EP1944551B1 - Manufacturing process for a glow plug - Google Patents

Manufacturing process for a glow plug Download PDF

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Publication number
EP1944551B1
EP1944551B1 EP07122574A EP07122574A EP1944551B1 EP 1944551 B1 EP1944551 B1 EP 1944551B1 EP 07122574 A EP07122574 A EP 07122574A EP 07122574 A EP07122574 A EP 07122574A EP 1944551 B1 EP1944551 B1 EP 1944551B1
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EP
European Patent Office
Prior art keywords
heating coil
heater coil
coil
glow
glow tube
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.)
Not-in-force
Application number
EP07122574A
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German (de)
French (fr)
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EP1944551A1 (en
Inventor
Armin Kussmaul
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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Publication of EP1944551A1 publication Critical patent/EP1944551A1/en
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Publication of EP1944551B1 publication Critical patent/EP1944551B1/en
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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
    • 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
    • F23Q2007/004—Manufacturing or assembling methods

Definitions

  • the invention relates to a method for producing the glow plug according to the preamble of claim 1.
  • WO 03/038340 A1 is an electrically heatable glow plug and a method for producing an electrically heated glow plug known.
  • an electrically heatable glow plug for internal combustion engines is produced in which an electrically conductive heating coil, which is at least partially made of aluminum, in particular of an aluminum-iron-chromium alloy, is introduced into a closed end glow tube.
  • oxygen donors are introduced into the glow tube to form an aluminum oxide layer on the surface of the heating coil before or during the heating of the heating coil.
  • a first insulating powder is introduced into the glow tube, which comprises a material acting as oxygen donor material.
  • the heating coil is embedded as completely as possible in this first insulating powder.
  • a glow plug is installed in the combustion chamber of air-compressing internal combustion engines and has a tubular metallic candle housing. In the plug housing a longitudinal bore is embedded, in which a glow plug is inserted with a part of its length sealing. Further, a serving for power supply, partially lying in the glow plug connecting bolt is provided in which a glow pencil tip facing, axially extending recess is formed in the connected by a male / Stemmitati between the connecting bolt and the centering of the filament. In the glow pin tip facing the end of the connecting bolt is an elongated, extending in the axial direction of the connecting bolt and open to one side Recess or bead. Their clear width corresponds to the circumference of the connecting bolt about the diameter of the centering turns of the filament.
  • the glow plug comprises a plug housing and a connected to the plug housing connecting device for the glow current, coupled to the connecting device glow tube, which is closed on its side facing away from the plug housing. Furthermore, the glow plug comprises an incandescent tube, on which at a connection pin coupled to the connection device a wire coil-shaped resistance element is arranged, wherein the resistance element consists of a heating coil and a control coil.
  • the control coil has a resistance between 20 and 100 m ⁇ .
  • DE 101 57 466 A1 is an electrically heatable glow plug and a method for producing an electrically heated glow plug known.
  • an electrically heatable glow plug for internal combustion engines is produced in which an electrically conductive heating coil, which is at least partially made of aluminum, in particular of an aluminum-iron-chromium alloy, is introduced into a closed end glow tube.
  • oxygen donors are introduced into the glow tube to form an aluminum oxide layer on the surface of the heating coil before or during the heating of the heating coil.
  • a first insulating powder is introduced into the glow tube, which comprises a material acting as oxygen donor material. The heating coil is embedded as completely as possible in this first insulating powder.
  • the glow plug used according to this solution comprises a metallic glow tube made of a heating coil with a control coil arranged thereon and an electrically insulating powder filling compressed within the glow tube. The powder filling ensures that the heating coil is fixed and fixed inside the glow tube.
  • FR-A-2 579 116 describes a coating process to build a protective layer on the surface of a glow tube, which protects against corrosion and erosion.
  • the upper end of the lateral surface is precoated with graphite powder and a binder.
  • the outer surface of the glow plug is introduced full length into a reaction line where, depending on the coating, different reaction mixtures are applied via microwave induction heating. After this treatment, the coating of the graphite precoated part is removed and thus a coating is provided only in the front region of the lateral surface.
  • the glow tube is usually connected negative as a ground pole.
  • the filament is welded on the Schuleiterseite with the tip of the glow tube.
  • the other end of the filament is connected to a terminal bolt which is electrically isolated and sealed out of the socket of the glow plug and connected to the positive pole of the power source.
  • the connecting pin of the inner pole at the upper open end of the glow tube is sealed with a soft, insulating Viton seal, which reliably seals against the ingress of air.
  • the filament consists in the heating (heating coil) of a ferritic steel, z. B. of an iron-chromium-aluminum alloy. At such a trained heating coil is another Spiral made of pure nickel or a CO-Fe alloy welded, which takes over the function of a PTC resistor.
  • Nitrogen unlike oxygen, which forms a protective alumina layer on the surface of the heating coil, results in the formation of aluminum nitride inside the coil.
  • the formation of Aluminiumiunmitrid inside the coil has a local increase in electrical resistance and thus an early failure of the heating coil of the glow plug result.
  • chemical reactions with powder impurities may occur on the metallic surface of the heating coil at higher temperatures, which may be contained in the insulating powder, which may likewise lead to premature damage to the heating coil and failure of the annealing function.
  • the heating coil of the glow plug prior to the intended use of the glow plug of a thermal treatment, such that on the surface of the heating coil, a coating is formed as a protective layer.
  • the coating is an oxide layer which is formed by oxidation of an alloy constituent of the material of the heating coil due to the thermal treatment of the heating coil.
  • the coating by means of pre-oxidation takes place at a relatively high oxygen pressure, for. B. in a pure oxygen atmosphere or in air.
  • a particularly effective Protective layer by pre-oxidation is achieved when using an alloyed aluminum material of the heating coil, wherein the aluminum component of the material of the heating coil by the thermal treatment of the heating coil on the surface of the heating coil forms an ⁇ -Al 2 O 3 layer. Once formed on the surface of the heating coil, the ⁇ -Al 2 O 3 layer, the material of the heating coil is effectively protected, so that chemical reactions are prevented.
  • the ⁇ -Al 2 O 3 layer causes an increase in the life of the glow plug by its protective function.
  • Damaging chemical reactions can be caused, for example, by the formation of aluminum nitride in the interior of the helical material or by chemical reaction of foreign chemical constituents of the magnesium oxide. These chemical reactions are associated with the disadvantage that they cause an initial damage to the material of the heating coil and thus have the most adverse effect on the operating time of the glow plug.
  • the filament used as a heating coil is clamped in a suitable receptacle and preferably pulled apart easily.
  • a suitable receptacle By taking place in a horizontal or vertical plane pulling apart of the individual turns of the heating coil prevents the individual turns are in contact with each other.
  • the Schuetzlteil ie, the part of the helical material, which is received in the glow tube at the combustion chamber end, selectively, under application of an external stress between 1000 ° C and 1300 ° C in a period of 30 s to 15 minutes are annealed.
  • the heating coil can be annealed at a temperature of 1200 ° C for 10 min.
  • the heating coil After making the glow of the heating coil or the Schutschlabsacrificinges the heating coil is installed as usual in the glow plug.
