Spark plug having Y-shaped or V-shaped electrodes

Details Spark plug having Y-shaped or V-shaped electrodes Spark plug having Y-shaped or V-shaped electrodes

1992-12-24

1994-11-29

Yusko, Donald J.

Electric lamp and discharge devices

Spark plugs

Particular electrode structure or spacing

313140, H01T 1320

Patent

active

053693280

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a spark plug having a center electrode which is insulated relative to the plug screwthread, and ground electrodes which are electrically connected to the plug screwthread, wherein mounted at the combustion chamber end of the center electrode is an attachment portion which at least partially comprises preferably platinum or a platinum alloy, the spark paths lying between the attachment portion and the ground electrodes which go thereto from the side


BACKGROUND OF THE INVENTION

Spark plugs are of interest, which have a very long service life and which in particular exhibit a low level of consumption of the electrodes due to their burning away, but which nonetheless can be operated with relatively low ignition voltages. If necessary they should afford convenient adjustability, with a defined electrode gap.


SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, it is provided that the attachment portion is substantially in the form of a prism which faces with the top surface towards the combustion chamber and the ground electrodes extend laterally beside the side surface of the substantially prism-shaped attachment portion substantially parallel the prism edges of the top surface and the bottom surface, respectively, and that the ground electrodes comprise at least one carrier of base metal or semi-precious metal, preferably nickel, on which is arranged, towards the attachment portion of the center electrode, a thin electrode layer of platinum or a platinum alloy.
It would be desirable in relation to spark plugs to achieve high local field strengths between the center electrode and the ground electrodes in order to require an ignition voltage which is as low as possible. High field strengths of that kind can be achieved by virtue of pointed electrode configurations. However that then involves the disadvantage that such electrodes burn away relatively quickly. A possible form of improvement in that respect lies in the use of suitable materials. However, that has also not given satisfactory results, with the previous electrode geometries. With the electrode geometry corresponding to the present invention, in which the attachment portion on the center electrode of preferably platinum or a platinum alloy essentially involves the outside shape of a prism, the sharp prism edges provide a high local field strength and thus a reduction in the ignition voltage. At the same time the level of electrode consumption due to burning away is kept within limits due to the relatively long effective overall length of the prism edges. With that configuration, the spark paths lie between the attachment portion and the ground electrodes which extend laterally beside the attachment portion substantially parallel to the prism edges of the top surface and the bottom surface, respectively, and they, therefore, practically surround the entire prism-shaped attachment portion. Due to the ground electrodes extending parallel to the side surfaces of the prism-shaped attachment portion of platinum, the electrode consumption which occurs in any case only to a low degree is also relatively uniform, so that, if necessary, that arrangement affords simple adjustability with a well-defined electrode gap.
In the case of the attachment portion on the center electrode, the important consideration in regard to the properties of the plug in terms of electrode burning and ignition sparking is essentially the external shape, in particular the long prism edges, while the bottom surface generally at least contributes to joining the attachment portion to the center electrode. In order to keep down the amount of electrode burning, it is important that the regions of the prism-shaped attachment portion, which are disposed at the spark path, comprise platinum or a platinum alloy, while the center portion can comprise base metal and/or semi-precious metal. Such a version simultaneously permits a firm connection between the attachment portion and the center electrode, while also providing fo

REFERENCES:
patent: 4488081 (1984-12-01), Kondo et al.
patent: 4826462 (1989-05-01), Lenk
patent: 4893051 (1990-01-01), Kondo
patent: 5107168 (1992-04-01), Friedrich et al.
patent: 5189333 (1993-02-01), Kagawa et al.

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