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
  • H01T13/39—Selection of materials for electrodes

Definitions

• This invention relates generally to spark ignition devices, such as spark plugs for internal combustion engines, and more particularly to the alloys used to make the sparking surface of the sparking electrode of such devices.
• Various precious metal alloys are used for the sparking surfaces of spark plug electrodes. Some of the precious metal elements are less costly than others, but there is sometimes a trade-off in terms of the properties that can be achieved using the less costly alloy alternatives.
• palladium is a relatively low cost element, however it has been found to oxidize in the operating environment of spark plug sparking surfaces.
• the palladium used in sparking surfaces made from alloys of rhenium- palladium or platinum-palladium-iridium alloys has been shown to oxidizes during use.
• alloying gold with palladium has the beneficial effect of mitigating the oxidation of palladium under the operating environment of a spark plug electrode.
• known palladium-gold alloys e.g., Au40Pd
• the known palladium-gold alloy materials are prone to alloy with the combustion constituents present in the operating environment, such as lead, thereby causing the material to degrade in use.
• a spark ignition device such as a spark plug
• an electrode sparking tip made from a AuPd alloy with the addition of a precious metal element of at least 3 wt.% selected from at least one of platinum, indium, rhodium and ruthenium.
• the gold counteracts oxidation of the palladium and the additional element or elements provide high temperature mechanical properties and resistance to alloying with the combustion constituents during use.
• the Au makes up at least 10 wt.% of the sparking tip.
• the AuPd alloy makes up at least 40 wt.% of the sparking tip, with the additional precious metal element making up the difference.
• Rh and/or Ru alloy can be diluted with a non-precious metal, such as Ni (up to about 30 wt.%), and further include the addition of small amounts of W (1-4 wt.%) for lowering work function, and optionally small amounts of one or more reactive elements, such as Zr, Y, La, Hf, Ta at 0.01 - 0.2 wt% for grain stabilization.
• a non-precious metal such as Ni (up to about 30 wt.%)
• W 1-4 wt.%) for lowering work function
• one or more reactive elements such as Zr, Y, La, Hf, Ta at 0.01 - 0.2 wt% for grain stabilization.
• Figure 1 is a cross-sectional elevation view of an ignition device with an electrode sparking tip constructed in accordance with the invention.
• Figure 2 is an enlarged view of the encircled region 2 of Figure 1.
• Figure 1 illustrates a spark ignition device 10 constructed in accordance with one presently preferred aspect of the invention for use in igniting a fuel/air mixture in internal combustion engines.
• the exemplary spark ignition device 10 is illustrated in the form of a spark plug, but the invention contemplates other ignition devices to be within the scope of the claims, such as glow plugs, for example.
• the device 10 includes an annular ceramic insulator 12 fabricated of aluminum oxide or another suitable electrically insulating material in known manner.
• the insulator 12 has a central passage 14 extending longitudinally between an upper terminal end 16 and a lower nose or core end 18 in which a center electrode 20 is disposed.
• the center electrode 20 has a sparking surface, referred to hereafter as sparking tip 21, at a free end thereof.
• An electrically conductive metal shell 22 is disposed in sealed relation about the lower and mid portions of the insulator 12 and may be made from any suitable metal, such as various steel alloys, and may be coated with a Zn or Ni-base alloy coating or the like in known manner.
• the shell 22 includes at least one ground electrode 24 which may have any of a number of shapes, sizes and configurations, such as the standard single L-shaped configuration illustrated in the drawings, for example.
• the ground electrode 24 has at least one ground electrode sparking surface, referred to hereafter as sparking tip 25, that is spaced across a spark gap 26 from the sparking tip 21 of the center electrode 20.
• At least one of the sparking tips 21, 25 is constructed from AuPd alloy with the addition of at least one of platinum, iridium, rhodium and ruthenium of at least 3 wt.%.
• the gold counteracts oxidation of the palladium and the additional element adds the needed high temperature mechanical properties and resistance to alloying with the combustion constituents during use.