  • the heating coil can be passively annealed after being connected to a connecting bolt and after being introduced into the glow tube by an induction coil enclosing the glow tube on the outer circumferential surface. Also in passive annealing, make sure that the outside induction coil only covers the front part of the helix material, i. detects the heating coil, and not the control coil, which should not be exposed to this heat treatment.
  • FIG. 1 shows that a glow plug 10 comprises a housing 12, in which a connecting bolt 14 is inserted.
  • the connecting bolt 14 is connected via a circular connector 18 or a differently designed screw or clamp connection with a positive pole of a current or voltage source.
  • Below the circular connector 18 is an insulating disc 20 for insulating the housing 14 against the circular connector 18.
  • Below the insulating washer 20 is a housing seal 16.
  • About the housing seal 16 is a cavity within the housing 12, in which the connecting bolt 14 is received against the environment sealed.
  • a radiator seal 22 which may be formed, for example, as a Viton seal. With this radiator seal 22 of the connecting bolt 14 is fixed on the one hand in the housing 12 and on the other hand sealed against a glow tube 24.
  • the glow tube 24 is made thin-walled, with its wall 26 enclosing a cavity and the wall 26 is the heat-emitting lateral surface 28.
  • a control coil 30 and a heating coil 32 are connected to each other at a joint 40 cohesively.
  • the cavity within the glow tube 24 is filled with an insulating material 34, which is preferably magnesium oxide.
  • the control coil 30 is connected to a connection below the connecting bolt 14, see reference numeral 38.
  • Reference numeral 36 denotes the joint of the heating coil 32 with the tip of the glow tube 24.
  • FIG. 3 can be in a schematic manner an arrangement for carrying out the invention proposed treatment of the heating coil of the glow plug according to FIG. 1 remove.
  • FIG. 2 shows a not belonging to the invention device for receiving the unconverted heating coil 32 having a first receiving part 52 and a second receiving part 54. Both the first receiving part 52 and the second receiving part 54 are connected to a support plate 58 including at least one electrical insulation 60. Both the first receiving part 52 and the second receiving part 54 include means for applying a horizontal bias.
  • the first receiving part 52 and the second receiving part 54 may each be provided with threaded portions through which bolt body 68 - as in FIG. 2 indicated - in the horizontal direction of pull, see arrow 62, can be pulled apart. Between the facing end faces of the clamping bolt 68, a heating coil 32 is clamped.
  • the ends of individual turns 55 of the heating coil 32 are connected to the mutually facing end faces of the two clamping bolts 68. Furthermore, the two clamping bolts 68 can be brought via connecting cable 66 with a voltage source 50 in connection.
  • an axially acting force through which the individual turns 55 of the heating coil 32 are pulled apart in the horizontal direction of pull 62. Accordingly, the individual turns 55 of the heating coil 32 in the horizontal direction stretched until the material of the individual turns 55 is brought into a distance 64, that is, the individual turns 55 of the heating coil 32 no longer contact each other.
  • the entire surface of the heating coil 32 is now exposed to an oxygen atmosphere or the air.
  • the oxygen contained in the air reacts with the surface of the heating coil 32, such that an ⁇ -Al 2 O 3 coating is formed thereon, in particular on the entire circumference of the individual turns 55.
  • This ⁇ -Al 2 O 3 coating is characterized by a cubic lattice structure.
  • the nitrogen in the air reacts much more slowly with the surface of the heating coil 32. Due to the faster reaction of oxygen in the air containing the ⁇ -Al 2 O 3 coating forms much faster, so that the surface of the heating coil 32 against a chemical reaction with the nitrogen contained in the air is very quickly protected.
  • the heating coil 32 in the in FIG. 2 schematically indicated device can be produced on the entire surface of the material of the heating coil 32, an ⁇ -Al 2 O 3 coating.
  • the two clamping bolts 68 can be energized directly via the voltage source 50 and the connecting cable 66.
  • the annealing of the heating coil 32 takes place during a period of time which is between 30 s and 5 min. During this period, a temperature in the temperature range between 1000 ° C and 1300 ° C is generated in the heating coil 32.
  • this treatment is to treat only the heating coil 32 and not the in FIG. 1 shown, extending between the terminal bolt 14 and the heating coil 32 extending, designated by reference numeral 30 control coil.
  • the heating coil 32 By pulling apart, ie stretching the heating coil 32 in the in FIG. 2 schematically indicated device, it can be achieved that the entire surface of the substantially wirelike material of the heating coil 32 of the air or an oxygen atmosphere is formed, can be exposed, so that a uniform formation of the ⁇ -Al 2 O 3 coating on the surface the material of the heating coil 32 takes place.
  • the heating coil 32 is protected by the pre-oxidation against chemical reactions that may occur, for example, that in the insulating material 34, in which the heating coil 32 and the control coil 30 are embedded, impurities may be present that lead to chemical reactions. Due to the ⁇ -Al 2 O 3 coating produced before assembly of the heating coil 32 in the glow tube 24, the material is protected against such chemical reactions, so that the life of a glow plug 10 produced in this way can be significantly extended.
  • the treatment of the surface of the material of the heating coil 32 is performed in an oxygen-enriched atmosphere, for example.
  • the representation according to FIG. 3 is to take a passive preheating of the heating coil according to the invention of a glow plug. This embodiment can be integrated particularly advantageous in the manufacturing process of the glow plug.
  • the heating coil 32 connected to the control coil 30, in the insulating material 34, which is accommodated in the glow tube 24, is embedded.
  • the control coil 30 and the heating coil 32 are electrically connected to the connecting bolt 14.
  • the control coil 30 is in electrical contact with the heating coil 32, since both are connected to one another at the joint 40.
  • the heating coil 32 in the illustration according to FIG. 3 connected to a tip 72 of the glow tube 24.
  • the glow tube 24 includes the wall 26, the thin-walled is formed to allow a better heat transfer.
  • the lateral surface 28 of the glow tube 24 is enclosed by an induction coil 70.
  • the induction coil 70 comprises a number of turns, which enclose the lateral surface 28 of the glow tube 24 only in the region in the interior of which the heating coil 32 is accommodated. Accordingly, the control coil 30, which is electrically contacted with the heating coil 32 and the terminal bolt 14, not surrounded by the turns of the induction coil 70.
  • the induction coil 70 is analogous to the representation according to FIG FIG. 2 with a voltage or current source 50 over in FIG. 3 also not shown connecting cable connected.
  • the induction coil 70 is connected to the voltage source 50, the circuit is closed, then a passive annealing of the heating coil 32, which is received in this state mounted in the glow tube 24.
  • passive annealing of the heating coil 32 its heating takes place at temperatures of 1000 ° C. to 1200 ° C. for a period of 3 min to 15 min, preferably at 1200 ° C. for about 10 min.
  • Even with the passive annealing in the installed in the glow tube 24 state of the heating coil 32 is at least during the thermal treatment of the heating coil 32, a stretching of the heating coil 32.
  • the connecting bolt 14 is pulled in the vertical direction from the glow tube 24 by an amount by suitable means in that the turns of the heating coil 32 are spaced apart from each other, as associated with FIG. 2 has been described. This ensures that the coating can be formed on the entire surface of the heating coil 32.
  • a pre-oxidation of the heating coil 32 of the glow plug 10 can be achieved.
  • the pre-oxidation prevents chemical reactions of the bare metallic material of the heating coil 32 when it is embedded in the insulating material 34, since this can be contaminated.
  • the ⁇ -Al 2 O 3 layer on the surface of the turns 55 of the heating coil 32 provides an increase in the life of the glow plug 10, since this coating performs a protective function and prevents chemical reactions with the base material of the heating coil 32 come about.

Description

Stand der TechnikState of the art

Die Erfindung betrifft ein Verfahren zur Herstellung der Glühstiftkerze nach dem Oberbegriff des Anspruchs 1.The invention relates to a method for producing the glow plug according to the preamble of claim 1.

