US3488556A - Spark plug with main and teaser gaps in parallel - Google Patents

Spark plug with main and teaser gaps in parallel Download PDF

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Publication number
US3488556A
US3488556A US687203A US3488556DA US3488556A US 3488556 A US3488556 A US 3488556A US 687203 A US687203 A US 687203A US 3488556D A US3488556D A US 3488556DA US 3488556 A US3488556 A US 3488556A
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United States
Prior art keywords
electrode
gap
spark plug
main
insulator
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Expired - Lifetime
Application number
US687203A
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English (en)
Inventor
Harvey A Burley
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.)
Motors Liquidation Co
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Motors Liquidation Co
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Filing date
Publication date
Application filed by Motors Liquidation Co filed Critical Motors Liquidation Co
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Publication of US3488556A publication Critical patent/US3488556A/en
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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
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/34—Sparking plugs characterised by features of the electrodes or insulation characterised by the mounting of electrodes in insulation, e.g. by embedding

Definitions

  • This invention relates to spark plugs, and more particularly to three electrode spark plugs.
  • a three electrode spark plug having two spark gaps.
  • a small or trigger gap is formed between the center electrode and the third electrode.
  • a resistor is connected in series with the third electrode so that voltage impressed upon the spark plug causes arcing across the trigger gap which continues for a time sufficient to ionize the gaseous molecules in the main gap region thereby reducing the breakdown voltage of the main gap, that is, the voltage-required to initiate sparking across the main gap between the center electrode and the ground electrode.
  • a voltage of about kv. is required at a pressure of 120 pounds per square inch with this three electrode spark plug compared to a voltage of 18 to 20 kv. with a conventional spark plug at the same pressure.
  • This spark plug has reduced electrical insulation problems and substantially reduced radio frequency interference.
  • FIGURE 1 is a side view of an improved three electrode spark plug
  • FIGURE 2 is an enlarged view of the firing tip portion of a second embodiment of an improved three electrode spark plug
  • FIGURE 3 is an enlarged view of the firing tip portion 3,488,556 Patented Jan. 6, 1970 of a third embodiment of an improved three electrode spark plug;
  • FIGURE 4 indicates the effect of the resistor size on the spark plug breakdown mode
  • FIGURE 5 indicates the difference in breakdown voltage between a conventional spark plug and the improved three electrode spark plug.
  • FIGURE 1 of the spark plug 10 comprises a conventional outer metal shell 12 having a ground electrode 14 Welded to the lower end thereof. Positioned within the metal shell 12 and secured in the conventional manner is the insulator 16.
  • the insulator 16 should preferably be of a high alumina base material containing upwards of aluminum oxide such, for example, as covered by United States Patent No. 2,760,877, issued to Karl Schwartzwalder and Helen Blair Barlett.
  • the insulator 16 is formed with a stepped centerbore 18 having a shoulder 19.
  • a tubular third electrode 20 Positioned within the insulator ceuterbore 18 is a tubular third electrode 20 having a flared upper portion 22 supported by the insulator shoulder 19. Positioned within the tubular third electrode 20 is a tubular insulator 24 having an upper flared end portion 26.
  • the insulator 24 should preferably be of a high alumina base material containing upwards of 85% aluminum oxide of the type described previously for the insulator 16.
  • Positioned within the tubular insulator 24 Positioned within the tubular insulator 24 is the center electrode 28.
  • the insulator 24 electrically insulates the center electrode 28 from the third electrode 20.
  • a glass mass 30 hermetically seals the center electrode 28 to the insulator flared portion 26, the third electrode flared end 22. and the insulator 16.
  • the lower end 32 of the tubular insulator 24 is preferably flush with the center electrode firing tip end 34 and the third electrode firing tip end 36.
  • the center electrode firing tip end 34 and the third electrode firing tip end 36 form a small or trigger gap therebetween.
  • the length of the trigger gap existing between the third electrode and the center electrode is from about 0.001 inch to 0.020 inch with the preferred length being 0.003 to 0.010 inch.
  • the length of the trigger gap is usually selected on the basis of performance under adverse conditions such as fouling, flood start, and cold start.
  • a resistor 38 is located in insulator 16 and connected in series between the outer shell 12 and. the tubular third electrode 20. While the resistor may he in the form of a unitary body which is connected by leads to the shell and the center electrode, the resistor may take the form of a solid body which in itself makes electrical contact with the third electrode 20 and the shell 12. As shown in FIGURE 2, the resistor 38A is a solid mass passing through a hole or opening 39 in the insulator 16 and is in electrical contact with the third electrode and the shell. As shown in FIGURE 3, the resistor may take form of an annular button 38B having a centerbore 41 which encircles and is in contact with the tubular third electrode 20 and an outer surface which is in contact with the shell.
