US3522465A - Slide-spark electrode system - Google Patents

Slide-spark electrode system Download PDF

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Publication number
US3522465A
US3522465A US708990A US3522465DA US3522465A US 3522465 A US3522465 A US 3522465A US 708990 A US708990 A US 708990A US 3522465D A US3522465D A US 3522465DA US 3522465 A US3522465 A US 3522465A
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US
United States
Prior art keywords
slide
electrodes
silicon carbide
spark
electrode system
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Expired - Lifetime
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US708990A
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English (en)
Inventor
Wilhelmus Francisc Knippenberg
Gregorius Thedorus Mari Neelen
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US Philips Corp
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US Philips Corp
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Publication date
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    • 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
    • H01T13/52—Sparking plugs characterised by a discharge along a surface

Definitions

  • the slide-spark type spark plug has the space between the electrodes filled with a semiconductive material which allow a chain of small sparks across the surface.
  • the semiconductive material is silicon carbide with the surface doped to permit current to flow.
  • This invention relates to slide-spark electrode systems, more particularly slide-spark plugs.
  • slide-spark electrode system is to be understood in this specification to mean a device having electrodes which are separated by an insulating or semiconductor body, wherein a slide spark can be produced across the surface of the separating body by applying a voltage between the electrodes, for example, by means of a capacitor discharge.
  • the electrodes may be arranged with some spacing between them or one electrode may co-axially surround the other. It is also possible that more than two electrodes are present.
  • the device above referred to affords the advantage of operating at lower voltages. Furthermore they are much less sensitive to contamination such as may occur, for example, in uses where liquid fuels are employed in the form of fuel drops or from which carbon deposits may be formed in operation.
  • a device of this kind having an insulating separating body between the electrodes is known, for example, from Dutch Pat. No. 46,114.
  • this device use is made of the fact that deposition of fuel drops and soot on the insulating separating body makes the formation of slide sparks possible.
  • separating bodies have the disadvantage of being not particularly resistant against the action of the sparks.
  • the separating bodies of heat-proof and chemically resistant materials, such as silicon carbide and boron carbide.
  • German Pat. No. 898,325 for this purpose the separating body is formed of said substances, possibly with an addition of ceramic materials and carbon, and exposed to temperatures of 1500 C. for comparatively a long period.
  • the resulting high-ohmic sintered product is then covered by vapour deposition within a thin metal layer. A radical solution is thus not obtained. If the resistance of the body is very high, the regular occurrence of slide sparks is ensured only if a metal layer has been applied.
  • this metal layer is not particularly durable in operation.
  • the material forming the separating body has so low a resistance that slide sparks can be obtained, an additional insulation of the electrodes will be necessary as has been described in Dutch Pat. No. 90,047.
  • An object of the invention is to obviate the described disadvantages inherent in known devices.
  • the present invention relates to a slide-spark electrode system, more particularly a slide-spark plug, which has a separating body between the electrodes, and it is characterized in that the separating body consists of compact pure high-ohmic silicon carbide, one surface layer of which has been made conductive, possibly in a given pattern, by diffusion of donors or acceptors in such manner that for a given distance between the electrodes a slidespark discharge between the electrodes may be established through the said surface layer.
  • Such a separating body not only has a high resistivity to slide-spark discharge so that a long life-length is ensured, but also any additional insulation of the electrodes for preventing leakage currents can be omitted.
  • a kind of conduction of the surface layer is brought about which varies little with temperature, in order that the resistance in operation does not become so high or so low that a slide-spark discharge is made impossible.
  • a surface layer having a weakly positive temperature coefficient of the resistance may be obtained by diffusing nitrogen into, whereas a layer hav ing an acceptable negative temperature coefiicient is obtained by diffusion with boron or aluminum in a small dosage.