Aus WO 03/038340 A1 ist eine elektrisch beheizbare Glühkerze und ein Verfahren zur Herstellung einer elektrisch beheizbaren Glühkerze bekannt. Gemäß des aus WO 03/038340 A1 bekannten Verfahrens wird eine elektrisch beheizbare Glühkerze für Verbrennungskraftmaschinen hergestellt, bei dem eine elektrisch leitfähige Heizwendel, die zumindest teilweise aus Aluminium gefertigt wird, insbesondere aus einer Aluminium-Eisen-Chrom-Legierung, in ein endseitig geschlossenes Glührohr eingebracht wird. Vor dem Betrieb der Glühkerze werden in das Glührohr Sauerstoffdonatoren eingebracht, um vor oder bei der Beheizung der Heizwendel eine Aluminiumoxidschicht an der Oberfläche der Heizwendel zu bilden. Nach dem Einbringen der Heizwendel in den Bereich der Spitze des Glührohrs wird ein erstes Isolierpulver in das Glührohr eingefüllt, welches ein als Sauerstoffdonator wirkendes Material umfasst. Die Heizwendel ist möglichst vollständig in dieses erste Isolierpulver eingebettet.Out WO 03/038340 A1 is an electrically heatable glow plug and a method for producing an electrically heated glow plug known. According to the WO 03/038340 A1 known method, an electrically heatable glow plug for internal combustion engines is produced in which an electrically conductive heating coil, which is at least partially made of aluminum, in particular of an aluminum-iron-chromium alloy, is introduced into a closed end glow tube. Before operating the glow plug, oxygen donors are introduced into the glow tube to form an aluminum oxide layer on the surface of the heating coil before or during the heating of the heating coil. After the introduction of the heating coil in the region of the tip of the glow tube, a first insulating powder is introduced into the glow tube, which comprises a material acting as oxygen donor material. The heating coil is embedded as completely as possible in this first insulating powder.

Aus DE 197 55 822 A1 ist eine Glühstiftkerze bekannt. Die Glühstiftkerze wird im Brennraum luftverdichtender Brennkraftmaschinen eingebaut und weist ein rohrförmiges metallisches Kerzengehäuse auf. In das Kerzengehäuse ist eine Längsbohrung eingelassen, in der ein Glühstift mit einem Teil seiner Länge abdichtend eingesetzt ist. Ferner ist ein zur Stromzuführung dienender, teilweise im Glühstift liegender Anschlussbolzen vorgesehen, in dem eine der Glühstiftspitze zugewandte, axial verlaufende Ausnehmung ausgebildet ist, in der durch eine Steck/Stemmverbindung zwischen dem Anschlussbolzen und den Zentrierwindungen der Glühwendel eine Verbindung hergestellt ist. In dem der Glühstiftspitze zugewandten Ende des Anschlussbolzens befindet sich eine längliche, in Achsrichtung des Anschlussbolzens verlaufende und nach einer Seite offene Ausnehmung beziehungsweise Sicke. Deren lichte Weite entspricht am Umfang des Anschlussbolzens etwa der des Durchmessers der Zentrierwindungen der Glühwendel.Out DE 197 55 822 A1 is known a glow plug. The glow plug is installed in the combustion chamber of air-compressing internal combustion engines and has a tubular metallic candle housing. In the plug housing a longitudinal bore is embedded, in which a glow plug is inserted with a part of its length sealing. Further, a serving for power supply, partially lying in the glow plug connecting bolt is provided in which a glow pencil tip facing, axially extending recess is formed in the connected by a male / Stemmverbindung between the connecting bolt and the centering of the filament. In the glow pin tip facing the end of the connecting bolt is an elongated, extending in the axial direction of the connecting bolt and open to one side Recess or bead. Their clear width corresponds to the circumference of the connecting bolt about the diameter of the centering turns of the filament.

Aus DE 102 48 802 A1 ist eine Glühstiftkerze mit stark verkürzter Regelwendel bekannt. Die Glühstiftkerze umfasst ein Kerzengehäuse und eine an dem Kerzengehäuse angeschlossene Anschlussvorrichtung für den Glühstrom, einem mit der Anschlussvorrichtung gekoppelten Glührohr, welches an seiner dem Kerzengehäuse abgewandten Seite verschlossen ist. Des Weiteren umfasst die Glühstiftkerze ein Glührohr, an dem an einem mit der Anschlussvorrichtung gekoppelten Anschlussbolzen ein drahtwendelförmiges Widerstandselement angeordnet ist, wobei das Widerstandselement aus einer Heizwendel und einer Regelwendel besteht. Die Regelwendel umfasst einen Widerstand zwischen 20 und 100 mΩ.Out DE 102 48 802 A1 is a glow plug with a greatly reduced control coil known. The glow plug comprises a plug housing and a connected to the plug housing connecting device for the glow current, coupled to the connecting device glow tube, which is closed on its side facing away from the plug housing. Furthermore, the glow plug comprises an incandescent tube, on which at a connection pin coupled to the connection device a wire coil-shaped resistance element is arranged, wherein the resistance element consists of a heating coil and a control coil. The control coil has a resistance between 20 and 100 mΩ.

Aus DE 101 57 466 A1 ist eine elektrisch beheizbare Glühkerze und ein Verfahren zur Herstellung einer elektrisch beheizbaren Glühkerze bekannt. Gemäß des aus DE 101 57 466 A1 bekannten Verfahrens wird eine elektrisch beheizbare Glühkerze für Verbrennungskraftmaschinen hergestellt, bei dem eine elektrisch leitfähige Heizwendel, die zumindest teilweise aus Aluminium gefertigt wird, insbesondere aus einer Aluminium-Eisen-Chrom-Legierung, in ein endseitig geschlossenes Glührohr eingebracht wird. Vor dem Betrieb der Glühkerze werden in das Glührohr Sauerstoffdonatoren eingebracht, um vor oder bei der Beheizung der Heizwendel eine Aluminiumoxidschicht an der Oberfläche der Heizwendel zu bilden. Nach dem Einbringen der Heizwendel in den Bereich der Spitze des Glührohrs wird ein erstes Isolierpulver in das Glührohr eingefüllt, welches ein als Sauerstoffdonator wirkendes Material umfasst. Die Heizwendel ist möglichst vollständig in dieses erste Isolierpulver eingebettet.Out DE 101 57 466 A1 is an electrically heatable glow plug and a method for producing an electrically heated glow plug known. According to the DE 101 57 466 A1 known method, an electrically heatable glow plug for internal combustion engines is produced in which an electrically conductive heating coil, which is at least partially made of aluminum, in particular of an aluminum-iron-chromium alloy, is introduced into a closed end glow tube. Before operating the glow plug, oxygen donors are introduced into the glow tube to form an aluminum oxide layer on the surface of the heating coil before or during the heating of the heating coil. After the introduction of the heating coil in the region of the tip of the glow tube, a first insulating powder is introduced into the glow tube, which comprises a material acting as oxygen donor material. The heating coil is embedded as completely as possible in this first insulating powder.

Bei den aus DE 197 55 822 A1 , DE 102 48 802 A1 und DE 101 57 466 A1 bekannten Glühstiftkerzen sind Glühstifte teilweise von einem rohrförmigen Kerzengehäuse umschlossen. Der gemäß dieser Lösung jeweils eingesetzte Glühstift umfasst ein metallisches Glührohr aus einer Heizwendel mit einer daran angeordneten Regelwendel sowie eine elektrisch isolierende, innerhalb des Glührohrs verdichtete Pulverfüllung. Die Pulverfüllung sorgt dafür, dass die Heizwendel im Inneren des Glührohrs ortsfest untergebracht und fixiert ist.At the DE 197 55 822 A1 . DE 102 48 802 A1 and DE 101 57 466 A1 known glow plugs glow plugs are partially enclosed by a tubular plug housing. The glow plug used according to this solution comprises a metallic glow tube made of a heating coil with a control coil arranged thereon and an electrically insulating powder filling compressed within the glow tube. The powder filling ensures that the heating coil is fixed and fixed inside the glow tube.

