Electric lamp or space discharge component or device manufacturi – Process – Spark plug or spark gap making
Patent
1989-04-06
1990-10-16
Ramsey, Kenneth J.
Electric lamp or space discharge component or device manufacturi
Process
Spark plug or spark gap making
21912164, H01T 2102
Patent
active
049631128
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a spark plug for internal combustion engines. A spark plug is already known (U.S. Pat. No. 4,540,910) in which an intermediate layer is arranged between the metal electrode, which consists of a nickel alloy, and a highly wear-resistant metal coating consisting of a platinum containing alloy, which intermediate layer serves to compensate for the sharply diverging heat expansion behavior of the metal electrode and the metal coating; this intermediate layer consists of an alloy which is composed of a platinum alloy and nickel. In order to apply the wear-resistant metal coating to the metal electrode, the wear-resistant metal coating is first mechanically plated together with the intermediate layer and the intermediate layer, provided with the metal coating is then connected with the metal electrode by resistance welding.
A spark plug in which a coating of noble or precious metal such as platinum is attached to the free end face of the center electrode by resistance welding has also already been described in the DE-PS No. 31 32 814. In this center electrode, however, there is the problem that the noble metal layer becomes detached from the center electrode because of stresses in the connecting region during higher thermal and corrosive loads.
The DE-PS No. 22 56 823 shows a spark plug with a center electrode whose end face is protected against high wear by a platinum piece. This platinum piece is provided with an intermediate layer plated thereon in a similar manner to the example according to the U.S. Pat. No. 4,540,910 cited above; this intermediate layer comprises a material which possesses the same or approximately the same high resistance to temperature and corrosion and thermal expansion characteristic as the center electrode itself. This intermediate layer consists of a nickel-base alloy of which the center electrode itself can also be composed. This intermediate layer is connected with the center electrode by welding, particularly by resistance welding. When using such spark plugs in internal combustion engines, it has also been found out that the fastening of the platinum pieces on the electrodes is not satisfactory.
SUMMARY OF THE INVENTION
The invention has the object of developing a method of producing a spark plug in which an connection of the metal electrode and wear-resistant metal coating is achieved, and the production of which can be carried out at a low cost.
This object is achieved by arranging a metal piece formed of a noble material on the gap facing end face of an electrode and directing laser beams onto the metal piece to form an alloy zone between the end face of the electrode and a wear-resistant layer, which alloy zone consists of the materials of the electrode and the metal piece with the proportion of the electrode material continuously decreasing from an area adjacent to the end face of the electrode which includes only electrode material, to an area adjacent the wear-resistant layer which includes only the material of the metal piece connecting the metal electrode and wear-resistant metal coating is very simple because it requires only a single metal piece without a second metal piece to be plated thereon to provide the wear-resistant metal coating on the metal electrode. Moreover, the process is suitable for large-series production without difficulties and ensures that the wear-resistant metal coatings arranged on the metal electrodes are maintained with a long working life in all occurring operating conditions in the internal combustion engine.
These and other objects and advantages of the present invention will be best understood from the following description of the preferred embodiment with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an enlarged partial longitudinal cross-sectional view of the area of a spark plug on the combustion chamber side;
FIG. 2 shows a partial enlarged longitudinal cross-sectional view, of the center electrode on the combustion chamber side, according t
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patent: 4581558 (1986-04-01), Takumura et al.
patent: 4670684 (1987-06-01), Kagawa et al.
patent: 4786267 (1988-11-01), Toya et al.
patent: 4853582 (1989-08-01), Sato et al.
Benedikt Walter
Friese Karl-Hermann
Herden Werner
Schuldt Dietrich
Steinke Leo
Ramsey Kenneth J.
Robert & Bosch GmbH
Striker Michael J.
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