# US 2019/0214794 A1 · Fouling resistant spark plugs > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0214794 A1 - Document ID: US20190214794A1 - Status: Published application - Kind: A1 - Application number: 15/863,427 - Filed: 2018-01-05 - Published: 2019-07-11 - Earliest claimed: 2018-01-05 - Assignees: Fram Group IP LLC - Applicants: Fram Group IP LLC - Inventors: Jing ZHENG; Ronald P. Rohrbach; Peter D. UNGER; Jeffrey T. BOEHLER - Web page: https://patentgrep.com/patent/US20190214794A1 ## CPC - H01T 13/38: Selection of materials for insulation - H01T 21/02: of sparking plugs - H01T 13/14: Means for self-cleaning - H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H) ## 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. ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The spark plug of claim 1 wherein the modifier is selected from the group consisting of an alkali group metal oxide, an alkali earth group metal oxide, alumina, silica, a chloride, and a combination thereof. ### Claim 3 (depends on 1) The spark plug of claim 1 wherein the modifier is selected from the group consisting of alumina, silica, CaO, SrO, BaO, Na2O, MgO, Cl, and a combination thereof. ### Claim 4 (depends on 1) The spark plug of claim 1 wherein the glaze coating further comprises an inorganic filler. ### Claim 5 (depends on 4) The spark plug of claim 4 wherein the inorganic filler is selected from the group consisting of fumed silica, hydrophilic fumed silica, wollastonite, and a combination thereof. ### Claim 6 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a softening point of between about 650 and about 1050° C. ### Claim 7 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a softening point of between about 650 and about 1000° C. ### Claim 8 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a softening point of between about 650 and about 950° C. ### Claim 9 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a thickness of about 1 to about 500 micrometers. ### Claim 10 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a thickness of about 100 to about 400 micrometers. ### Claim 11 (depends on 1) The spark plug of claim 1, wherein the glaze coating has a thickness of about 300 to about 400 micrometers. ### Claim 12 (depends on 1) The spark plug of claim 1, wherein the insulative sleeve has a resistivity of greater than or equal to about 1×106 ohms/mm prior to use in an engine. ### Claim 13 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 ### Claim 14 (depends on 13) The spark plug of claim 13, wherein the glaze coating has a glass transition temperature about 700° C. and about 1000° C. ### Claim 15 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. ### Claim 16 (depends on 15) The method of claim 15 wherein the dispersion comprises a carrier selected from the group consisting of water, alcohol, mineral spirits, acetone, and a combination thereof. ### Claim 17 (depends on 15) The method of claim 15 wherein the applying of the dispersion comprises painting, dip coating, spray coating, or a combination thereof. ### Claim 18 (depends on 15) The method of claim 15 wherein the air-drying occurs under an optional air flow. ### Claim 19 (depends on 15) The method of claim 15 wherein the air-drying occurs at room temperature for a period of time ranging from about 1 to about 4 hours. ### Claim 20 (depends on 19) The method of claim 19 further comprising heating the coated spark plug assembly at a temperature ranging from about 650 to about 1100° C. for a period of time from about 20 minutes to about 5 hours. ### Claim 21 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. ### Claim 22 (depends on 21) The spark plug of claim 21 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. ### Claim 23 (depends on 21) The spark plug of claim 21, wherein the glaze coating has a softening point of between about 650 and about 1050° C. ### Claim 24 (depends on 21) The spark plug of claim 21, wherein the glaze coating has a softening point of between about 650 and about 1000° C. ### Claim 25 (depends on 21) The spark plug of claim 21, wherein the glaze coating has a thickness of about 1 to about 500 micrometers. ### Claim 26 (depends on 21) The spark plug of claim 21, wherein the glaze coating has a thickness of about 100 to about 400 micrometers. ### Claim 27 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. ### Claim 28 (depends on 27) The spark plug of claim 27 wherein the resistance of the glaze coating at a position below the firing tip is greater than 200 Mohms at 350° C. to 400° C. ### Claim 29 (depends on 27) The spark plug of claim 27 wherein the resistance of the glaze coating at a position below the firing tip is greater than 300 Mohms at 350° C. to 400° C. ### Claim 30 (depends on 27) The spark plug of claim 27 wherein the resistance of the glaze coating at a position below the firing tip is greater than 400 Mohms at 350° C. to 400° C. ### Claim 31 (depends on 27) The spark plug of claim 27 wherein the resistance of the glaze coating at a position below the firing tip is greater than 500 Mohms at 350° C. to 400° C.