FR-A-2 579 116 beschreibt ein Beschichtungsverfahren um eine Schutzschicht an der Mantelfläche eines Glührohrs aufzubauen, die vor Korrosion und Erosion schützt. Hier wird das obere Ende der Mantelfläche mit Graphitpuder und einem Bindemittel vorbeschichtet. Die Mantelfläche der Glühkerze wird der vollen Länge nach in eine Reaktionsleitung eingebracht, wo je nach Beschichtung verschiedene Reaktionsgemische via Mikrowellen-Induktionsheizung aufgebracht werden. Nach dieser Behandlung wird die Beschichtung des mit Grafit vorbeschichteten Teils entfernt und somit ist eine Beschichtung nur im vorderen Bereich der Mantelfläche vorgesehen. FR-A-2 579 116 describes a coating process to build a protective layer on the surface of a glow tube, which protects against corrosion and erosion. Here, the upper end of the lateral surface is precoated with graphite powder and a binder. The outer surface of the glow plug is introduced full length into a reaction line where, depending on the coating, different reaction mixtures are applied via microwave induction heating. After this treatment, the coating of the graphite precoated part is removed and thus a coating is provided only in the front region of the lateral surface.

Aus DE 10 2005 024622 A1 ist eine Stabglühkerze mit einem Halter und einem darin angeordneten Heizstab mit Metallglührohr, das glühseitig vom Halter vorsteht. Zur Verlängerung der Lebensdauer ist das Metallglührohr an seinem vom Halter vorstehenden Teil wenigstens teilweise mit einer Beschichtung aus einem hochtemperaturfesten Material, beispielsweise aus einer Glasurpaste versehen.Out DE 10 2005 024622 A1 is a stick glow plug with a holder and a heating rod arranged therein with Metallglührohr projecting glow side of the holder. To extend the life of the metal glow tube is provided at its part projecting from the holder at least partially with a coating of a high temperature resistant material, such as a glaze paste.

Das Glührohr ist in der Regel als Massepol negativ geschaltet. Die Glühwendel ist auf der Heizleiterseite mit der Spitze des Glührohrs verschweißt. Das andere Ende der Glühwendel ist mit einem Anschlussbolzen verbunden, der elektrisch isoliert und abgedichtet aus dem Sockel der Glühkerze herausgeführt wird und mit dem Pluspol der Stromquelle verbunden wird. Zusätzlich ist der Anschlussbolzen des Innenpols am oberen offenen Ende des Glührohrs mit einer weichen, isolierenden Vitondichtung abgedichtet, die gegen Eindringen von Luft zuverlässig abdichtet. Die Glühwendel besteht im Heizbereich (Heizwendel) aus einem ferritischen Stahl, z. B. aus einer Eisen-Chrom-Aluminium-Legierung. An eine derart ausgebildete Heizwendel ist eine weitere Wendel aus reinem Nickel oder einer CO-Fe-Legierung angeschweißt, welche die Funktion eines PTC-Regelwiderstandes übernimmt.The glow tube is usually connected negative as a ground pole. The filament is welded on the Heizleiterseite with the tip of the glow tube. The other end of the filament is connected to a terminal bolt which is electrically isolated and sealed out of the socket of the glow plug and connected to the positive pole of the power source. In addition, the connecting pin of the inner pole at the upper open end of the glow tube is sealed with a soft, insulating Viton seal, which reliably seals against the ingress of air. The filament consists in the heating (heating coil) of a ferritic steel, z. B. of an iron-chromium-aluminum alloy. At such a trained heating coil is another Spiral made of pure nickel or a CO-Fe alloy welded, which takes over the function of a PTC resistor.

Als Pulverfüllung zur Fixierung der Wendel innerhalb des Glührohrs wird in der Regel Magnesiumoxid eingesetzt. Die Heizleiterlegierung schützt sich bei Glühen an der Luft innerhalb kürzester Zeit durch die Ausbildung einer dünnen α-Al2O3-Schicht gegen weitere Korrosion. Diese Voraussetzung ist jedoch bei Glühstiftkerzen aufgrund eines anfänglichen Sauerstoffmangels im eingebetteten Zustand der Heizwendel im Isolierpulver nicht gegeben. Während der zyklischen thermischen Beanspruchung während des Einsatzes "atmet" der Glühstift jedoch. Dadurch können geringe Mengen Luft in das Innere des Glühstiftes, d. h. des Hohlraumes, der an sich durch die Vitondichtung abgedichtet sein sollte, eindringen, so dass es zur gleichzeitigen Reaktion des Heizwendelmaterials mit Sauerstoff und Stickstoff kommt. Stickstoff führt im Gegensatz zu Sauerstoff, der an der Oberfläche der Heizwendel eine schützende Aluminiumoxid-Schicht bildet, zur Bildung von Aluminiumnitrid im Inneren der Wendel. Die Bildung von Aluminiunmitrid im Inneren der Wendel hat einen lokalen Anstieg des elektrischen Widerstandes und damit ein frühzeitiges Versagen der Heizwendel der Glühstiftkerze zur Folge. Außerdem kann es an der metallischen Oberfläche der Heizwendel bei höheren Temperaturen zu chemischen Reaktionen mit Pulververunreinigungen kommen, die im Isolierpulver enthalten sein können, die gleichfalls zu einer frühzeitigen Schädigung der Heizwendel und zum Versagen der Glühfunktion führen können.As powder filling for fixing the helix within the glow tube magnesium oxide is usually used. The heat conductor alloy protects against annealing in the air within a very short time by the formation of a thin α-Al 2 O 3 layer against further corrosion. However, this requirement is not given in glow plugs due to an initial lack of oxygen in the embedded state of the heating coil in the insulating powder. However, during cyclic thermal stress during use, the glow plug "breathes". As a result, small amounts of air in the interior of the glow plug, ie the cavity, which should be sealed by the Viton gasket, penetrate, so that it comes to the simultaneous reaction of the Heizwendelmaterials with oxygen and nitrogen. Nitrogen, unlike oxygen, which forms a protective alumina layer on the surface of the heating coil, results in the formation of aluminum nitride inside the coil. The formation of Aluminiumiunmitrid inside the coil has a local increase in electrical resistance and thus an early failure of the heating coil of the glow plug result. In addition, chemical reactions with powder impurities may occur on the metallic surface of the heating coil at higher temperatures, which may be contained in the insulating powder, which may likewise lead to premature damage to the heating coil and failure of the annealing function.

Offenbarung der ErfindungDisclosure of the invention

Erfindungsgemäß wird vorgeschlagen, die Heizwendel der Glühstiftkerze vor dem bestimmungsgemäßen Gebrauch der Glühstiftkerze einer thermischen Behandlung zu unterziehen, derart, dass an der Oberfläche der Heizwendel eine Beschichtung als Schutzschicht entsteht. Die Beschichtung ist dabei eine Oxidschicht, die sich durch Oxidation eines Legierungsbestandteils des Materials der Heizwendel aufgrund der thermischen Behandlung der Heizwendel ausbildet.According to the invention, it is proposed to subject the heating coil of the glow plug prior to the intended use of the glow plug of a thermal treatment, such that on the surface of the heating coil, a coating is formed as a protective layer. The coating is an oxide layer which is formed by oxidation of an alloy constituent of the material of the heating coil due to the thermal treatment of the heating coil.

