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
• • 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

Definitions

• the invention relates to a spark plug for internal combustion engines according to the preamble of the main claim.
• a spark plug is already known (US Pat. No. 4,540,910), in which an intermediate layer is arranged between the metal electrode consisting of a nickel alloy and a metal layer of high wear resistance made of a platinum-containing alloy, which layer compensates for the very different Thermal expansion behavior of metal electrode and metal pad is used; this intermediate layer consists of an alloy which is composed of a platinum alloy and nickel.
• the wear-resistant metal coating is first mechanically plated with the intermediate layer and then the intermediate layer provided with the metal coating is connected to the metal electrode by resistance welding.
• a spark plug has also already been described in DE-PS 31 32 814, in which on the free end face of the center electrode a plate made of precious metal such as platinum is attached by resistance welding. In this, however, the center electrode. Problem occurs that the precious metal flakes, due to st l ⁇ of voltages in. The connecting zone at higher thermal loads and korro ⁇ immersive from the center electrode '.
• DE-PS 22 56 823 shows a spark plug with a central electrode, the end face of which is protected against high wear by a piece of platinum. Similar to the example according to US Pat. No. 4,540,910 mentioned earlier, this piece of platinum is provided with a latified intermediate layer; this intermediate layer consists of a material which has the same or approximately the same high temperature resistance, corrosion resistance and thermal expansion characteristic as the center electrode itself; According to a subclaim, this intermediate layer consists of a nickel-base alloy, from which the center electrode itself can also consist. This intermediate layer is connected to the center electrode by welding, in particular by resistance welding. When using such spark plugs in internal combustion engines, it has also been shown that the fastening of the platinum pieces on the electrodes was unsatisfactory.
• the invention is based on the object of developing a method for producing a spark plug, whereby an improvement in the connection of the metal electrode and wear-resistant metal coating is achieved and that it can be carried out more cost-effectively.
• This object is achieved according to the invention by the method for producing spark plugs with the characterizing features of the main claim.
• This method of connecting the metal electrode and wear-resistant metal pad is so simple because it is requires only a single piece of metal and not yet a second piece of metal to be coated for the wear-resistant metal support on the metal electrode.
• the method is suitable for large series production without any problems and ensures that the wear-resistant metal pads applied to the metal electrodes are kept in the internal combustion engine with a long service life under all operating conditions.
• FIG. 1 shows a longitudinal section through the area of a spark plug on the combustion chamber side in an enlarged view
• FIG. 2 shows the area of the center electrode according to FIG. 1, shown partly in a longitudinal section, in a further enlarged view (preliminary stage: metal piece not yet connected to the center electrode)
• FIG 3 shows a representation similar to the representation according to FIG. 2 (metal piece connected to the central electrode via an alloy zone).
• the ignition-side end region of the metal housing is designated by 11 and the longitudinal bore of this metal housing 11 bears the reference number 12. Inside this longitudinal bore 12 of the metal housing 11, the insulating body 13 is arranged, the combustion body of which end face 14 on the room side with the combustion chamber end face 15 of the metal housing 11 is essentially flush.
• the insulating body 13 is provided on its circumferential surface with an annular pump chamber 16 which essentially adjoins the end face 14 of the insulating body 13 and is connected via an annular gap 17 to the combustion chamber of the internal combustion engine, which is not particularly shown.
• the pump chamber 16 ensures that no conductive bridge of deposits is formed in the plane of the end face 14 of the insulating body 13 between the insulating body 13 and the metal housing 11; this annular gap 17 is kept free by the fact that the fuel vapor air in the pump chamber 16 Mixture (not shown) expands at the time of ignition, blows through the annular gap 17 and thus removes any deposits.
• the insulating body 13 has a longitudinal bore 18, in which a first metal electrode 19 is guided and which projects over the end face 14 of the insulating body 13 at the burning roughness
• this metal electrode 19 can also end flush with the end face 14 of the insulating body 13, but may also protrude further from the longitudinal bore 18 of the insulating body 13.
• This first metal electrode 19 usually runs in the longitudinal axis of the spark plug 10 and is usually referred to as Designated center electrode
• the free end portion of the first metal electrode 19 facing the space is provided with a metal support 20 made of a material with high wear resistance (precious metal), which preferably consists of platinum or a platinum alloy.
• This second metal Electrode 22 is usually fastened to the combustion chamber end section of metal housing 11 (for example by welding) and is electrically connected to ground and consequently then represents the so-called ground electrode.
