Patent Application
20180026427
This application claims priority to DE 10 2016 113 570.4, filed Jul. 22, 2016, the entire disclosure of which is hereby incorporated herein by reference in its entirety.
The invention relates to a protective sleeve for a corona igniter in a spark plug shaft of an internal combustion engine.
Corona igniters are known, for example, from U.S. Publication No. 2014/116370 A1. Corona igniters cause an ignition in the combustion chamber of an engine by means of a corona discharge and therefore represent an alternative to conventional spark plugs, which cause an ignition by means of an arc discharge.
In comparison with spark plugs, corona igniters make it possible to realize a more precise control of the ignition point, as well as a lower fuel consumption and reduced emissions, but corona igniters are mechanically less robust than spark plugs. For example, corona igniters typically have sensitive ignition tips that can be damaged during the installation into the spark plug shaft of an engine. In addition, vibrations occurring during the operation of the engine can lead to mechanical stresses and to premature failure of a corona igniter.
This disclosure shows how the service life of a corona igniter can be extended and a premature failure thereof be prevented.
The protective sleeve is configured to be inserted into the spark plug shaft of an internal combustion engine. The protective sleeve comprises a collar that is seated on the edge of the spark plug shaft opening and therefore has a greater width than the maximum diameter of the spark plug shaft. The protective sleeve also comprises a tubular section adjacent to the collar and designed for surrounding a corona igniter inside the spark plug shaft. The protective sleeve guides the corona igniter during its insertion into the spark plug shaft and thereby reduces the risk of damaging sensitive ignition tips during the installation of a corona igniter. In addition, the protective sleeve can dampen vibrations of the corona igniter that are generated by the engine.
When the corona igniter is inserted into the spark plug shaft and screwed to the cylinder head, the collar of the protective sleeve is pressed against the rim of the spark plug shaft opening by the corona igniter. The protective sleeve is therefore clamped between the engine block and the corona igniter and can dampen engine-related vibrations of the corona igniter.
According to an advantageous refinement of this disclosure, the tubular section comprises multiple cylindrical sections with different diameters, for example two cylindrical sections with different diameters. A transition section is respectively arranged between two such cylindrical sections and connects the two cylindrical sections to one another. For example, the transition section may have a conical shape.
According to another advantageous refinement of this disclosure, the underside of the collar carries a seal or gasket that rests on the rim of the spark plug shaft opening after the insertion of the protective sleeve into the spark plug shaft. The seal may be realized, for example, in the form of an O-ring or a sealing lip and can additionally improve the vibration-damping effect of the protective sleeve. The seal or gasket may be seated, for example, in an annular groove on the underside of the collar.
According to another advantageous refinement of this disclosure, it is proposed that the collar carries a seal or gasket for sealing an annular gap between the protective sleeve and the corona igniter, for example on its upper side or in its interior. This seal or gasket may be seated, for example, on an annular shoulder of the collar. The corona igniter presses against this seal or gasket when it is inserted into the protective sleeve and screwed to the engine. In this way, improved damping of engine-related vibrations is achieved. This seal or gasket may be realized, for example, in the form of an O-ring or a sealing lip.
The collar preferably features a ventilation bore. Positive or negative pressure in the spark plug shaft can be compensated by means of this ventilation bore.
According to another advantageous refinement of this disclosure, the protective sleeve, particularly the collar and the tubular section, is made of plastic, e.g., polyamide. The collar and the tubular section are preferably realized in one piece, for example, in the form of an injection-molded part. In this way, the protective sleeve has an advantageously low weight and can be cost-efficiently manufactured.
The protective sleeve may be dimensioned in such a way that a continuous annular gap is formed between the protective sleeve and the wall of the spark plug shaft. Furthermore, a continuous annular gap is preferably also formed between the corona igniter and the tubular section. In this case, the engine, the protective sleeve and the corona igniter form a system, the components of which are adapted to one another.
The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.
The protective sleeve 3 comprises a collar 6 for being supported on the edge of the spark plug shaft opening and a tubular section 7 for being inserted into the spark plug shaft of the internal combustion engine 2. In the installed state, the collar 6 is located outside the spark plug shaft whereas the tubular section 7 surrounds the corona igniter within the spark plug shaft.
The spark plug shaft of the engine 3 comprises different sections with different widths. These sections comprise a threaded section 8, into which the corona igniter 1 is screwed, as well as a lower and an upper cylindrical section with different diameters, which may be connected by a conical transition section. The tubular section 7 of the protective sleeve 3 is located in the upper and the lower cylindrical section of the spark plug shaft. The tubular section 7 of the protective sleeve 3 therefore has two cylindrical sections, wherein these cylindrical sections are connected by a transition section that, for example, may have a conical shape.
The underside of the collar 6 of the protective sleeve 3 may carry a seal 9 or gasket, for example an O-ring or a sealing lip. In the installed state, this seal 9 or gasket rests against the edge of the spark plug shaft opening and seals a gap between the collar 6 and the edge of the spark plug shaft opening. The seal 9 or gasket may be seated, for example, in an annular groove on the underside of the collar 6.
The collar 6 may carry a seal 4 for sealing an annular gap between the protective sleeve 3 and the corona igniter 1, for example on its upper side. The seal 4 may be realized, for example, in the form of an O-ring or a sealing lip. The collar 6 may feature an annular shoulder, on which the seal 4 is seated.
The collar 6 may feature a ventilation bore 5 in order to allow a pressure compensation between gas in the spark plug shaft and the surroundings as heating or cooling occurs.
The protective sleeve 3 may be made of plastic and realized, for example, in the form of an injection-molded part. The plastic may be a glass fiber reinforced plastic, e.g., a glass fiber reinforced polyamide.
While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 113 570.4 | Jul 2016 | DE | national |