Die Beschichtung mittels Voroxidation erfolgt bei einem relativ hohen Sauerstoffdruck, z. B. in einer reinen Sauerstoffatmosphäre oder in Luft. Eine besonders wirksame Schutzschicht durch Voroxidation wird bei Verwendung eines mit Aluminium legierten Materials der Heizwendel erreicht, wobei der Aluminiumbestandteil des Materials der Heizwendel durch die thermische Behandlung der Heizwendel an der Oberfläche der Heizwendel eine α-Al2O3-Schicht ausbildet. Sobald sich auf der Oberfläche der Heizwendel die α-Al2O3-Schicht gebildet hat, ist das Material der Heizwendel wirksam geschützt, so dass chemische Reaktionen verhindert werden. Die α-Al2O3-Schicht bewirkt eine Erhöhung der Lebensdauer der Glühstiftkerze durch ihre Schutzfunktion. Schädigende chemische Reaktionen können beispielsweise durch die Bildung von Aluminiumnitrid im Inneren des Wendelmaterials oder auch durch chemische Reaktion von chemischen Fremdbestandteilen des Magnesiumoxides ausgehen. Diese chemischen Reaktionen sind mit dem Nachteil verbunden, dass diese eine Anfangsschädigung des Materials der Heizwendel bewirken und somit die Betriebszeit der Glühstiftkerze höchst negativ beeinflussen.The coating by means of pre-oxidation takes place at a relatively high oxygen pressure, for. B. in a pure oxygen atmosphere or in air. A particularly effective Protective layer by pre-oxidation is achieved when using an alloyed aluminum material of the heating coil, wherein the aluminum component of the material of the heating coil by the thermal treatment of the heating coil on the surface of the heating coil forms an α-Al 2 O 3 layer. Once formed on the surface of the heating coil, the α-Al 2 O 3 layer, the material of the heating coil is effectively protected, so that chemical reactions are prevented. The α-Al 2 O 3 layer causes an increase in the life of the glow plug by its protective function. Damaging chemical reactions can be caused, for example, by the formation of aluminum nitride in the interior of the helical material or by chemical reaction of foreign chemical constituents of the magnesium oxide. These chemical reactions are associated with the disadvantage that they cause an initial damage to the material of the heating coil and thus have the most adverse effect on the operating time of the glow plug.

In einer nicht zur Erfindung gehörigen Auführungsform wird die als Heizwendel eingesetzte Glühwendel in eine geeignete Aufnahme gespannt und vorzugsweise leicht auseinandergezogen werden. Durch das in einer horizontalen oder vertikalen Ebene erfolgende Auseinanderziehen der einzelnen Windungen der Heizwendel wird verhindert, dass die einzelnen Windungen in Kontakt miteinander stehen. Dadurch wird eine größere Oberfläche zur Bildung der α-Al2O3-Schicht geschaffen, d. h. es ist der erfindungsgemäß vorgeschlagenen Lösung und dem daraus hervorgehenden Verfahrens folgend, gewährleistet, dass sich an der gesamten Oberfläche des als Heizwendel eingesetzten, bevorzugt in Drahtform vorliegenden Wendelmaterials die besagte α-Al2O3-Schicht ausbildet, die das Material der Wendel in oben geschilderter Weise gegen chemische Reaktionen schützt. Anschließend kann selektiv der Heizwendelteil, d. h. der Teil des Wendelmaterials, der im Glührohr am brennraumseitigen Ende aufgenommen ist, unter Anlegen einer äußeren Spannung zwischen 1000 °C und 1300 °C in einer Zeitspanne von 30 s bis 15 min geglüht werden. Dadurch wird die Bildung einer Oxidschicht auf dem Material der Heizwendel gefördert. In bevorzugter Ausgestaltung des erfindungsgemäß vorgeschlagenen Verfahrens kann die Heizwendel bei einer Temperatur von 1200 °C für 10 min geglüht werden. Beim Glühen der Heizwendel oder des Heizwendelabschnittes im Glührohr ist dafür Sorge zu tragen, dass die Regelwendel nicht bei einem derartigen Spannungsniveau geglüht wird.In an embodiment not belonging to the invention, the filament used as a heating coil is clamped in a suitable receptacle and preferably pulled apart easily. By taking place in a horizontal or vertical plane pulling apart of the individual turns of the heating coil prevents the individual turns are in contact with each other. This creates a larger surface area for the formation of the α-Al 2 O 3 layer, ie following the solution proposed according to the invention and the method resulting therefrom, it is ensured that on the entire surface of the helical material used as a heating coil, preferably in wire form forms said α-Al 2 O 3 layer, which protects the material of the coil in the manner described above against chemical reactions. Subsequently, the Heizwendelteil, ie, the part of the helical material, which is received in the glow tube at the combustion chamber end, selectively, under application of an external stress between 1000 ° C and 1300 ° C in a period of 30 s to 15 minutes are annealed. This promotes the formation of an oxide layer on the material of the heating coil. In a preferred embodiment of the method proposed by the invention, the heating coil can be annealed at a temperature of 1200 ° C for 10 min. When annealing the heating coil or the Heizwendelabschnittes in the glow tube is to ensure that the control coil is not annealed at such a voltage level.

Nach Vornahme des Glühens der Heizwendel beziehungsweise des Heizwendelabschnittes wird die Heizwendel wie üblich in der Glühstiftkerze verbaut.After making the glow of the heating coil or the Heizwendelabschnittes the heating coil is installed as usual in the glow plug.

Alternativ zum vorstehend Gesagten, kann die Heizwendel erfindungsgemäß nach dem Verbinden mit einem Anschlussbolzen und nach dem Einbringen ins Glührohr durch eine das Glührohr an der Außenmantelfläche umschließende Induktionsspule passiv geglüht werden. Auch beim Passivglühen ist sicherzustellen, dass die außen anliegende Induktionsspule nur den vorderen Teil des Wendelmaterials d.h. die Heizwendel erfasst, und nicht die Regelwendel, die dieser Wärmebehandlung nicht ausgesetzt werden sollte.As an alternative to the above, according to the invention the heating coil can be passively annealed after being connected to a connecting bolt and after being introduced into the glow tube by an induction coil enclosing the glow tube on the outer circumferential surface. Also in passive annealing, make sure that the outside induction coil only covers the front part of the helix material, i. detects the heating coil, and not the control coil, which should not be exposed to this heat treatment.

Beschreibung der ZeichnungenDescription of the drawings

Anhand der Zeichnung wird die Erfindung nachstehend eingehender beschrieben.With reference to the drawing, the invention will be described below in more detail.

Es zeigen:

Figur 1
einen Schnitt durch die Glühstiftkerze mit in ein Glührohr eingelassener Heizwendel und mit einer Regelwendel,
Figur 2
einen nicht zur Erfindung gehörigen Aufbau zur Voroxidation der Heizwendel und
Figur 3
in schematischer Weise ein induktives Vorglühen der Heizwendel.
Show it:
FIG. 1
a section through the glow plug with embedded in a glow tube heating coil and with a control coil,
FIG. 2
a not belonging to the invention structure for pre-oxidation of the heating coil and
FIG. 3
in a schematic way, an inductive preheating of the heating coil.

