Spark plug for internal combustion engines

Details Spark plug for internal combustion engines Spark plug for internal combustion engines

1995-06-05

1996-08-27

O'Shea, Sandra L.

Electric lamp and discharge devices

Spark plugs

Non-conducting material in or adjacent gap

313131R, 313137, H01J 1338

Patent

active

055504248

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a spark plug for an internal combustion engine. In particular, the present invention relates to a spark plug having a coating to protect against misfirings and cold-starting difficulties.
A spark plug has already been disclosed (German Patent No. DE 31 29 025 C2), in which the longitudinal portion (foot) of the insulating body on the combustion-chamber side is provided with a coating which is intended to prevent electrically conductive deposits and is composed of a paraffin solution containing at least 0.1% silicone oil. According to the Patent Specification, the inner side of the spark-plug metal housing which is adjacent to the insulating-body foot may also be coated with such a coating. To produce the coating, the paraffin and the silicone have to be dissolved in a solvent such as trichloroethylene, chlorobenzene, toluene or the like, whose use is undesirable from physiological points of view and for environmental reasons.
The coating on the insulating-body foot is intended to avoid electrically conductive deposits which form during the operation of internal combustion engines at temperatures of the insulating-body foot below 500.degree. C. These deposits are carbon, water and other electrically conductive substances originating from the fuel. As a consequence of these deposits, energy originating from the ignition system may leak away in an undesirable manner in the form of creepage currents even before the actual ignition time of the internal combustion engine and result in cold-starting problems and misfirings in the internal combustion engine. With their consequences described above, the deposits have a particularly troublesome effect in the case of the installation of spark plugs in new motor vehicles, which often travel only with low speeds and/or low load during their running-in phase of a few hundred km and consequently do not raise the temperature of the insulating-body foot of the spark plugs above the so-called free-burn temperature of 500.degree. C.
Silicone oil was also already proposed for such coatings, but it did not prove to be sufficiently effective and resulted, specifically as a consequence of the penetration of carbon and/or water into the silicone oil layer, in undesirable electrical conductivity of the insulating-body foot.


SUMMARY OF THE INVENTION

The spark plug according to the present invention has, on the other hand, the advantage that the substance used as protection against contamination of the insulating body foot is not only sufficiently effective but is at the same time solvent-free, that is to say physiologically safe and environmentally acceptable. Expensive extraction systems are therefore unnecessary for the application of such coatings. To be regarded as a further advantage is the fact that the coating according to the present invention is resistant to handling and does not lose its protection against contamination even during prolonged storage of such spark plugs.
Advantageous further developments and improvements of the spark plug according to the present invention include that it is particularly advantageous if that inner side of the metal housing which is adjacent to the insulating-body foot is also covered with such a coating. As a consequence of this measure, the undesirable leakage of energy is prevented still further and, in addition, the application of the coating is also generally simplified.


BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows an enlarged representation of a spark plug in longitudinal view with a section through its end portion on the combustion-chamber side .


DETAILED DESCRIPTION OF THE INVENTION

The (high-voltage) spark plug 10 shown in the FIGURE of the drawing has an essentially tubular metal housing 11 which has, on its outer side, a screw insertion thread 12 and a hexagonal nut head 13 as means for the installation of the spark plug 10 in an internal combustion engine, which is not shown, in particular in an internal combustion engine of motor vehicles. In the region of i

REFERENCES:
patent: 3345532 (1967-10-01), Mattarella
patent: 4415828 (1983-11-01), Mizuno et al.
patent: 4427914 (1984-01-01), Mizuno et al.
patent: 4798991 (1989-01-01), Benedikl et al.
patent: 5274298 (1993-12-01), Cassidy et al.

Affiliated with

Also associated with

Rating

Spark plug for internal combustion engines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Spark plug for internal combustion engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spark plug for internal combustion engines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1058005