  • the resistor 38 may be positioned outside of the spark plug 10 as long as the resistor is connected in series with the third electrode 20 and is also connected to a ground.
  • the position of the resistor is not critical in the practice of this invention.
  • the resistor 38 should have a resistance in the order of 10 ohms to be Operative under the pressure conditions most commonly encountered in automotive application. As can be seen in FIGURE 4, if the resistance of the resistor 38 is too low, only the trigger gap fires whereas resistances above ohms will operate both the trigger gap and the main gap under all conditions including the extreme high pressure conditions of about 120 p.s.i.
  • the center electrode firing tip portion and the firing tip end portion of ground electrode 14 form the conventional spark plug main gap.
  • the main gap is about 0.035 inch in length.
  • the length of the main gap depends upon the particular engine in which it is used. As it is well known in the art, a small gap is more efficient for igniting good fuelair mixtures whereas a large gap is more efiicient for igniting lean mixtures and rich mixtures.
  • the three electrode spark plug described above is connected in an ignition system which is a modification of the conventional inductive ignition system.
  • the conventional inductive system containing a coil having a 100 to 1 turn ratio and delivering up to 28 kv. is modified by using a coil having a 30 to 1 turn ratio which in turn delivers about 8 kv.
  • the ignition system delivers the voltage to the spark plug initiating arcing across the small or trigger gap which continues for a time sufficient to ionize some of the gas in the main gap.
  • the ionization of the gas in the main gap reduces the voltage required to cause a spark to jump across the main gap.
  • the three electrode spark plug of this invention will, due to the ionization of gas in the main gap caused by the arcing in the trigger gap, spark across the main gap with a voltage ranging from 2 to 6 or 7 kv. depending upon the operating conditions and the pressure in the combustion chamber.
  • the breakdown voltage required for a spark to jump across the 0.008 inch trigger gap was found to be 8 kv.
  • the voltage dropped momentarily to 3 kv. and then started to rise with the trigger current continuing to flow.
  • sparking across the 0.035 inch main gap commenced.
  • that is pressure in the range of 100 to 120 p.s.i. even the trigger spark by itself is sufiicient to ignite the fuel-air mixture.
  • a trigger gap lowers the breakdown voltage of the main gap significantly depending upon the pressure at which the sparking occurs.
  • a conventional spark plug having a main gap of 0.035 inch has a breakdown voltage at 120 p.s.i. of about 20 kv. whereas the improved three electrode spark plug having the same size main gap and a trigger gap of 0.010 inch is 5 kv.
  • the breakdown voltage of the trigger gap spark plug is affected to a lesser degree by the pressure than the conventional spark plug in respect to the breakdown voltage.
  • the three electrode spark plug of this invention permits the use of a lower voltage in obtaining sparking across the main gap. Since the breakdown voltage is considerably less than in the conventional spark plug, the radio frequency interference is significantly reduced.
  • a spark plug comprising a metal shell having a ground electrode secured to one end thereof, an insulator having a centerbore therethrough secured within said shell, a center electrode positioned in one end of said centerbore and having an end portion extending through said insulator into spaced relationship with said ground electrode to form a first spark gap therebetween, a third electrode positioned in spaced relationship with said center electrode and having an end portion adapted to form a second spark gap with said center electrode and a resistor connected in series with said third electrode wherein a voltage impressed upon said spark plug initiates arcing in said second gap which continues for a time sufiicient to ionize gas in said first gap thereby reducing the voltage required to initiate sparking in said first gap.
  • a spark plug comprising a metal shell having a ground electrode secured to one end thereof, a first insulator having a centerbore therethrough secured within said shell, a tubular third electrode positioned within said first insulator centerbore, a second tubular insulator having a centerbore therethrough positioned in said tubular third electrode, a center electrode positioned in said tubular insulator centerbore and having an end portion extending through said first insulator into spaced relationship with said ground electrode to form a first spark gap therebetween, said third electrode having an end portion adapted to form a second spark gap with said center electrode and a resistor connected in sereis with said third electrode wherein a voltage impressed upon said spark plug initiates arcing in said second gap which continues for a time sufiicient to ionize gas in said first gap thereby reducing the voltage required to initiate sparking in said first gap.
  • a spark plug comprising a metal shell having a ground electrode secured to one end thereof, an insulator having a centerbore therethrough secured within said shell, a center electrode positioned in one end of said centerbore and having an end portion extending through said insulator into spaced relationship with said ground electrode to form a first gap therebetween, a third electrode positioned in spaced relationship with said center electrode and having an end portion adapted to form a second gap with said center electrode and a resistor body in electrical contact with said third electrode and said metal shell wherein a voltage impressed upon said spark plug initiates arcing in said second gap which continues for a time sufficient to ionize gases in said first gap thereby reducing the voltage required to initiate sparking in said first gap.