Ausführungsformenembodiments

Figur 1 zeigt, dass eine Glühstiftkerze 10 ein Gehäuse 12 umfasst, in welches ein Anschlussbolzen 14 eingelassen ist. Der Anschlussbolzen 14 ist über einen Rundstecker 18 oder eine anders gestaltete Schraub- oder Klemmverbindung mit einem Pluspol einer Strom- oder Spannungsquelle verbunden. Unterhalb des Rundsteckers 18 befindet sich eine Isolierscheibe 20 zur Isolierung des Gehäuses 14 gegen den Rundstecker 18. Unterhalb der Isolierscheibe 20 befindet sich eine Gehäusedichtung 16. Über die Gehäusedichtung 16 ist ein Hohlraum innerhalb des Gehäuses 12, in welchem der Anschlussbolzen 14 aufgenommen ist, gegen die Umgebung abgedichtet. Unterhalb des Anschlussbolzens 14 befindet sich innerhalb des Gehäuses 12 eine Heizkörperdichtung 22, die zum Beispiel als eine Vitondichtung ausgebildet sein kann. Mit dieser Heizkörperdichtung 22 ist der Anschlussbolzen 14 einerseits im Gehäuse 12 fixiert und andererseits gegen ein Glührohr 24 abgedichtet. Das Glührohr 24 ist dünnwandig ausgeführt, wobei seine Wand 26 einen Hohlraum umschließt und die Wand 26 die wärmeabgebende Mantelfläche 28 darstellt. Im Hohlraum des Glührohrs 24 befinden sich eine Regelwendel 30 und eine Heizwendel 32. Die Regelwendel 30 und die Heizwendel 32 sind an einer Fügestelle 40 miteinander stoffschlüssig verbunden. Der Hohlraum innerhalb des Glührohrs 24 ist mit einem Isoliermaterial 34 befüllt, bei dem es sich bevorzugt um Magnesiumoxid handelt. Die Regelwendel 30 ist mit einem Anschluss unterhalb des Anschlussbolzens 14, vergleiche Bezugszeichen 38, verbunden. Mit Bezugszeichen 36 ist die Fügestelle der Heizwendel 32 mit der Spitze des Glührohrs 24 bezeichnet. FIG. 1 shows that a glow plug 10 comprises a housing 12, in which a connecting bolt 14 is inserted. The connecting bolt 14 is connected via a circular connector 18 or a differently designed screw or clamp connection with a positive pole of a current or voltage source. Below the circular connector 18 is an insulating disc 20 for insulating the housing 14 against the circular connector 18. Below the insulating washer 20 is a housing seal 16. About the housing seal 16 is a cavity within the housing 12, in which the connecting bolt 14 is received against the environment sealed. Below the connecting bolt 14 is located within the housing 12, a radiator seal 22, which may be formed, for example, as a Viton seal. With this radiator seal 22 of the connecting bolt 14 is fixed on the one hand in the housing 12 and on the other hand sealed against a glow tube 24. The glow tube 24 is made thin-walled, with its wall 26 enclosing a cavity and the wall 26 is the heat-emitting lateral surface 28. In the cavity of the glow tube 24 are a control coil 30 and a heating coil 32. The control coil 30 and the heating coil 32 are connected to each other at a joint 40 cohesively. The cavity within the glow tube 24 is filled with an insulating material 34, which is preferably magnesium oxide. The control coil 30 is connected to a connection below the connecting bolt 14, see reference numeral 38. Reference numeral 36 denotes the joint of the heating coil 32 with the tip of the glow tube 24.

Der Darstellung in Figur 3 lässt sich in schematischer Weise eine Anordnung zur Durchführung der erfindungsgemäß vorgeschlagenen Behandlung der Heizwendel der Glühstiftkerze gemäß Figur 1 entnehmen.The representation in FIG. 3 can be in a schematic manner an arrangement for carrying out the invention proposed treatment of the heating coil of the glow plug according to FIG. 1 remove.

Figur 2 zeigt eine nicht zur Erfindung gehörige Vorrichtung zum Aufnehmen der unverbauten Heizwendel 32 mit einem ersten Aufnahmeteil 52 und einem zweites Aufnahmeteil 54. Sowohl das erste Aufnahmeteil 52 als auch das zweite Aufnahmeteil 54 sind mit einer Trägerplatte 58 unter Einbeziehung mindestens einer elektrischen Isolation 60 verbunden. Sowohl das erste Aufnahmeteil 52 als auch das zweite Aufnahmeteil 54 umfassen Einrichtungen zum Aufbringen einer Horizontalvorspannung. So können zum Beispiel das erste Aufnahmeteil 52 und das zweite Aufnahmeteil 54 jeweils mit Gewindeabschnitten versehen sein, durch welche Bolzenkörper 68 - wie in Figur 2 angedeutet - in horizontaler Zugrichtung, vergleiche Pfeil 62, auseinander gezogen werden können. Zwischen den einander zuweisenden Stirnseiten der Spannbolzen 68 ist eine Heizwendel 32 eingespannt. Die Enden von Einzelwindungen 55 der Heizwendel 32 sind mit den einander zuweisenden Stirnseiten der beiden Spannbolzen 68 verbunden. Des Weiteren können die beiden Spannbolzen 68 über Anschlusskabel 66 mit einer Spannungsquelle 50 in Verbindung gebracht werden. Dem erfindungsgemäß vorgeschlagenen Verfahren folgend, wird nach dem Einspannen und Befestigen der offenen Windungen 55 der Heizwendel 32 zwischen die einander zuweisenden Stirnseiten der Spannbolzen 68 eine in Axialrichtung wirkende Kraft aufgebracht, durch welche die einzelnen Windungen 55 der Heizwendel 32 in horizontale Zugrichtung 62 auseinandergezogen werden. Demnach werden die einzelnen Windungen 55 der Heizwendel 32 in horizontale Richtung gestreckt, bis das Material der einzelnen Windungen 55 in einen Abstand 64 gebracht ist, d. h. die einzelnen Windungen 55 der Heizwendel 32 einander nicht mehr kontaktieren. Dies bedeutet, dass die gesamte Oberfläche der Heizwendel 32 nunmehr einer Sauerstoffatmosphäre oder der Luft ausgesetzt ist. Der in der Luft enthaltene Sauerstoff reagiert mit der Oberfläche der Heizwendel 32, derart, dass sich an dieser insbesondere an dem gesamten Umfang der einzelnen Windungen 55 eine α-Al2O3-Beschichtung ausbildet. Diese α-Al2O3-Beschichtung ist durch eine kubische Gitterstruktur gekennzeichnet. Der in der Luft enthaltende Stickstoff reagiert wesentlich langsamer mit der Oberfläche der Heizwendel 32. Aufgrund der schnelleren Reaktion des in der Luft enthaltenden Sauerstoffs bildet sich die α-Al2O3-Beschichtung wesentlich schneller aus, so dass die Oberfläche der Heizwendel 32 gegen eine chemische Reaktion mit dem in der Luft enthaltenen Stickstoff sehr schnell geschützt ist. FIG. 2 shows a not belonging to the invention device for receiving the unconverted heating coil 32 having a first receiving part 52 and a second receiving part 54. Both the first receiving part 52 and the second receiving part 54 are connected to a support plate 58 including at least one electrical insulation 60. Both the first receiving part 52 and the second receiving part 54 include means for applying a horizontal bias. Thus, for example, the first receiving part 52 and the second receiving part 54 may each be provided with threaded portions through which bolt body 68 - as in FIG. 2 indicated - in the horizontal direction of pull, see arrow 62, can be pulled apart. Between the facing end faces of the clamping bolt 68, a heating coil 32 is clamped. The ends of individual turns 55 of the heating coil 32 are connected to the mutually facing end faces of the two clamping bolts 68. Furthermore, the two clamping bolts 68 can be brought via connecting cable 66 with a voltage source 50 in connection. Following the proposed method according to the invention, after clamping and securing the open turns 55 of the heating coil 32 between the facing end faces of the clamping bolt 68 is applied an axially acting force through which the individual turns 55 of the heating coil 32 are pulled apart in the horizontal direction of pull 62. Accordingly, the individual turns 55 of the heating coil 32 in the horizontal direction stretched until the material of the individual turns 55 is brought into a distance 64, that is, the individual turns 55 of the heating coil 32 no longer contact each other. This means that the entire surface of the heating coil 32 is now exposed to an oxygen atmosphere or the air. The oxygen contained in the air reacts with the surface of the heating coil 32, such that an α-Al 2 O 3 coating is formed thereon, in particular on the entire circumference of the individual turns 55. This α-Al 2 O 3 coating is characterized by a cubic lattice structure. The nitrogen in the air reacts much more slowly with the surface of the heating coil 32. Due to the faster reaction of oxygen in the air containing the α-Al 2 O 3 coating forms much faster, so that the surface of the heating coil 32 against a chemical reaction with the nitrogen contained in the air is very quickly protected.

Nach dem Strecken der Heizwendel 32 in der in Figur 2 schematisch angedeuteten Vorrichtung lässt sich an der gesamten Oberfläche des Materials der Heizwendel 32 eine α-Al2O3-Beschichtung erzeugen.After stretching the heating coil 32 in the in FIG. 2 schematically indicated device can be produced on the entire surface of the material of the heating coil 32, an α-Al 2 O 3 coating.

