{"id":2338,"date":"2023-02-07T23:05:52","date_gmt":"2023-02-07T14:05:52","guid":{"rendered":"https:\/\/am.denso.com\/plug-global\/?page_id=2338"},"modified":"2023-02-23T11:34:27","modified_gmt":"2023-02-23T02:34:27","slug":"history","status":"publish","type":"page","link":"https:\/\/am.denso.com\/plug-global\/products\/history\/","title":{"rendered":"HISTORY OF DENSO SPARK PLUG"},"content":{"rendered":"\n
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<\/p>\n

HISTORY OF
DENSO SPARK PLUG<\/p>\n<\/div>\n\n\n\n

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\u25cf<\/p>\n <\/div>\n<\/div>\n\n\n\n

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    \n

  • 1959<\/p>

    P2 plug<\/b><\/p><\/li>\n

  • 1962<\/p>

    P3 plug<\/p><\/li>\n

  • 1970<\/p>

    Wide plug<\/p><\/li>\n

  • 1972<\/p>

    G plug<\/p><\/li>\n

  • 1973<\/p>

    Resistor plug<\/p><\/li>\n <\/ul>\n<\/div>\n\n

    \n

    HISTORY<\/span>
    1959 – 1974<\/h2>\n

    Technology Development – Issues<\/h3>\n

    \n 1955, concluded technical assistance agreement with Robert Bosch.
    \n 1957, instituted the spark plug lab and started the introduction of plug technology from Bosch.
    \n Dispatched engineers to each other starting in 1958 with the aim of quickly learning the manufacturing technology.
    \n Implemented improvement activities and creative efforts and launched the sales of the P2 plug with excellent mass producibility a year later in 1959. The speed of development was fairly high considering that we started from a base of zero.
    \n In 1960, we were awarded an order for plugs from Toyota Motor Corporation (at that time).
    \n The P2 plug was adopted for the Type R engine installed in the Crown and other cars.\n <\/p>\n

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    \n
    \n
    \n \n
    \n \n
    \n \"P2\n

    P2 plug<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cP2\u201d\n

    \u201cP2\u201d Plug announcement reception<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cP2\u201d\n

    \u201cP2\u201d Plug announcement reception<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"P3\n

    P3 plug<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cP3\n

    \u201cP3 plug\u201d pamphlet<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cDENSO\n

    \u201cDENSO Technical Report\u201d Sep 1962 Volume<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"Wide\n

    Wide plug<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cPocket\n

    \u201cPocket Chart\u201d (1972)<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"G\n

    G plug<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"\u201cDENSO\n

    \u201cDENSO Plug G\u201d pocket manual (1972)<\/p>\n <\/figure>\n <\/div>\n \n

    \n
    \n \"Resistor\n

    Resistor plug<\/p>\n <\/figure>\n <\/div>\n \n <\/div>\n \n <\/div>\n <\/div>\n <\/div>\n <\/div>\n <\/div>\n<\/div>\n<\/div>\n\n\n\n

    \n\n
    \n
      \n

    • 1975<\/p>

      GU plug<\/p>

      3-electrode plug<\/p>

      Wide U Plug<\/b><\/p><\/li>\n

    • 1976<\/p>

      Double-electrode plug<\/p><\/li>\n

    • 1977<\/p>

      Semi-surface plug<\/p><\/li>\n

    • 1979<\/p>

      4-electrode plug<\/p><\/li>\n <\/ul>\n<\/div>\n\n

      \n

      HISTORY<\/span>
      1975 – 1979<\/h2>\n

      Company Background<\/h3>\n

      \n A dramatic improvement in the performance and quality of spark plugs was required under emissions regulations starting in the 1970s.
      \n To turn emissions green, a plug with a good ignitability to burn a lean mixture without having to dilute the fuel-air mixture is required.\n <\/p>\n