  • the separating body may comprise a piece of mono crystalline pure silicon carbide which, as is well-known, may be obtained, for example, by condensation and/or crystallisation in a space bounded by SiC in an inert atmosphere, by crystallisation from a solution in chromium, or the like. Sintered bodies of such pure silicon carbide can be used as well.
  • a very compact polycrystalline silicon carbide of high resistivity may further be obtained by pyrolytic deposition from vapour of compounds containing silicon and carbon on a carbon core, possibly in an atmosphere of hydrogen.
  • This silicon carbide for the separating body is preferred in the invention, since it can readily be obtained and at low cost.
  • the electrodes should make good electric contact with
  • an acceptor for example boron or aluminum
  • Such a step is not necessary for n-conductive surface layers such as obtained, for example, by diffusion of nitrogen.
  • FIG. 1 is a diagrammatic view, in elevation and in part section, of one embodiment of a spark plug according to the invention.
  • Two co-axial electrodes are separated by a body 3 of high-ohmic silicon carbide.
  • a surface layer 4 of the body 3 has been made conductive by diffusion of substances acting as acceptors or donors.
  • the layer 4 is in electric contact with the electrodes 2 and 3 through alloyed layers 5 of a gold-tantalum alloy.
  • pure silicon carbide For the separating body use may be made of large plate-shaped crystals of pure silicon carbide, such as may be obtained by the method described in U.S. Pat. 2,854,- 364. In this method pure crystals of silicon carbide each having a surface area of 1 sq. cm. and a thickness of 1 mm. may be obtained within 5 hours by recrystallisation and/or condensation in an atmosphere of argon in a space bounded by silicon carbide at a temperature of approximately 2500 C.
  • FIG. 2 shows a graphite cylinder 6 in which a cylinder 7 obtained by sintering pure powdered silicon carbide is placed.
  • the silicon carbide may be manufactured by pyrolysis of methylchlorosilane (SiHCl CH in hydrogen.
  • the cylinder is closed at its ends by graphite plates 8.
  • the Whole is placed in a quartz envelope 9 in which an atmosphere of argon is maintained.
  • an inductance coil 10 there is heated to 2450 C., during Which process the plate-shaped pure siliconcarbide crystals are deposited approximately at right angles to the wall of the cylinder.
  • the conductive surface 14 of each crystal is provided with ohmic contacts by alloying on it layers 16 consisting of an alloy of gold with 5% by weight of tantalum and 5% by weight of aluminum, as shown in section in FIG. 4.
  • the resulting crystals may be used as separating bodies for two juxtaposed electrodes of a slide-spark plug.
  • a silicon-carbide cavity as shown in FIG. 2 is covered by a graphite plate and a temperature of 2600' C. is maintained in it, then only few crystals are formed on the wall but a thick layer of compact pure hexagonal silicon carbide is deposited on the graphite plate.
  • This coarse polycrystalline plate is made n-conductive at its surface by heating for two hours at 2500 C. in an atmosphere of nitrogen. By removing the graphite substrate and then sawing into small blocks it is possible to obtain separating bodies for slide-spark plugs. Contacts can in this case be formed, if desired, by allowing on said bodies an alloy of gold with 5% by weight of tantalum.
  • Compact cylindrical separating bodies for slide-spark plugs having co-axial electrodes as shown in FIG. 1 may be manufactured, for example, as follows:
  • a carbon rod of 3 mm. in diameter and a length of 30 cm. is heated by passage of current at a temperature of 1500 C. in a flow of very pure hydrogen containing 2% of methylchlorosilane. If the gas fiow is led through at a rate of 5 litres/min. a compact layer of pure polycrystalline silicon carbide of 1.5 mm. thick is deposited on the carbon rod within 2. hours. Cylindrical parts of silicon carbide are obtained by dividing the rod into pieces of 5 mm. each and removing the carbon core by burning. In the manner as has been described with reference to FIG.
  • the surface at one of the end faces is made conductive by diffusion of boron, whereafter the conductive surface is provided with contacts on the inner and outer sides of the cylinder by alloying on it an alloy of gold with 5% by weight of tantalum and 5% by weight of aluminum.
  • a slide-spark electrode system comprising electrodes and a separating body between the electrodes, said separating body having a spark surface layer along Which a slide-spark discharge may be established when a voltage is applied across said electrodes, said separating body consisting essentially of compact pure high-resistivity silicon carbide having a conductive surface layer due to the presence in a surface layer of the silicon carbide of diffused donors or acceptors in a concentration gradient diminishing from the surface into the body, and means effecting electrical connection between the electrodes and the conductive surface layer.
  • silicon carbide obtained by pyrolytic vapor deposition from siliconand carbon-containing compounds onto a carbon core.