Ist die Heizwendel 32 in die in Figur 2 dargestellte Vorrichtung eingespannt, so können die beiden Spannbolzen 68 über die Spannungsquelle 50 beziehungsweise die Anschlusskabel 66 direkt bestromt werden. Dies bedeutet, dass die Heizwendel 32 in gestreckter Anordnung innerhalb der in Figur 2 dargestellten Vorrichtung direkt beheizt, d. h. direkt geglüht werden kann. Das Glühen der Heizwendel 32 erfolgt während einer Zeitspanne, die zwischen 30 s und 5 min liegt. Während dieser Zeitspanne wird in der Heizwendel 32 eine Temperatur im Temperaturbereich zwischen 1000 °C und 1300 °C erzeugt. Besonders gute Ergebnisse hinsichtlich einer gleichmäßigen Ausbildung der α-Al2O3-Beschichtung an der gesamten Oberfläche des Materials der Heizwendel 32 haben sich während einer Glühdauer von 10 min bei einer Temperatur von 1200 °C eingestellt. Je nach Applikationszweck und Durchmesser des Wendeldrahtes sowie Anzahl der Windungen 55 der Heizwendel 32 können auch unterschiedliche Glühdauern realisiert werden. Dies hängt in nicht unerheblichem Maße vom Durchmesser des Materials der Windungen 55 sowie von der Gesamtanzahl der Windungen 55 der Heizwendel 32 ab.Is the heating coil 32 in the in FIG. 2 clamped device shown, the two clamping bolts 68 can be energized directly via the voltage source 50 and the connecting cable 66. This means that the heating coil 32 in a stretched arrangement within the in FIG. 2 directly heated device shown, ie can be annealed directly. The annealing of the heating coil 32 takes place during a period of time which is between 30 s and 5 min. During this period, a temperature in the temperature range between 1000 ° C and 1300 ° C is generated in the heating coil 32. Particularly good results in terms of a uniform formation of the α-Al 2 O 3 coating on the entire surface of the material of the heating coil 32 have been set at a temperature of 1200 ° C during an annealing time of 10 min. Depending on the application purpose and diameter of the helical wire and number of turns 55 of the heating coil 32, different annealing times can be realized. This depends to a considerable extent on the diameter of the material of the turns 55 and the total number of turns 55 of the heating coil 32 from.

In diesem Zusammenhang ist darauf hinzuweisen, dass mit dieser Behandlung ausschließlich die Heizwendel 32 zu behandeln ist und nicht die in Figur 1 dargestellte, sich zwischen dem Anschlussbolzen 14 und der Heizwendel 32 erstreckende, mit Bezugszeichen 30 bezeichnete Regelwendel. Durch das Auseinanderziehen, d. h. das Strecken der Heizwendel 32 in der in Figur 2 schematisch angedeuteten Vorrichtung, lässt sich erreichen, dass die gesamte Oberfläche des im Wesentlichen drahtförmig vorliegenden Materials der Heizwendel 32 der Luft beziehungsweise einer Sauerstoffatmosphäre ausgebildet ist, ausgesetzt werden kann, so dass eine gleichmäßige Ausbildung der α-Al2O3-Beschichtung an der Oberfläche des Materials der Heizwendel 32 erfolgt. Damit ist die Heizwendel 32 durch die Voroxidation gegen chemische Reaktionen geschützt, die zum Beispiel dadurch auftreten können, dass im Isoliermaterial 34, in welches die Heizwendel 32 sowie die Regelwendel 30 eingebettet sind, Verunreinigungen enthalten sein können, die zu chemischen Reaktionen führen. Aufgrund der vor Montage der Heizwendel 32 in dem Glührohr 24 erzeugten α-Al2O3-Beschichtung ist das Material gegen derartige chemische Reaktionen geschützt, so dass die Lebensdauer einer derart hergestellten Glühstiftkerze 10 entscheidend verlängert werden kann.In this context, it should be noted that this treatment is to treat only the heating coil 32 and not the in FIG. 1 shown, extending between the terminal bolt 14 and the heating coil 32 extending, designated by reference numeral 30 control coil. By pulling apart, ie stretching the heating coil 32 in the in FIG. 2 schematically indicated device, it can be achieved that the entire surface of the substantially wirelike material of the heating coil 32 of the air or an oxygen atmosphere is formed, can be exposed, so that a uniform formation of the α-Al 2 O 3 coating on the surface the material of the heating coil 32 takes place. Thus, the heating coil 32 is protected by the pre-oxidation against chemical reactions that may occur, for example, that in the insulating material 34, in which the heating coil 32 and the control coil 30 are embedded, impurities may be present that lead to chemical reactions. Due to the α-Al 2 O 3 coating produced before assembly of the heating coil 32 in the glow tube 24, the material is protected against such chemical reactions, so that the life of a glow plug 10 produced in this way can be significantly extended.

Bevorzugt wird die Behandlung der Oberfläche des Materials der Heizwendel 32 in einer zum Beispiel mit Sauerstoff angereicherten Atmosphäre durchgeführt.Preferably, the treatment of the surface of the material of the heating coil 32 is performed in an oxygen-enriched atmosphere, for example.

Der Darstellung gemäß Figur 3 ist ein passives Vorglühen der Heizwendel gemäß der Erfindung einer Glühstiftkerze zu entnehmen. Dieses Ausführungsbeispiel lässt sich besonders vorteilhaft in den Fertigungsprozess der Glühstiftkerze integrieren.The representation according to FIG. 3 is to take a passive preheating of the heating coil according to the invention of a glow plug. This embodiment can be integrated particularly advantageous in the manufacturing process of the glow plug.

Aus der schematischen Darstellung gemäß Figur 3 geht hervor, dass in dieser Ausgestaltungsvariante die Heizwendel 32, verbunden mit der Regelwendel 30, im Isolationsmaterial 34, welches im Glührohr 24 aufgenommen ist, eingebettet ist. In dieser Ausgestaltungsvariante des erfindungsgemäß vorgeschlagenen Verfahrens sind die Regelwendel 30 und die Heizwendel 32 mit dem Anschlussbolzen 14 elektrisch verbunden. Des Weiteren steht die Regelwendel 30 mit der Heizwendel 32 in elektrischem Kontakt, da beide an der Fügestelle 40 miteinander verbunden sind. Des Weiteren ist die Heizwendel 32 in der Darstellung gemäß Figur 3 mit einer Spitze 72 des Glührohrs 24 verbunden. Das Glührohr 24, welches mit dem Isolationsmaterial 34, bei dem es sich bevorzugt um Magnesiumoxid handelt, befüllt ist, nimmt sowohl die Regelwendel 30 als auch die Heizwendel 32 auf. Das Glührohr 24 umfasst die Wand 26, die dünnwandig ausgebildet ist, um einen besseren Wärmetransport zu ermöglichen. Die Mantelfläche 28 des Glührohrs 24 gemäß der schematischen Darstellung in Figur 3 ist von einer Induktionsspule 70 umschlossen. Die Induktionsspule 70 umfasst eine Anzahl von Windungen, welche die Mantelfläche 28 des Glührohrs 24 nur in dem Bereich umschließen, in dessen Inneren die Heizwendel 32 aufgenommen ist. Demnach wird die Regelwendel 30, die mit der Heizwendel 32 und dem Anschlussbolzen 14 elektrisch kontaktiert ist, nicht von den Windungen der Induktionsspule 70 umgeben. Die Induktionsspule 70 ist analog zur Darstellung gemäß Figur 2 mit einer Spannungsbeziehungsweise Stromquelle 50 über in Figur 3 ebenfalls nicht dargestellte Anschlusskabel verbunden.From the schematic representation according to FIG. 3 shows that in this embodiment variant, the heating coil 32, connected to the control coil 30, in the insulating material 34, which is accommodated in the glow tube 24, is embedded. In this embodiment variant of the method proposed according to the invention, the control coil 30 and the heating coil 32 are electrically connected to the connecting bolt 14. Furthermore, the control coil 30 is in electrical contact with the heating coil 32, since both are connected to one another at the joint 40. Furthermore, the heating coil 32 in the illustration according to FIG. 3 connected to a tip 72 of the glow tube 24. The glow tube 24, which is filled with the insulating material 34, which is preferably magnesium oxide, receives both the control coil 30 and the heating coil 32. The glow tube 24 includes the wall 26, the thin-walled is formed to allow a better heat transfer. The lateral surface 28 of the glow tube 24 according to the schematic representation in FIG. 3 is enclosed by an induction coil 70. The induction coil 70 comprises a number of turns, which enclose the lateral surface 28 of the glow tube 24 only in the region in the interior of which the heating coil 32 is accommodated. Accordingly, the control coil 30, which is electrically contacted with the heating coil 32 and the terminal bolt 14, not surrounded by the turns of the induction coil 70. The induction coil 70 is analogous to the representation according to FIG FIG. 2 with a voltage or current source 50 over in FIG. 3 also not shown connecting cable connected.