      Technology Development – Issues<\/h3>\n

      \n To raise the ignitability of the plug, a variety of approaches from the perspective of the engine, ignition power source etc. is available.
      \n It is necessary to prevent the energy of the flame kernel generated by electrical discharge from being absorbed by the center electrode and grounding electrode so as to reduce the flame extinguishing effect to allow the flame kernel to grow. To resolve the problem, methods such as using a wide gap and making the center electrode thinner etc. were already known.
      \n However, it is also known that these methods have opposing disadvantages e.g. the sparking voltage rises, or the plug life is shortened and so on. Consequently, it was extremely difficult to find a solution, but the development team conducted a thorough study of the flame extinguishing effect and electrode shape to derive a conclusion.\n <\/p>\n

      Technology Development – Solutions<\/h3>\n

      \n By making a U-shaped groove on the grounding electrode side, the same effect as a wide gap was realized. By studying the ignitability, heat resistance, producibility etc. and giving form to the conclusion, the world\u2019s first U-groove plug was born.
      \n Subsequently, improvements in the technology can also be seen in the plugs launched by other companies which have a cross-shaped or V-shaped groove on the center electrode side to achieve the same effect. Employing a U-shaped groove, the DENSO plug Wide U was awarded patents in 5 countries including the US, UK, France, Germany and Italy, becoming a globally patented plug both in name and reality.\n <\/p>\n\n\n\n

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      \n \n
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      \n \"GU\n

      GU plug<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"3-electrode\n

      3-electrode plug<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"Wide\n

      Wide U Plug<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"\u201cWide\n

      \u201cWide U Plug\u201d record jacket<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"\u201cWide\n

      \u201cWide U Plug\u201d TV CM<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"Double-electrode\n

      Double-electrode plug<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"Semi-surface\n

      Semi-surface plug<\/p>\n <\/figure>\n <\/div>\n \n

      \n
      \n \"4-electrode\n

      4-electrode plug<\/p>\n <\/figure>\n <\/div>\n \n <\/div>\n \n <\/div>\n <\/div>\n <\/div>\n <\/div>\n<\/div>\n \n \n<\/div>\n<\/div>\n\n\n\n

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      • 1981<\/p>

        Extended plug<\/p><\/li>\n

      • 1982<\/p>

        Small hex plug<\/p>

        Platinum plug<\/b><\/p><\/li>\n

      • 1983<\/p>

        ZU plug<\/b><\/p><\/li>\n

      • 1995<\/p>

        Double-electrode
        Platinum plug<\/p><\/li>\n <\/ul>\n <\/div>\n \n

        \n

        HISTORY<\/span>
        1980 – 1995<\/h2>\n

        Company Background<\/h3>\n

        \n At the beginning of the 1980s, combustion with an even leaner fuel-air mixture was required from the perspective of improving fuel efficiency and complying with stringent emissions regulations. Plugs were also required to tackle highly difficult challenges such as unprecedented improvements in the ignition performance and reducing the rise in the sparking voltage. Moreover, following improvements in engine performance, engine design became more complex, and plugs were also required to have a longer lifespan and be maintenance-free as it became difficult to install and remove the plugs.\n <\/p>\n \n

        Technology Development<\/h3>\n

        \n To deal with such issues, the development staff focused their attention on platinum, a precious metal which has an excellent corrosion resistance and spark resistance, to make the center electrode thinner, and created a method to weld a thin platinum tip on only the electrode discharge section so as to keep the cost low.
        \n However, it did not mean that the technical problems were resolved with this. Due to the difference in the coefficient of expansion between platinum and the electrode base material, a problem occurred due to the platinum tip peeling off. Therefore, we finally succeeded in commercializing the product by controlling the changes in the platinum thickness after welding and the thickness of the alloy layer at the bonding boundary in micron units, in addition to strictly controlling the material of the platinum tip and the power conditions of the resistance welding. We were then able to file a patent for it too. In this way, a platinum plug employing a platinum tip only in the electrical discharge section was launched in Aug 1982.\n <\/p>\n \n

        Development After Launch<\/h3>\n

        \n This platinum plug has a durability of 100,000 km and was mainly installed in Toyota cars for the US market initially. Subsequently, it was employed in other cars one after another such as taxis which have a high mileage, one-box cars for which it is difficult to replace the plugs due to the engine mounting position, luxury cars which need to be maintenance-free and so on.\n <\/p>\n \n

