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
  • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
  • H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs
• • 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
  • H01T13/40—Sparking plugs structurally combined with other devices
  • H01T13/41—Sparking plugs structurally combined with other devices with interference suppressing or shielding means

Definitions

• the subject matter disclosed herein relates to a spark plug and in particular to a spark plug having a resistor made with glass materials with an increased glass transition temperature.
• Spark plugs are widely used to ignite fuel in internal combustion engines. Spark plugs are subject to intense heat in a highly corrosive environment of a vehicle engine. As a result, a spark plug having high durability and useful life is desireable. Further, in addition to igniting fuel, in some applications the spark plug is influencing the senor signal acquired by the vehicle control system to monitor the operation of the engine. These applications typically require tighter electrical tolerances and lower electromagnetic interference (EMI) to reduce interference with signals from both the spark plug itself and the surrounding control circuitry.
• EMI electromagnetic interference
• a spark plug having a resistor made from a mixture of alkali free barium alumino-silicate glass and mullite.
• a spark plug having an insulator having an inner bore.
• a center electrode extends from one end of the inner bore.
• An insert extends from an opposite side of the inner bore.
• a resistor is disposed between the center electrode and the insert, the resistor being made from a mixture of alkali free barium alumino-silicate glass and mullite.
• a method of fabricating a sparkplug includes mixing carbon and ceramic powder to make carbon slurry.
• the carbon slurry is added to a glass mixture containing an alkali free barium borate glass and Mullite.
• the carbon slurry-glass mixture is dried and then screened to form a carbon resistor glass.
• the carbon resistor glass is loaded into a sparkplug insulator.
• the sparkplug insulator-carbon glass assembly is heated to transform the carbon resistor glass into a semi-melt condition.
• FIG. 1 is a side sectional view of a spark plug in accordance with an embodiment of the invention.
• FIG. 2 is a graph showing the results of a spark plug resistance test based on controlled kiln temperature
• FIG. 3 is a graph showing the results of a spark plug accumulated failure rate under accelerated testing
• FIG. 4 is a graph showing the results of a spark plug resistance change based on production kiln temperature.
• FIG. 5 is a flow chart showing a method of fabricating a spark plug in accordance with an embodiment of the invention.
• Embodiments of the present invention provide advantages in reducing the variation of resistance values for a resistor in a spark plug application. It has been found that the resistor glass materials are sensitive to kiln process temperature. This temperature sensitivity leads to a variation in resistance during the spark plug assembly process. Embodiments of the present invention provide for a resistor material that has an improved durability, a longer useful life and may be processed at a wider range of processing temperatures while maintaining a low variation in resistance. Embodiments of the present invention further provide for a smaller electromagnetic interference range for spark plugs.
• the spark plug 20 includes a metal casing or shell 22 having an externally threaded cylindrical base 24 for threadable engagement in the cylinder head of an internal combustion engine (not shown).
• the shell may include a generally hexagonal boss 30 thereon to allow for grasping and turning of the spark plug 20 with a suitable tool, such as a conventional spark plug socket for example.
• a bi-metallic ground electrode 26 is coupled, such as by welding for example, to a lower surface 28 of the threaded base 24.
• the spark plug 20 further includes a ceramic insulator 32 disposed concentrically within the shell 22.
• a center electrode 34 is disposed concentrically within the insulator 32.
• the center electrode 34 may include a central core 36 made from a thermally conductive material, such as copper or a copper alloy for example.
• An electrode tip 38 is disposed on one end of the center electrode 34. Opposite the electrode tip 38 is an electrically conductive insert or rod 40. The insert 40 fits into the upper end of the insulator 32 and forms
• the resistor 42 Disposed between the insert 38 and the center electrode 32 is an internal resistor 42.
• the resistor material and assembly process influence resistance value of the internal resistor 42, the durability, useful life and EMI emissions of the spark plug 20.