• the second metal electrode 22 is hook-shaped and has in the area of its metal support 20A has a smaller cross section than in the area where it is connected to the metal housing 11.
• the heat absorbed by the second metal electrode 22 when the spark plug 10 is in operation is quickly released to the metal housing 11, specifically to the area which also carries the screw-in thread 11A and which quickly applies the heat delivers the engine block.
• the invention relating to the metal pads 20, 20A is not limited to a spark plug 10 described above, which has both an air spark gap 21 and a combined sliding spark-air spark gap (14, 17, 11 ), but is suitable for all spark plugs that have at least one metal electrode.
• the so-called center electrode shows the method by which the metal coating 20 made of a noble metal is applied to the end face 23 on the combustion chamber side;
• platinum is used as the material with high wear resistance.
• the center electrode 19 in the present example and also usually consists of a nickel alloy and has a diameter d in the range from 0.8 to 2.5 mm, but preferably between 1 and 1.3 mm.
• the end face 23 directed towards the spark gap 21 is covered with a metal piece 24 which is made of the material with high wear resistance, that is to say from platinum or a platinum alloy exists and has a thickness s of 0.3 mm; the thickness s of this metal piece 24 is between 0.2 and 0.5 mm, but preferably between 0.25 and 0.35 mm.
• the metal piece 24 has a diameter that essentially corresponds to the diameter d of the center electrode 19; depending on the application, the diameter of this metal piece 24 can, however, also be slightly smaller or somewhat larger than the diameter d of the center electrode 19.
• the top side of the metal piece 24 facing the air spark gap 21 is designated by 25.
• a drop-ball-like or cap-like metal piece can also be arranged on the end face 23, if appropriate also on a roughened, grooved or provided with one or more depressions (not shown) end face 23; a flat dome-shaped depression is particularly suitable for reducing shear stresses.
• Laser beams L are then directed onto the upper side 25 of the metal piece 24 in such a way that they run essentially parallel to the imaginary center line M of the first metal electrode 19 and are dimensioned such that in the area of the underside 26 of the metal piece 24 and the end face 23 of the center electrode 19 forms an alloy zone 27.
• this alloy zone 27 does not penetrate into the wear-resistant layer 28 made of platinum or a platinum alloy facing the spark gap 21.
• this alloy zone 27 is constructed in such a way that the layer-shaped region 29 facing the metal electrode 19 consists solely of the material of the center electrode 19, that is to say of a nickel alloy, that the proportion of the material of this center electrode 19 within the alloy zone 27 in richness tion on their layer-shaped region 30 facing the wear-resistant layer 28 tends to continuously decrease, so that in the the wear-resistant layer 28 facing layer-like region 30 no longer contains any material of the center electrode 19.
• the thickness of such an alloy zone 27 is between 50 and 200 ⁇ m, preferably between 100 and 150 ⁇ m.
• the alloy zone 27 extends into a depression 31 which extends in the shape of a cone or dome into the center electrode 19; the lowest point of this depression 31 lies in the region of the center line M of the center electrode 19.
• a particularly secure connection between the metal support 20 and the metal electrode 19 can be achieved if the central electrode 19 makes a rotary movement R around its center line M during the connection process; If the metal electrode 19 is rotated about its center line M when the method is used, it is also possible to direct the laser beams L obliquely onto the upper side 25 of the metal piece 24 and thus to obtain a more favorable alloy zone 27.
• Pulsed laser beams are preferably used in this method; However, oscillating laser beams can also be used. - Due to this structure of an alloy zone 27, the different expansion behavior of the material of the metal electrode 19 and the metal support 20 is compensated and consequently the metal support 20 is prevented from falling off the metal electrode 19.
• the metal piece 24 used has a larger diameter than the metal electrode 19; if necessary, the jacket region adjoining the end face 23 of the metal electrode 19 can be frustoconical or designed as a shoulder, as a result of which then the metal coating extends over a predetermined area of the jacket of the metal electrode 19.
• the above statements directed to the metal support 20 apply correspondingly to the metal support 20A on the second metal electrode 22 and also to differently designed metal electrodes or multiple electrodes.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Spark Plugs (AREA)

Applications Claiming Priority (2)

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• 1987
  • 1987-08-18 DE DE19873727526 patent/DE3727526A1/de not_active Withdrawn
• 1988
  • 1988-07-14 JP JP63505834A patent/JPH02500704A/ja active Pending
  • 1988-07-14 WO PCT/DE1988/000435 patent/WO1989001717A1/de not_active Application Discontinuation
  • 1988-07-14 EP EP19880905703 patent/EP0329721A1/de not_active Ceased
  • 1988-07-14 US US07/340,003 patent/US4963112A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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