        Technology Development<\/h3>\n

        \n In 1983, the ZU plug was developed for users who prefer high performance plugs. Initially, this newly developed ZU plug was used experimentally by race users etc. for road races, motocross and dirt races in the US, but it was then launched officially as a high grade type of general plug.
        \n This ZU plug employed platinum in the center electrode to realize a center electrode with the world\u2019s smallest diameter (0.7 mm) at that time. Furthermore, we succeeded in improving the sparking performance and ignition performance by employing a taper cut at the tip of the grounding electrode. By using a center electrode with a fine diameter of 0.7 mm, it is possible to create sparks at a low voltage, allowing a good starting characteristic and efficient combustion to be obtained.\n <\/p>\n \n

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        \n \n
        \n \n
        \n
        \n \"Extended\n

        Extended plug<\/p>\n <\/figure>\n <\/div>\n \n

        \n
        \n \"Small\n

        Small hex plug<\/p>\n <\/figure>\n <\/div>\n \n

        \n
        \n \"Platinum\n

        Platinum plug<\/p>\n <\/figure>\n <\/div>\n \n

        \n
        \n \"ZU\n

        ZU plug<\/p>\n <\/figure>\n <\/div>\n \n

        \n
        \n \"\u201cZU\n

        \u201cZU Plug\u201d leaflet<\/p>\n <\/figure>\n <\/div>\n \n

        \n
        \n \"Double-electrode\n

        Double-electrode Platinum plug<\/p>\n <\/figure>\n <\/div>\n \n <\/div>\n \n <\/div>\n <\/div>\n <\/div>\n <\/div>\n <\/div>\n <\/div>\n<\/div>\n\n\n\n

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        • 1997<\/p>

          Iridium plug<\/b><\/p><\/li>\n

        • 1998<\/p>

          IRIDIUM POWER<\/p><\/li>\n

        • 2003<\/p>

          Double needle
          Iridium plug<\/b><\/p><\/li>\n

        • 2008<\/p>

          TT plug<\/b><\/p><\/li>\n

        • 2018<\/p>

          Total production of
          6 billion plugs<\/span>
          achieved<\/b><\/p><\/li>\n <\/ul>\n <\/div>\n \n

          \n

          HISTORY<\/span>
          1996 – 2018<\/h2>\n \n

          Technology Development<\/h3>\n

          \n In 1997, the company developed a new plug using a precious metal as a base to replace the platinum plug. This is the iridium plug with an ultra-thin electrode which made it possible to extend its life by using an iridium alloy in the center electrode.
          \n The iridium plug dramatically improves the wear resistance compared to previous platinum plugs, allowing the electrode to be made even thinner and further improving the ignitability and electrical discharge property compared to before.
          \n Besides achieving an astonishing durability of 200,000 km with its focus on the lifespan, the iridium plug also succeeded in stabilizing the combustion.
          \n In 1998, based on the technology developed, we created a new generation of high-performance plugs employing an iridium alloy with a diameter of 0.4 mm.
          \n Named as [IRIDIUM POWER], this plug succeeded in lowering the sparking voltage and improving the ignition performance by employing a grounding electrode which combines our proprietary U-groove and taper cut, and an ultra-thin center electrode with the world\u2019s smallest diameter of 0.4 mm, allowing a reliable combustion to be obtained in all operating ranges.\n <\/p>\n \n

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          \n \"Iridium\n

          Iridium plug<\/p>\n <\/figure>\n <\/div>\n \n

          \n
          \n \"IRIDIUM\n

          IRIDIUM POWER<\/p>\n <\/figure>\n <\/div>\n \n

          \n
          \n \"\u201cIRIDIUM\n

          \u201cIRIDIUM POWER\u201d pamphlet<\/p>\n <\/figure>\n <\/div>\n \n

          \n
          \n \"\u201cIRIDIUM\n

          \u201cIRIDIUM POWER\u201d POP<\/p>\n <\/figure>\n <\/div>\n \n

          \n
          \n \"Double\n

          Double needle Iridium plug<\/p>\n <\/figure>\n <\/div>\n \n

          \n
          \n \"TT\n

          TT plug<\/p>\n <\/figure>\n <\/div>\n \n <\/div>\n \n <\/div>\n <\/div>\n <\/div>\n <\/div>\n <\/div>\n \n <\/div>\n \n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n\n\n