• the resistor 42 is formed from a mixture of an alkali free barium alumino- silicate glass, Mullite, carbon, ceramic powders and other ingredients.
• the glass is composed of MgO 2.0wt% - A1203 11.3wt - Si02 53.5wt - CaO -12.0wt% - BaO - 20.5wt in composition.
• the mixture has 15-30 wt glass and 10-25% Mullite and the balance is ceramic powder, carbon, borate glass and organic binders.
• resistor glass containing the alkali free barium alumino-silicate glass first all the components, glasses, Mullite and other materials, are weighed and a carbon slurry, containing carbon and ceramic powders (Zr02) is added. The components are mixed for a predetermined amount of time. In the exemplary embodiment the components are mixed for seven minutes. Ice is added to components and further mixed for a predetermined amount of time, such as 10 minutes for example. After the components and ice are mixed, the mixture is oven dried. In the exemplary embodiment, the mixture is oven dried for 5 hours at 120C. Following the drying, the mixture is screened, such as with a #20 mesh for example. The material processed through the screen is ready to be used for assembling resistor for sparkplugs
• Fig. 2 shows the low voltage resistance of the resistor 42 at different kiln processing temperatures.
• the standard glass formulation indicated by line 44 shows a substantial variation in resistance of 54% over a processing temperature range of 200 degrees.
• the exemplary alkali free barium alumino-silicate glass/mullite resistor 42, indicated by line 46 had only a 2% variation over the same temperature range. It should be appreciated that this reduction in variation in resistance results in larger production yields.
• Current production processes have a target kiln temperature of 1775°F and the temperature is controlled within + 50°F in order to achieve a desired resistance value from the resistor 42.
• Fig. 3 shows a life curves from accelerated life tests for the exemplary alkali free barium alumino-silicate glass/mullite resistor 42 and standard spark plug resistors (as a comparison) when processed at elevated temperature of 1900F.
• the accelerated life tests were conducted in a heated pressure bomb at engine cylinder pressure.
• the standard spark plug resistor had initial failures being at six hours.
• the exemplary akili free barium alumino- silicate glass/mullite resistor 42 in contrast had no failures over a twenty-four hour period.
• the results suggest that the resistor materials containing alkali free barium alumino-slicate glass and Mullite has a wider process window to yield products with improved performance and/or longer useful life.
• Fig. 4 shows a resistance change curve for another embodiment alkali free barium alumino-silicate glass/mullite resistor 42 and a standard spark plug resistor (as a comparison), processed on standard production kiln.
• the alkali free barium alumino-silicate glass/mullite resistor 42 shows a lower resistor variation in temperature ranges lower than 1800°F, and has a processing window with a substantially flat resistance between 1750°F to 1800°F.
• a method 50 of fabricating a spark plug such as spark plug 20 for example is shown.
• the method 50 starts in block 52 where carbon and ceramic powder are mixed to make carbon slurry.
• the carbon slurry is added to the glass mixture and Mullite in block 54.
• the glass mixture includes but is not limited to alkali free barium borate glass.
• the alkali free barium borate glass may be composed of MgO 2.0wt% - A1203 11.3wt - Si02 53.5wt - CaO -12.0wt% - BaO - 20.5wt in composition.
• the mixture has 15-30 wt glass and 10-25% Mullite and the balance is ceramic powder, carbon, borate glass and organic binders.
• the mixture is then dried and screened in block 56 to form a carbon resistor glass.
• the desired volume of carbon resistor glass is then loaded into sparkplug insulators, such as insulator 32 for example, in block 58.
• the above insulator glass assembly is then subject to high temperature environment in block 60.
• the insulator-glass assembly is carried on a conveyor through an oven operating at a temperature of 1650F to 1850F.
• a plunge terminal stud
• the glass powders in semi-melt condition
• the resistor is hence formed and sealed into the sparkplugs.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Spark Plugs (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Glass Compositions (AREA)

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• 2012
  • 2012-04-11 US US13/444,098 patent/US8963406B2/en active Active
  • 2012-04-12 WO PCT/US2012/033177 patent/WO2012166248A1/en not_active Ceased
  • 2012-04-12 DE DE112012002353.6T patent/DE112012002353T5/de not_active Withdrawn
  • 2012-04-12 JP JP2014513507A patent/JP5980915B2/ja active Active
• 2014
  • 2014-01-16 US US14/157,251 patent/US9178336B2/en active Active
• 2016
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