EP0480886A1 - Bougie d'allumage - Google Patents

Bougie d'allumage Download PDF

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Publication number
EP0480886A1
EP0480886A1 EP91830415A EP91830415A EP0480886A1 EP 0480886 A1 EP0480886 A1 EP 0480886A1 EP 91830415 A EP91830415 A EP 91830415A EP 91830415 A EP91830415 A EP 91830415A EP 0480886 A1 EP0480886 A1 EP 0480886A1
Authority
EP
European Patent Office
Prior art keywords
insulator
central electrode
ring
spark plug
electrode
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.)
Withdrawn
Application number
EP91830415A
Other languages
German (de)
English (en)
Inventor
Pietro De Filippis
Roberto Rossi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Industrie Magneti Marelli SRL
Marelli Europe SpA
Original Assignee
Industrie Magneti Marelli SRL
Magneti Marelli SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Industrie Magneti Marelli SRL, Magneti Marelli SpA filed Critical Industrie Magneti Marelli SRL
Publication of EP0480886A1 publication Critical patent/EP0480886A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/39—Selection of materials for electrodes

Definitions

  • the present invention relates to spark plugs for internal combustion engines with controlled ignition.
  • the invention relates to a spark plug of the type comprising: a tubular, outer, metal body, a tubular insulator disposed in the body, a central electrode which extends through the insulator and projects axially from its end which faces the combustion chamber in use, and at least one earth electrode which extends from the outer metal body towards the side surface of that portion of the central electrode which projects from the insulator.
  • An object of the invention is to provide a spark plug of this type which is suitable for greatly extended operation (a "long-life" plug).
  • a known "long-life" plug has an earth electrode which, according to well-known geometry, extends from the metal outer body of the plug to face the end surface or face of the central electrode. Coatings of noble metal, typically platinum or alloys thereof, are welded to the end surface of the central electrode and the facing portion of the earth electrode between which the spark is struck in use.
  • the object of the present invention is to provide a "long-life" plug which does not have the disadvantages of those of the prior art.
  • this object is achieved by a spark plug of the type specified above, whose main characteristic lies in the fact that a ring of noble metal or an alloy thereof is disposed around the projecting portion of the central electrode, in electrical contact therewith, so that the spark or sparks jump between the ring and the at least one earth electrode in operation.
  • a spark plug according to the invention for an internal combustion engine is generally indicated 1.
  • the plug includes, in known manner, a tubular, outer metal body 2 with an externally threaded portion.
  • a substantially tubular element 3 of electrically-insulating, typically ceramic, material is disposed in the body 2 in known manner ( Figure 2).
  • An end portion 3a of the insulator projects axially from the end of the metal body 2 which faces the combustion chamber in use.
  • a central electrode, indicated 4 extends through part of the insulator 3 and projects axially from its end 3a.
  • a conductive core 5 is also disposed in the insulator. One end of the core projects axially from the insulating element 3 and constitutes an electrical connecting terminal 6.
  • a conductive or resistive sealing mastic is interposed between the central electrode 4 and the conductive core 5 within the insulating element 3.
  • a metal ring, onto which an end edge 2a of the metal body 2 is upset, is indicated 8 ( Figure 2).
  • the ring 6 is made, for example, of a nickel- or copper-based alloy and has a plurality of integral appendages 9 which extend from its inner edge towards the end portion 3a of the insulator in equiangularly-spaced positions.
  • the appendages constitute the earth electrodes of the plug.
  • the ring 8 with its integral appendages 9 which act as electrodes may be welded to the end of the metal outer body 2 of the plug, for example, by laser welding.
  • the central electrode 4 has a substantially disc-shaped head 4a.
  • a ring, indicated 10, of noble metal (for example, platinum) or an alloy thereof, is disposed around the central electrode 4 between its head 4a and the end 3a of the insulator 3 ( Figure 2).
  • the noble metal ring may simply be fitted around the electrode and then clamped between its head 4a and the insulator 3 or may be placed around the stem of the central electrode 4 and then welded to its head 4a.
  • the arrangement is such that, in operation, the sparks jump between the noble metal ring 10 and the earth electrodes 9.
  • the end 4b of the central electrode opposite its head 4a has one or more transverse diametral slots, one of which, indicated 11, can be seen in Figure 2.
  • the portions of the end 4b adjacent the slots 11 are shown opened out.
  • the end 4b of this electrode can thus be inserted in the insulating element 3 through its end 3a until the end 4b projects into a larger-diameter central portion 3b of the duct defined in the insulator 3.
  • the end 4b of the central electrode is opened out by a tool (inserted into the insulator from its end opposite the end 3a); the central electrode can thus no longer be removed and separated from the insulator 3.
  • a quantity of sealing mastic 7 is then introduced into the portion 3b of the axial duct in the insulator 3 and the conductive core 5 is then inserted in the insulator 3.
  • the resistive sealing mastic 7 is squashed between the central electrode 4 and the conductive core 5 by the application of opposing forces in the directions of the arrows F in Figure 2. This operation involves a risk that the end portion 3a of the insulator 3 may be damaged by the formation of cracks or other flaws which are not readily detectable but which may compromise the efficiency and functionality of the plug in operation and, in particular, reduce its life.
  • the central electrode 4 is generally cylindrical and does not have a head on its end portion which is intended to face the combustion chamber. Its opposite end which, in this embodiment, is again indicated 4b is shaped so that it can "mate” by form-coupling with an internal tapered shoulder 3c defined in the axial duct in the insulator 3.
  • the central electrode 4 can thus be inserted in the insulator 3 from its end opposite the end 3a.
  • a ring 10 of noble metal or an alloy thereof is welded around the end 4a of the electrode 4 which projects from the insulator 3.
  • a quantity of resistive sealing mastic 7 can then be inserted in the axial duct 3b of the insulator 3 and squashed under pressure exerted solely by the core 5, whilst the ceramic insulator 3 is restrained by its tapered lateral surface where it is less delicate, without the risk of damage to its tip 3a.
  • the arrangement of the noble metal ring 10 is also such that, in operation, the sparks jump between the ring and the earth electrodes 9.
  • Figure 4 shows a variant in which the plug 1 includes one (or more) substantially arcuate earth electrodes 19 connected (for example, by welding) to the annular end surface of the metal body 2 with their ends facing the noble metal ring 10 which is welded to the central electrode 4.
  • part of the end surface of each earth electrode 19 also faces the ceramic insulator 3 and this plug is therefore of the partial-surface-discharge type.
  • the noble metal ring 10 has a smaller diameter than the end 3a of the ceramic insulator 3.
  • Figures 5 and 6 show two embodiments similar to those illustrated in Figures 3 and 4 respectively but with the noble metal ring 10 projecting radially from the insulator 3.