Wird die Induktionsspule 70 mit der Spannungsquelle 50 verbunden, der Stromkreis geschlossen, so erfolgt ein Passivglühen der Heizwendel 32, die in diesem Zustand montiert im Glührohr 24 aufgenommen ist. Beim Passivglühen der Heizwendel 32 erfolgt deren Beheizung auf Temperaturen von 1000°C bis 1200°C während einer Zeitspanne von 3 min bis 15 min, bevorzugt bei 1200°C für etwa 10 min. Auch bei dem Passivglühen in dem in das Glührohr 24 einbauten Zustand der Heizwendel 32 erfolgt zumindest während der thermischen Behandlung der Heizwendel 32 ein Strecken der Heizwendel 32. Dabei wird mit geeigneten Mitteln beispielsweise der Anschlussbolzen 14 in vertikaler Richtung aus dem Glührohr 24 um einen Betrag gezogen, so dass die Windungen der Heizwendel 32 voneinander beabstandet sind, so wie im Zusammenhang mit Figur 2 beschrieben wurde. Dadurch wird gewährleistet, dass die Beschichtung an der gesamten Oberfläche der Heizwendel 32 entstehen kann.If the induction coil 70 is connected to the voltage source 50, the circuit is closed, then a passive annealing of the heating coil 32, which is received in this state mounted in the glow tube 24. During passive annealing of the heating coil 32, its heating takes place at temperatures of 1000 ° C. to 1200 ° C. for a period of 3 min to 15 min, preferably at 1200 ° C. for about 10 min. Even with the passive annealing in the installed in the glow tube 24 state of the heating coil 32 is at least during the thermal treatment of the heating coil 32, a stretching of the heating coil 32. In this case, for example, the connecting bolt 14 is pulled in the vertical direction from the glow tube 24 by an amount by suitable means in that the turns of the heating coil 32 are spaced apart from each other, as associated with FIG. 2 has been described. This ensures that the coating can be formed on the entire surface of the heating coil 32.

Durch das erfindungsgemäß vorgeschlagene Verfahren bei einer indirekten Beheizung der Heizwendel 32 über eine diese umgebende Induktionsspule 70, lässt sich eine Voroxidation der Heizwendel 32 der Glühstiftkerze 10 erreichen. Die Voroxidation verhindert chemische Reaktionen des blanken metallischen Materials der Heizwendel 32 bei dessen Einbettung in das Isolationsmaterial 34, da dieses verunreinigt sein kann. Des Weiteren bietet die α-Al2O3-Schicht auf der Oberfläche der Windungen 55 der Heizwendel 32 eine Erhöhung der Lebensdauer der Glühstiftkerze 10, da diese Beschichtung eine Schutzfunktion ausübt und verhindert, dass chemische Reaktionen mit dem Grundmaterial der Heizwendel 32 zustande kommen.By the method proposed according to the invention with an indirect heating of the heating coil 32 via an induction coil 70 surrounding it, a pre-oxidation of the heating coil 32 of the glow plug 10 can be achieved. The pre-oxidation prevents chemical reactions of the bare metallic material of the heating coil 32 when it is embedded in the insulating material 34, since this can be contaminated. Furthermore, the α-Al 2 O 3 layer on the surface of the turns 55 of the heating coil 32 provides an increase in the life of the glow plug 10, since this coating performs a protective function and prevents chemical reactions with the base material of the heating coil 32 come about.

Claims (5)

  1. Process for producing a sheathed-element glow plug (10) having at least one heater coil (32), in particular for treating the heater coil (32), wherein the heater coil is arranged in a glow tube (24), the glow tube (24) is fastened in a housing (12) and the heater coil (32) is subjected to heat treatment, in such a manner that a coating forms on the surface of the heater coil (32), said coating being formed as an oxide layer of an alloy constituent of the material of the heater coil (32) on account of the heat treatment to which the heater coil (32) is subjected, characterized in that the heater coil (32) is annealed after it has been connected to a connection pin (14) and after it has been introduced into the glow tube (24) by an induction coil (70) which surrounds the glow tube (24) on an outer lateral surface (28) in the region of the heater coil (32), wherein at least during the heat treatment the heater coil (32) is stretched, in such a manner that the turns (55) are spaced apart from one another, wherein furthermore said heater coil is heated to temperatures of 1000°C to 1200°C over a period of time of 3 minutes to 15 minutes.
  2. Process according to Claim 1, characterized in that a material alloyed with aluminium is used for the heater coil (32), and in that an α-Al2O3 coating is produced on the surface of the heater coil (32) by means of the heat treatment to which the heater coil (32) is subjected.
  3. Process according to either of the preceding claims, characterized in that the heater coil (32) is annealed at 1200°C for 10 minutes.
  4. Process according to one of the preceding claims, characterized in that the heat treatment for preoxidation of the heater coil (32) is carried out under an oxygen atmosphere or in air.
  5. Process according to one of Claims 1 to 4, characterized in that the heater coil (32) is annealed directly by applying a voltage in the non-assembled state.
EP07122574A 2007-01-11 2007-12-07 Manufacturing process for a glow plug Not-in-force EP1944551B1 (en)

Applications Claiming Priority (1)

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DE200710001648 DE102007001648A1 (en) 2007-01-11 2007-01-11 glow plug

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EP1944551B1 true EP1944551B1 (en) 2012-06-27

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DE102011007347A1 (en) 2011-04-14 2012-10-18 Robert Bosch Gmbh Heater plug for diesel engine in into modern motor car, has glow pipe including functional coating placed in combustion chamber section, where coating is formed with aluminum oxide film and underlying memory diffusion layer
DE102012200256A1 (en) 2012-01-10 2013-07-11 Robert Bosch Gmbh glow plug
CA2872451C (en) 2012-05-16 2018-02-06 Babcock & Wilcox Volund A/S Heat exchanger having enhanced corrosion resistance
CN114855100B (en) * 2022-05-11 2023-04-25 烟台卓越新能源科技股份有限公司 Pretreatment method and continuous pretreatment device for electric heating wire

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JPS61107013A (en) * 1984-10-31 1986-05-24 Ngk Spark Plug Co Ltd Ceramic glow plug
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EP0635993B1 (en) * 1993-07-20 2000-05-17 TDK Corporation Ceramic heater
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DE102005024622A1 (en) * 2005-05-30 2006-12-07 Beru Ag Pencil-type glow plug has holder and metal ignition rod is arranged in metal ignition tube whereby high temperature resistant material coating is provided partly at metal ignition tube which is projecting from holder

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EP1944551A1 (en) 2008-07-16

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