Wendel. Das bedeutet, daß die thermischen und chemischen Alterungsprozesse an dieser Stelle aufgrund des höheren Temperaturniveaus schneller ablaufen als an anderen Stellen. Eine solche, anfänglich nur kleine, narbungsbedingte Verengung des Leitungsquerschnitts der Wendel kann somit lebensdauerbestimmend, also lebensdauerverkürzend sein. In untreated coils, this leads to a locally different plastic compression of the helices. The different ones Upset in turn gets a stochastically grained Surface of the coils 8 ', as shown in FIG 3 using the example of a conventional embodiment of a glow plug with untreated coil 8 'is shown. This helix already has a new state after the powder compaction one grained surface 15 on. In this surface graining is according to the findings of the invention, a certain amount of damage to behold. It can namely because of a such stochastic graining to local cross-sectional constrictions of the wire cross section of the helix come. This local cross-sectional narrowing in turn leads to a local increase in electrical resistance and thus in the Operation for a locally stronger heating of the coil. The means that the thermal and chemical aging processes at this point due to the higher temperature level run faster than elsewhere. Such, Initially, only small, scarred by scarring of the The wire cross-section of the helix can thus be lifetime-specific, So shorten the life.

Erfindungsgemäß soll die Lebensdauer der Wendeln, insbesondere die beim Verdichten besonders stark mechanisch beanspruchte Heizwendel 8, die im Betrieb auch thermisch besonders stark beansprucht ist, erhöht werden. Zur Lebensdauererhöhung werden erfindungsgemäß die elektrisch leitenden Wendeln 8, 9, zumindest aber die besonders gefährdete Heizwendel 8, an der Oberfläche gehärtet. Und zwar wird vorteilhafter Weise eine Diffusionsbehandlung wie Nitrieren empfohlen, welche durch Nitridbildung in der Diffusionszone zu einer Steigerung der Härte führt und infolge der Diffusionsvorgänge einen allmählichen Übergang von der gehärteten Randzone zum weichen Kern ergibt. Diese Diffusionszone 13 der Wendeln 8, 9 weist zweckmäßiger Weise eine Tiefe t von etwa 5 bis 10 µm auf.According to the invention, the life of the coils, in particular the particularly mechanically stressed during compression Heating coil 8, which is also thermally especially in operation heavily loaded. To increase lifespan According to the invention, the electrically conductive Spireln 8, 9, but at least the most vulnerable heating coil 8, hardened on the surface. And that will be more advantageous Do a diffusion treatment such as nitriding recommended, which by nitride formation in the diffusion zone leads to an increase in hardness and as a result of the diffusion processes a gradual transition from the hardened Edge zone to the soft core results. This diffusion zone 13 of the coils 8, 9 expediently has a depth t from about 5 to 10 microns.

Aufgrund der Härtung der Wendeln lediglich in einer oberflächennahen Randschicht 13 bleiben die Wendeln gleichwohl als ganzes plastisch verformbar. Andererseits wird eine ausgeprägte Narbung der Drahtoberfläche beim radialen Verdichten der Pulverfüllung durch die Randschichthärtung vermieden. Die Wendeln weisen auch nach dem Verdichten der Pulverfüllung eine glatte Oberfläche 14 auf. Dadurch werden mechanische Vorschädigungen des Leiterdrahtes vermieden.
   Die folge ist eine höhere Lebensdauererwartung des Leiters und somit der gesamten Glühkerze.Due to the hardening of the helices only in a near-surface boundary layer 13, the helices nevertheless nevertheless remain plastically deformable as a whole. On the other hand, a pronounced graining of the wire surface during the radial compression of the powder filling by the surface hardening is avoided. The helices have a smooth surface 14 even after the powder filling has been compressed. As a result, mechanical pre-damage of the conductor wire can be avoided.
The result is a longer life expectancy of the conductor and thus the entire glow plug.

Claims (4)

  1. Electrically heated glow plug or glow rod for internal combustion engines, with a corrosion-resistant heat pipe closed at the end which undertakes filling from an electrically non-conductive compacted powder, in which an electrically conductive coil is embedded
    characterised in that
    at least the heating coil (8) is hardened on its upper surface.
  2. Glow plug or glow rod according to claim 1
    characterised in that
    the electrically conductive coil (8, 9) is hardened on its upper surface.
  3. Glow plug or glow rod according to claim 1
    characterised in that
    the electrically conductive coil (8, 9) is hardened at least on a part of its longitudinal expanse on its upper surface by a diffusion treatment, in particular by nitration.
  4. Glow plug or glow rod according to claim 3
    characterised in that
    the hard diffusion zone (13) of the electrically conductive coil (8, 9) has a depth (t) of approximately 5 to 10 µm.
EP00925294A 1999-06-18 2000-05-19 Electrically heatable glow plug or glow rod for combustion engines Expired - Lifetime EP1188023B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE1999128037 DE19928037C1 (en) 1999-06-18 1999-06-18 Electrically heated glow plug/rod for combustion engine has corrosion-resistant glow tube closed at ends with electrically conducting, compressed powder filling containing embedded coil
DE19928037 1999-06-18
PCT/EP2000/004521 WO2000079185A1 (en) 1999-06-18 2000-05-19 Electrically heatable glow plug or glow rod for combustion engines

Publications (2)

Publication Number Publication Date
EP1188023A1 EP1188023A1 (en) 2002-03-20
EP1188023B1 true EP1188023B1 (en) 2004-06-23

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EP (1) EP1188023B1 (en)
JP (1) JP3618092B2 (en)
DE (1) DE19928037C1 (en)
WO (1) WO2000079185A1 (en)

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JP4971837B2 (en) * 2006-04-03 2012-07-11 日本特殊陶業株式会社 Glow plug and glow plug mounting structure.
JP5276425B2 (en) * 2008-12-15 2013-08-28 日本特殊陶業株式会社 Sheath heater and glow plug
US11317761B2 (en) * 2013-05-02 2022-05-03 Original Pellet Grill Company Llc Double-sealed high-temperature resistant DC ignitor for use with wood pellet burner assemblies
JP6392000B2 (en) * 2014-06-17 2018-09-19 日本特殊陶業株式会社 Glow plug
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CN111537344B (en) * 2020-05-11 2022-03-08 西南石油大学 Method for testing compressive strength of rigid plugging material

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WO2000079185A1 (en) 2000-12-28
DE19928037C1 (en) 2000-05-25
EP1188023A1 (en) 2002-03-20
JP2003502613A (en) 2003-01-21
JP3618092B2 (en) 2005-02-09

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