Landscapes

  • Luminescent Compositions (AREA)
  • Fats And Perfumes (AREA)
  • Spark Plugs (AREA)
EP91830415A 1990-10-12 1991-10-08 Bougie d'allumage Withdrawn EP0480886A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT6777890 1990-10-12
IT67778A IT1241643B (it) 1990-10-12 1990-10-12 Candela di accensione

Publications (1)

Publication Number Publication Date
EP0480886A1 true EP0480886A1 (fr) 1992-04-15

Family

ID=11305227

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91830415A Withdrawn EP0480886A1 (fr) 1990-10-12 1991-10-08 Bougie d'allumage

Country Status (2)

Country Link
EP (1) EP0480886A1 (fr)
IT (1) IT1241643B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0625813A1 (fr) * 1993-05-19 1994-11-23 Cooper Industries Italia S.p.A. Bougie d'allumage
DE4422939A1 (de) * 1994-06-30 1996-01-04 Bosch Gmbh Robert Zündkerze für Brennkraftmaschinen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB383600A (en) * 1931-12-23 1932-11-17 Bosch Robert Improvements in or relating to sparking plugs
GB850402A (en) * 1957-12-16 1960-10-05 Lucas Industries Ltd Sparking plugs

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB383600A (en) * 1931-12-23 1932-11-17 Bosch Robert Improvements in or relating to sparking plugs
GB850402A (en) * 1957-12-16 1960-10-05 Lucas Industries Ltd Sparking plugs

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 14, no. 70 (E-886)(4013) 8 February 1990 & JP-A-1 289 084 ( NGK SPARK PLUG CO LTD ) 21 November 1989 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0625813A1 (fr) * 1993-05-19 1994-11-23 Cooper Industries Italia S.p.A. Bougie d'allumage
DE4422939A1 (de) * 1994-06-30 1996-01-04 Bosch Gmbh Robert Zündkerze für Brennkraftmaschinen
DE4422939C2 (de) * 1994-06-30 2000-05-31 Bosch Gmbh Robert Zündkerze für eine Brennkraftmaschine

Also Published As

Publication number Publication date
IT9067778A0 (it) 1990-10-12
IT1241643B (it) 1994-01-25
IT9067778A1 (it) 1992-04-12

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19920707

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