Fouling resistant spark plugs
AssigneeFram Group IP LLC
InventorsJing ZHENG, Ronald P. Rohrbach, Peter D. UNGER, Jeffrey T. BOEHLER
Life of this patent
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Abstract
A spark plug includes an insulative sleeve. A glaze coating is disposed on an exterior surface of the insulative sleeve. The glaze coating includes a boric acid, a borosilicate glass, a barium borate glass, a phosphorous glass, a silicate glass, or a combination thereof. The glasses are independently modified with a modifier selected from the group consisting of alkali group metals, alkali earth group metals, aluminum, silicon, a halogen, or a combination thereof. The glaze coating has a softening point between about 650° C. and about 1100° C.
Claims31
A spark plug comprising
- an insulative sleeve having a central axial bore and an exterior surface, wherein a glaze coating is disposed on the exterior surface, wherein the glaze coating is a continuous band located about 0.1 to about 5 millimeters from a top edge of the insulative sleeve, the band having a width of about 1 to about 20 mm, wherein the glaze coating has a softening point between about 650° C. and about 1100° C., wherein the glaze coating is located from about 1 mm to about 3 mm away from the central axial bore, and wherein the glaze coating comprises (a) a glass material selected from the group consisting of boric acid, a borosilicate glass, a barium borate glass, a phosphorous glass, a silicate glass, and a combination thereof, and (b) a modifier selected from the group consisting of an alkali group metal, an alkali earth group metal, aluminum, silicon, a halogen, and a combination thereof;
- a center electrode extending through the central axial bore of the insulative sleeve and having a firing tip that extends beyond the top edge of the insulative sleeve;
- a metal shell, wherein the insulative sleeve is positioned within and secured to the metal shell;
- and
- a ground electrode supported by the metal shell and positioned in a spaced relationship relative to the center electrode so as to generate a spark gap.
A spark plug comprising
- an insulative sleeve having a central axial bore and an exterior surface, wherein a glaze coating is disposed on the exterior surface, wherein the glaze coating is a continuous band located about 0.1 to about 5 millimeters from a top edge of the insulative sleeve, the band having a width of about 1 to about 20 mm, wherein the glaze coating has a softening point between about 650° C. and about 1000° C., wherein the glaze coating has a thickness of about 100 to about 400 micrometers, wherein the glaze coating is located from about 1 mm to about 3 mm away from the central axial bore, and wherein the glaze coating comprises (a) a glass material selected from the group consisting of boric acid, a borosilicate glass, a barium borate glass, a phosphorous glass, a silicate glass, and a combination thereof, and (b) a modifier selected from the group consisting of alumina, silica, CaO, SrO, BaO, Na2O, MgO, Cl, and a combination thereof;
- a center electrode extending through the central axial bore of the insulative sleeve and having a firing tip that extends beyond the top edge of the insulative sleeve;
- a metal shell, wherein the insulative sleeve is positioned within and secured to the metal shell;
- and
- a ground electrode supported by the metal shell and positioned in a spaced relationship relative to the center electrode so as to generate a spark gap
A method of making a fouling resistant spark plug, the method comprising:
- providing a spark plug subassembly comprising an insulative sleeve, a center electrode, a resistor, and a terminal stud end;
- applying a dispersion to at least a portion of an exterior surface of the insulative sleeve, the dispersion comprising a glaze coating;
- and
- air-drying the dispersion, thereby forming a coated spark plug assembly;
- wherein the glaze coating has a softening point between about 650° C. and about 1100° C.;
- wherein the glaze coating comprises (a) a glass material selected from the group consisting of boric acid, a borosilicate glass, a barium borate glass, a phosphorous glass, a silicate glass, and a combination thereof, and (b) a modifier selected from the group consisting of an alkali group metal, an alkali earth group metal, aluminum, silicon, a halogen, and a combination thereof;
- wherein the glaze coating forms a continuous band located about 0.1 to about 5 millimeters from a top edge of the insulative sleeve;
- and
- wherein the band has a width of about 1 to about 20 mm.
A spark plug comprising an insulative sleeve having a glaze coating thereon, wherein the glaze coating is located from about 1 mm to about 3 mm away from a central axial bore of the spark plug, and wherein the insulative sleeve has a resistance of at least 11 Gohms at 300° C. when the insulative sleeve undergoes heat treatment at a temperature of between about 700° C. and about 1000° C.
A spark plug comprising:
- an insulative sleeve having a glaze coating thereon;
- and
- an electrode having a firing tip extending beyond the insulative sleeve;
- wherein the glaze coating is located from about 1 mm to about 3 mm away from a central axial bore of the spark plug;
- and
- wherein resistance of the glaze coating at a position below the firing tip is greater than 80 Mohms at 350° C. to 400° C.
Dependencies are inferred from the claim text.