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US3691418A - High voltage sparkplug - Google Patents

High voltage sparkplug Download PDF

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Publication number
US3691418A
US3691418A US165151A US3691418DA US3691418A US 3691418 A US3691418 A US 3691418A US 165151 A US165151 A US 165151A US 3691418D A US3691418D A US 3691418DA US 3691418 A US3691418 A US 3691418A
Authority
US
United States
Prior art keywords
sparkplug
insulator
ribs
housing
grooves
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.)
Expired - Lifetime
Application number
US165151A
Other languages
English (en)
Inventor
Otto Beesch
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.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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 Robert Bosch GmbH filed Critical Robert Bosch GmbH
Application granted granted Critical
Publication of US3691418A publication Critical patent/US3691418A/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H01T13/38—Selection of materials for insulation

Definitions

  • a high-voltage sparkplug has an electrically conductive housing from one end of which aground electrode projects.
  • An elongated center electrode extends through the housing and has a first end portion projecting from the one end and defining a spark gap with the ground electrode and a second end portion projecting from the opposite end of the housing and having a free terminal.
  • An electrical insulator insulates the center electrode from the housing and includes-an elongated insulator portion which surrounds the second end portion of the center electrode intermediate the housing and the terminal and is provided in its outer circumferential surface with a plurality of axially spaced grooves which serve to retard current leakage between the terminal and the housing by increasing the sparkover potential between the two.
  • the grooves are provided at least in that part of the insulator portion which is nearer to the free terminal and are separated from each other by ribs having flanks which make with a plane normal to the axis of the insulator an angle of about 10.
  • the present invention relates generally to spark plugs, and more particularly to high-voltage sparkplugs. It is known to construct sparkplugs in the outer circumferential surface of that portion of their insulator which is located exteriorly of the sparkplug housing, with circumferential grooves which increase the current leakage path between the center electrode and the housing which is connected to ground, to thereby reduce spark-over.
  • the conventional sparkplugs provided with such grooves are employed under conditions requiring a medium potential, under which circumstances the increas of the current-leakage path afforded by these grooves-which usually are of triangular or near-triangular cross-section--is entirely adequate.
  • a further object of the invention is to provide a sparkplug wherein the spark-over potential is substantially increased over the value know from and achievable with prior-art sparkplugs.
  • One feature of the invention resides in the provision of a high-voltage sparkplug for use in internal combustion engines which comprises a conductive housing or shell having opposite ends and a ground electrode provided at one of these ends.
  • An elongated center electrode extends through the housing and has a first end portion projecting from the one end and defining a spark gap with the ground electrode.
  • a second end portion of the elongated center electrode projects from the other end of the housing and has an exposed terminal remote from the latter.
  • An electrical insulator insulates the center electrode from the housing and includes an elongated insulator portion surrounding the second end portion intermediate the other end of the housing and the terminal.
  • the insulator portion is provided with a plurality of circumferential ribs separated from each other by annular current leakage-reducing grooves. These ribs have substantially radially extending flanks which make with respect to a plane that is normal to the axis of the insulator an angle of substantially less than 20, preferably 5-l 5 and most preferably 10.
  • FIG. 1 is an elevational view, partly in section, illustrating a sparkplug which is constructed in accordance with the present invention
  • FIG. 2 is a fragmentary sectional detail view, on an enlarged scale, of the electrical insulator of the sparkplug in FIG. 1;
  • FIG. 3 is a view similar to that of FIG. 2 but further showing the dimensions of various parts of the insulator.
  • the reference numeral 10 denotes a housing or shell which forms part of my novel sparkplug.
  • This housing 10 consists of steel. Secured to the housing 10 at one end thereof is a ground electrode 11 which is conductively connected to the housing.
  • An insulator 12 consisting of ceramic material capable of providing the requisite electrical insulation extends into the housing 10.
  • the insulator 12 is gas-tightly mounted in the housing 10. Extending through the insulator is a high-voltage electrode 13 which is gastightly mounted in the insulator 12.
  • the free or terminal end of the electrode 13 is provided with an exterior thread (no reference numeral) which meshes with corresponding interior threads provided on a cap nut 14 WHICH serves to connect to the center electrode 13 a voltage supply cable (not illustrated).
  • the cable can also be connected with the terminal end of the electrode 13 in some other manner, and it is not a part of this invention.
  • the other end of the electrode 13 defines with ground electrode 11 a spark gap.
  • each rib 16 is approximately the same as the average width of each groove 15.
  • each of the grooves 15 and ribs 16 consist of two halves which are substantially symmetrical with reference to a plane extending through the respective groove or rib in the direction normal to the axis X-X of the insulator.
  • the transition between the flanks 16a and 16b and the peripheral surfaces 16c of the ribs 16 and the surfaces 15a in the innermost regions of the grooves 15 have been smoothed. These transitions are shown in FIG. 3 with radii of curvature of 0.3 mm and 0.4 mm respectively.
  • the insulator 12 is slightly tapered. At its upper end ithas a diameter of 11.8 mm which increases to a diameter of 12.2 mm at the lowest rib.
  • the diameter of the insulator at the uppermost groove is 10.0 mm which increases to a diameter of 10.3 mm at the lowest groove.
  • the grooves are of a substantially trapezoidal cross-section. It is these grooves, and more particularly their cross-sectional configuration, which retards current leakage between the terminal 13 and the housing by increasing the spark-over potential between the two.
  • the rounded surfaces that make up the transition between the peripheral surfaces of the ribs, the flanks, and the innermost region of the grooves prevent potential peaks and discharges from these junctures as could take place if the junctures were sharp rather than rounded.
  • spark-over potential can be increased in the sparkplug according to the present invention, for example, from 27,000 volts attainable with a conventional sparkplug to 31,000 volts.
  • the grooves are (but need not be) of substantially trapezoidal crosssection and constitute a leakage-barrier which prevents spark-over between the center electrode and the sparkplug housing in the potential range in question.
  • a high-voltage sparkplug for use in internal combustion engines, comprising an electrically conductive housing having opposite ends; a ground electrode provided at one of said ends; an elongated center electrode extending through said housing and having a first end portion projecting from said one end and defining with said ground electrode a spark gap, and a second end portion projecting from the other of said ends and having a terminal remote from the latter; and an electrical insulator insulating said center electrode from said housing and including and elongated insulator portion having an outer surface and surrounding said second end portion intermediate said other end and said terminal, said insulator portion having a plurality of circumferential ribs separated from each other by annular current-leakage retarding grooves and said ribs having substantially radially extending flanks making with a plane which is normal to the-axis of said insulator an angle of substantially less than 20.
  • said elongated insulator portion includes a first part nearer to and a second part remote from said terminal, said ribs and said grooves being provided at least in said first part of said insulator portion.
  • said insulator portion further comprises annular faces disposed in said grooves between said ribs, there being a smooth transition between each of said annular faces and the adjoining flanks.
  • each of said ribs has an annular peripheral surface, there being a smooth transition between each such peripheral surface and the flanks of the respective rib.
  • flanks of each of said ribs are substantially mirror symmetrical with reference to a plane halving the respective rib and normal to said axis.