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  • Spark Plugs (AREA)
US708990A 1967-03-18 1968-02-28 Slide-spark electrode system Expired - Lifetime US3522465A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6704095A NL6704095A (en:Method) 1967-03-18 1967-03-18

Publications (1)

Publication Number Publication Date
US3522465A true US3522465A (en) 1970-08-04

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US708990A Expired - Lifetime US3522465A (en) 1967-03-18 1968-02-28 Slide-spark electrode system

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US (1) US3522465A (en:Method)
BE (1) BE712371A (en:Method)
CH (1) CH477772A (en:Method)
DE (1) DE1601432C3 (en:Method)
FR (1) FR1559333A (en:Method)
GB (1) GB1159904A (en:Method)
NL (1) NL6704095A (en:Method)
SE (1) SE332913B (en:Method)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6531809B1 (en) * 1999-02-12 2003-03-11 Robert Bosch Gmbh Spark plug having ground electrode and intermediate electrode separated by insulating body
US20070188063A1 (en) * 2006-02-13 2007-08-16 Lykowski James D Metallic insulator coating for high capacity spark plug
US20070188064A1 (en) * 2006-02-13 2007-08-16 Federal-Mogul World Wide, Inc. Metallic insulator coating for high capacity spark plug

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3500189C2 (de) * 1985-01-04 1993-12-23 Beru Werk Ruprecht Gmbh Co A Gleitfunkenzündvorrichtung

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2684665A (en) * 1949-06-09 1954-07-27 Bendix Aviat Corp Electrical apparatus
US2831138A (en) * 1955-02-03 1958-04-15 Champion Spark Plug Co Electrical connection for high energy igniters, and method for producing same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2684665A (en) * 1949-06-09 1954-07-27 Bendix Aviat Corp Electrical apparatus
US2831138A (en) * 1955-02-03 1958-04-15 Champion Spark Plug Co Electrical connection for high energy igniters, and method for producing same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6531809B1 (en) * 1999-02-12 2003-03-11 Robert Bosch Gmbh Spark plug having ground electrode and intermediate electrode separated by insulating body
US20070188063A1 (en) * 2006-02-13 2007-08-16 Lykowski James D Metallic insulator coating for high capacity spark plug
US20070188064A1 (en) * 2006-02-13 2007-08-16 Federal-Mogul World Wide, Inc. Metallic insulator coating for high capacity spark plug
US8278808B2 (en) 2006-02-13 2012-10-02 Federal-Mogul Worldwide, Inc. Metallic insulator coating for high capacity spark plug
US9490609B2 (en) 2006-02-13 2016-11-08 Federal-Mogul Worldwide, Inc. Metallic insulator coating for high capacity spark plug

Also Published As

Publication number Publication date
DE1601432C3 (de) 1978-11-02
CH477772A (de) 1969-08-31
FR1559333A (en:Method) 1969-03-07
SE332913B (en:Method) 1971-02-22
GB1159904A (en) 1969-07-30
DE1601432A1 (de) 1970-12-17
NL6704095A (en:Method) 1968-09-19
DE1601432B2 (de) 1978-03-09
BE712371A (en:Method) 1968-09-18

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