• An electrically conductive terminal stud 28 is disposed in the central passage 14 of the insulator 12 with a free lower end 32 of the terminal stud 28 being disposed adjacent a resistor layer 30 which is arranged between the lower end 32 and an upper end 34 of the center electrode 20.
• Conductive glass seals 36, 38 separate the resistor layer 30 from the stud 28 and center electrode 20, respectively.
• This resistor layer 30 can be made from any suitable composition used in such applications to suppress electromagnetic interference (EMI).
• EMI electromagnetic interference
• the terminal stud 28, upper glass seal 36, resistor layer 30, lower glass seal 38 and center electrode 20 provide an electrical path, whereas the shell 22 and ground electrode 24 provide a ground path spaced from the electrical path across the spark gap 26.
• At least one or both of the sparking tips 21, 25 are constructed of a AuPd- based alloy, whereas the center electrode 20 and ground electrode 24 can be fabricated of a material other than that used to construct the sparking tips 21, 25. If both sparking tips 21 , 25 are constructed of a AuPd-based alloy, they may be of the same or different AuPd- based alloy composition. As illustrated, the sparking tips 21, 25 are conductively joined, such as by welding, to the center and ground electrodes 20, 24, respectively.
• the mechanism of attachment of the sparking tips 21, 25 may be performed utilizing any suitable mechanism of attachment, and further, that the shape of the sparking tips 21, 25 may by other than as described or shown, such as disc, cylinders, rivets, bars, or other shapes, as desired.
• the AuPd-based alloy is prealloyed with at least one precious metal effective to increase the high temperature performance properties and increase the mechanical strength of the finished sparking tip material to levels suitable for modern sparking surface applications, as well as to prevent the AuPd constituents from further alloying and breaking down in the presence of common combustion constituents, such as lead.
• One such precious metal found to be effective in increasing the mechanical strength of the finished sparking tip material and in preventing or inhibiting unwanted alloying is platinum (Pt).
• Alloys of 55 wt.% Au, 40 wt.% Pd and 5 wt.% Pt; 50 wt.% Au, 30 wt.% Pd and 20 wt.% Pt; and 50 wt.% Au, 40 wt.% Pd and 10 wt.% Pt have proven to be effective as low cost sparking tip materials for spark plugs, while providing the desired mechanical strength and resistance to alloying in use.
• the Pt can be added in ranges of 3-50 wt.%, 5-20 wt.% or 5-10 wt.% to an alloy of AuPd which is alloyed in a ratio of about 1.5: 1, while AuPd alloyed ratios of 0.25:1 to 2:1 are also contemplated herein.
• one or more additional precious metals may be added to the AuPd alloy, such as Ir, Rh and/or Ru either in combination with Pt or in place of Pt.
• an alloy of 46 wt.% Pt, 34 wt.% Pd, 10 wt.% Au and 10 wt.% Ir has shown to be an effective alloy for sparking tips of spark plugs.
• these alloys can be diluted with non-precious metals, such as Ni and can include small amounts of W (1 to 4 wt.%) for lowering work function.
• these alloys can be further alloyed with small amounts of one or more reactive elements, such as Zr, Y, La, Hf or Ta in amounts from 0.01 - 0.2 wt.% as a grain stabilizer for the alloy.
• the sparking tips 21, 25 can be fabricated of AuPd-based alloys having an Au content greater than 10 wt.% and a Pd content greater than 5 wt.% in combination with at least one of Pt, L", Rh or Ru.
• This material may be further alloyed with small amounts of W as discussed above, as well as optionally being alloyed with one or more reactive elements as discussed above.

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• Spark Plugs (AREA)
• Ignition Installations For Internal Combustion Engines (AREA)

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• 2009
  • 2009-05-18 US US12/467,528 patent/US7969078B2/en not_active Expired - Fee Related
  • 2009-05-19 CN CN200980128372XA patent/CN102099977B/zh not_active Expired - Fee Related
  • 2009-05-19 KR KR1020107027393A patent/KR20110021852A/ko not_active Withdrawn
  • 2009-05-19 EP EP09751323A patent/EP2294664A4/en not_active Withdrawn
  • 2009-05-19 JP JP2011510632A patent/JP2011521428A/ja not_active Withdrawn
  • 2009-05-19 WO PCT/US2009/044432 patent/WO2009143095A2/en not_active Ceased

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