Landscapes

  • Spark Plugs (AREA)
US165151A 1969-03-18 1971-07-22 High voltage sparkplug Expired - Lifetime US3691418A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1913582A DE1913582C3 (de) 1969-03-18 1969-03-18 Zündkerze zum Betrieb von Brennkraftmaschinen

Publications (1)

Publication Number Publication Date
US3691418A true US3691418A (en) 1972-09-12

Family

ID=5728438

Family Applications (1)

Application Number Title Priority Date Filing Date
US165151A Expired - Lifetime US3691418A (en) 1969-03-18 1971-07-22 High voltage sparkplug

Country Status (6)

Country Link
US (1) US3691418A (es)
JP (1) JPS4844702B1 (es)
DE (1) DE1913582C3 (es)
ES (1) ES156885Y (es)
FR (1) FR2039027A5 (es)
GB (1) GB1260455A (es)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2418971A1 (fr) * 1978-03-01 1979-09-28 Scamea Bougie d'allumage perfectionnee

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2418971A1 (fr) * 1978-03-01 1979-09-28 Scamea Bougie d'allumage perfectionnee

Also Published As

Publication number Publication date
DE1913582C3 (de) 1975-07-17
ES156885U (es) 1970-05-16
ES156885Y (es) 1971-02-01
DE1913582A1 (de) 1970-09-17
GB1260455A (en) 1972-01-19
FR2039027A5 (es) 1971-01-08
DE1913582B2 (de) 1974-12-05
JPS4844702B1 (es) 1973-12-26

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