Electric lamp and discharge devices – Spark plugs – Plural part insulating means
Patent
1987-01-20
1988-05-24
DeMeo, Palmer C.
Electric lamp and discharge devices
Spark plugs
Plural part insulating means
315 59, H01N 1338
Patent
active
047468343
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an ignition plug. Such an ignition plug, which is known for example from DE-OS No. 23 63 804, has a capacitor which is built into the ignition plug and arranged so as to be electrically parallel with respect to the spark gap. This capacitor should store enough energy in the vicinity of the spark gap of the ignition plug so that the ionizing initial phase of the spark during the sparking passage at the spark gap of the ignition plug brings about a sure ignition of the fuel vapor/air mixture found in the internal combustion engine. The aforementioned DE-OS No. 23 63 804 also describes such an ignition plug which, in addition, has a preliminary spark gap which is likewise built into the ignition plug and is electrically connected in series with the spark gap. However, the aforementioned DE-OS discloses no indications of an embodiment form of such an ignition plug which can be realized in an economical manner and whose functioning is ensured.
Another ignition plug with a built-in capacitor is known from DE-OS No. 34 04 081; the insulating body of this ignition plug, which comprises a plurality of longitudinal portions, has an average dielectric constant such that this ignition plug has a capacity of 20 to 100 pF, preferably 30 to 80 pF. However, the capacitor of this ignition plug has the object of reducing or suppressing the electromagnetic interference of the internal combustion engine so as to prevent disturbances in radio and television equipment and the like.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an, the ignition plug, according which can be realized in an economical manner and is able to ignite even meager fuel vapor/air mixtures under all operating conditions of an internal combustion engine reliably and for the duration of the required service life.
It is particularly advantageous if annular elements for electrical insulation are arranged between the separating surfaces extending transversely through the ceramic insulating body of the ignition plug, which annular electrical insulation elements securely contact the separating surfaces and consist of a material which is elastic at all temperatures occurring in this area; for example, these elements can consist of silicon rubber or correspondingly adjusted epoxy resin. Moreover, it is advisable that the affected separating surfaces of the insulating body have a roughness depth R.sub.Z of less than 30 .mu.m; this can be achieved, for example, by means of a glaze. In accordance with the German industrial standard, roughness depth R.sub.Z designates the average value of the individual roughness values Z.sub.1. . . Z.sub.5 of five consecutive individual measured lengths. Due to this type of assembly of the insulating body, no expensive sintering equipment is required for the connection of the longitudinal portions of the insulating body and a reliable storage of electrical energy in the ignition plug is nevertheless ensured.
In order to reduce the electrode wear, and a possible spark glide path erosion, and thus improve the operating reliability and service life in such ignition plugs it is advantageous to leave gas gaps of 0.01 to 0.50 mm, but preferably 0.05 to 0.30 mm, between the dielectric structural cmponent part and the structural component parts which are in a working connection with the latter (connection pins, metal housing); air is preferably used as gas.
BRIEF DESCRIPTION OF THE DRAWING
The single FIGURE of the drawing shows a longitudinal section through an ignition plug, according to the invention, on enlarged scale.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The ignition plug 10 shown in the drawing has a substantially tubular metal housing 11 which, as means for the installation of this ignition plug 10 in a motor cylinder head (not shown), comprises on its outside a screw-in thread 12, a wrench hexagon 13 and a sealing ring 14. In the area of its end on the combustion chamber side, this metal housing 11 has a hook-shaped ground electrode 15, w
REFERENCES:
patent: 3295005 (1966-12-01), Poellet et al.
patent: 4549114 (1985-10-01), Herden
patent: 4568855 (1986-02-01), Nemeth et al.
Barthelma Ludwig
Bauerle Adalbert
Benedikt Walter
Herden Werner
Holl Walter
DeMeo Palmer C.
Robert & Bosch GmbH
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