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  • Spark Plugs (AREA)
US687203A 1967-12-01 1967-12-01 Spark plug with main and teaser gaps in parallel Expired - Lifetime US3488556A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US68720367A 1967-12-01 1967-12-01

Publications (1)

Publication Number Publication Date
US3488556A true US3488556A (en) 1970-01-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
US687203A Expired - Lifetime US3488556A (en) 1967-12-01 1967-12-01 Spark plug with main and teaser gaps in parallel

Country Status (5)

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US (1) US3488556A (de)
BR (1) BR6804136D0 (de)
DE (1) DE1811110A1 (de)
FR (1) FR1596735A (de)
GB (1) GB1176440A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890518A (en) * 1972-06-01 1975-06-17 Lucas Industries Ltd Spark ignition plug
US3890519A (en) * 1972-06-08 1975-06-17 Lucas Industries Ltd Spark discharge plugs
US4004562A (en) * 1974-12-26 1977-01-25 Ford Motor Company Multiple air gap spark plug having resistive electrode coupling
US4219001A (en) * 1976-09-30 1980-08-26 Tokai Trw & Co. Ltd. Method and apparatus for accumulating fuel particles in a portion of a combustion chamber
US20050057132A1 (en) * 2003-09-15 2005-03-17 Cleeves James M. Spark plug
US20130192571A1 (en) * 2012-01-27 2013-08-01 Mitsubishi Electric Corporation Ignition apparatus

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1290780A (en) * 1917-06-07 1919-01-07 Albert A Radtke Spark-plug.
US1399166A (en) * 1919-03-07 1921-12-06 Springer Franklin Wesley Spark-plug for internal-combustion engines
US2963620A (en) * 1959-08-27 1960-12-06 Gen Lab Associates Inc Sensing igniter
US3049644A (en) * 1960-05-02 1962-08-14 Chrysler Corp Ignition system
US3146301A (en) * 1958-04-21 1964-08-25 Bendix Corp Spark discharge device
US3344304A (en) * 1965-06-23 1967-09-26 Gen Motors Corp Creepage spark type plug having low voltage igniter seal

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1290780A (en) * 1917-06-07 1919-01-07 Albert A Radtke Spark-plug.
US1399166A (en) * 1919-03-07 1921-12-06 Springer Franklin Wesley Spark-plug for internal-combustion engines
US3146301A (en) * 1958-04-21 1964-08-25 Bendix Corp Spark discharge device
US2963620A (en) * 1959-08-27 1960-12-06 Gen Lab Associates Inc Sensing igniter
US3049644A (en) * 1960-05-02 1962-08-14 Chrysler Corp Ignition system
US3344304A (en) * 1965-06-23 1967-09-26 Gen Motors Corp Creepage spark type plug having low voltage igniter seal

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890518A (en) * 1972-06-01 1975-06-17 Lucas Industries Ltd Spark ignition plug
US3890519A (en) * 1972-06-08 1975-06-17 Lucas Industries Ltd Spark discharge plugs
US4004562A (en) * 1974-12-26 1977-01-25 Ford Motor Company Multiple air gap spark plug having resistive electrode coupling
US4219001A (en) * 1976-09-30 1980-08-26 Tokai Trw & Co. Ltd. Method and apparatus for accumulating fuel particles in a portion of a combustion chamber
US20050057132A1 (en) * 2003-09-15 2005-03-17 Cleeves James M. Spark plug
US7098581B2 (en) 2003-09-15 2006-08-29 Cleeves James M Spark plug
US20060232276A1 (en) * 2003-09-15 2006-10-19 Cleeves James M Spark plug
US7309951B2 (en) 2003-09-15 2007-12-18 Cleeves James M Spark plug
US20130192571A1 (en) * 2012-01-27 2013-08-01 Mitsubishi Electric Corporation Ignition apparatus
US9212646B2 (en) * 2012-01-27 2015-12-15 Mitsubishi Electric Corporation Ignition apparatus

Also Published As

Publication number Publication date
FR1596735A (de) 1970-06-22
DE1811110B2 (de) 1970-08-13
DE1811110A1 (de) 1969-08-07
GB1176440A (en) 1970-01-01
BR6804136D0 (pt) 1973-01-11

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