Patent Application
20190376441
This patent disclosure relates generally to internal combustion engines and, more particularly, to a pre-chamber spark plug.
Engines operating using a gaseous fuel are typically operated with a lean fuel mixture. The nature of the gaseous fuel, which is often supplied in an intake manifold of the engine before being distributed into engine cylinders in mixture with incoming or charge air, requires a vigorous spark to ignite when in the engine cylinders. The lean fuel mixture used is often challenging to reliably ignite, and often results in incomplete combustion, misfires, detonation, poor fuel economy and the like. The device typically tasked igniting the lean air/fuel mixture in the cylinder is a spark plug. Spark plugs are used, either alone or within a combustion pre-chamber, to ignite a flame, which then propagates into the cylinder or from the pre-chamber as a burning mass provided into the cylinder.
Pre-chamber, or precombustion chamber spark plugs, are sparking devices used in the precombustion chamber of an engine to enhance the lean flammability limits in lean burn engines such as natural gas lean burn engines. One example of a precombustion chamber spark plug can be seen in U.S. Patent Application Pub. No. 2016/0254650 A1 (“Kuhnert”), which is titled “Prechamber Spark Plug” and which describes a precombustion chamber spark plug in which a ground electrode is embodied as a substantially circular cylindrical pin that can be welded into a passage of the spark plug body.
While precombustion chamber spark plugs are at least partially effective in achieving a more reliable ignition of lean air/gaseous fuel mixtures than traditional, open air spark plugs, it is always desirable to improve reliable ignition within engine cylinders.
The disclosure describes, in one aspect, a spark plug for an internal combustion engine. The spark plug includes a body having a terminal post adapted for connection to a source of electrical potential. A central electrode is electrically connected to the terminal post. A mounting sleeve includes a threaded portion, wherein the central electrode extends at least partially through the mounting sleeve. An internal insulator is disposed between at least a portion of the central electrode and the mounting sleeve. A precombustion cavity is defined partially within the body and between the mounting sleeve and the threaded portion, wherein a free end of the central electrode extends into the precombustion cavity. A plurality of posts is disposed through the mounting sleeve at the threaded portion, each of the plurality of posts protruding at least partially into the chamber by a predetermined distance (d). An electrode having one or more limbs is connected to the free end of the central electrode, each of the one or more limbs extending into the precombustion cavity and being disposed at a respective gap from a corresponding one of the plurality of posts, each respective gap having a predetermined length (D). A cap is disposed to close an open end of the precombustion cavity, the cap being connected to the threaded portion and having a cupped end forming one or more openings.
In another aspect, the disclosure describes a spark plug for an internal combustion engine. The spark plug includes a body having a centerline extending along an axial direction, the body including a terminal post adapted for connection to a source of electrical potential. A central electrode is electrically connected to the terminal post. A threaded portion is connected to the terminal post via a mounting sleeve, the threaded portion forming a bore having an open end opposite the terminal post in the axial direction. A precombustion cavity is defined in the body in an area opposite the terminal post and within and occupying the bore in the threaded portion. A cap is connected to the threaded portion and closes the open end. A free end of the central electrode extends into the precombustion cavity and is connected to an electrode having one or more limbs, each of the one or more limbs extending into the precombustion cavity. A plurality of posts is disposed through the threaded portion and protrudes into the chamber by a predetermined distance (d). Each of the plurality of posts is disposed at a respective gap from a corresponding one of the one or more limbs, each respective gap having a predetermined length (D).
The present disclosure is applicable to internal combustion engines and, more particularly, to engines operating with a gaseous fuel, which may or may not additionally include a precombustion chamber that is separate from a main combustion chamber and also separate from any cavities formed within the body of a spark plug disposed in communication with the engine combustion chamber, as described below. The spark plug in accordance with the disclosure can be used either within a precombustion chamber of an engine, or directly into a main combustion chamber of the engine, for reliably igniting a mixture of air with a gaseous fuel within an engine combustion and/or precombustion chamber.
A center electrode 114 is electrically connected to the terminal post 102 and extends through the spark plug 100 and into a precombustion chamber portion 116. During operation, an electrical potential provided through the terminal post 102 is transferred through the spark plug 100 and onto an internal terminal, which provides a spark when grounded to the engine via the threaded portion 112, in the typical fashion. The center electrode 114 is electrically insulated from the mounting sleeve 110 and from the threaded portion 112, which constitutes the mating ground electrode for the spark plug 100. The center electrode 114 is connected to a sparking electrode assembly 118, which is suspended within a precombustion chamber 120 defined within the precombustion chamber portion 116 of the spark plug 100. Ground electrode posts 122 are embedded into the sidewalls of the precombustion chamber 120 and extend by a distance, d, into the precombustion chamber 120 such that the posts 122 are at a predefined, gap distance D from tips formed at the free ends of branches 124 of the sparking electrode assembly 118.
In the present disclosure, the phrase “precombustion chamber” is used to refer to the cavity denoted by reference numeral 120 in the figures, but it should be appreciated that this nomenclature does not and need not refer to a precombustion chamber or “prechamber” of an engine; the spark plug 100 may be used directly in fluid contact with a main combustion chamber of an engine in place of a non-precombustion or “open spark” plug, and may alternatively be used within a precombustion chamber of an engine, which would place the spark plug 100 in indirect fluid contact with the engine's main combustion chamber.
The precombustion chamber 120 or, simply, the chamber 120, is formed as a generally cylindrical cavity within a hollow cylindrical wall that is formed as part of a body of the spark plug 100 within the threaded portion 112 and extending axially above and below the threaded portion 112 such that a volume of the chamber 120 is maximized. In the embodiment illustrated in
In the embodiment shown in
Certain alternative embodiments of the spark plug 100 are shown in
In a first alternative or second embodiment of the spark plug 100 is shown in
Another or a third embodiment for the spark plug 100 is shown from two different perspectives in cross section in
As shown in
This disclosure generally relates to internal combustion engines and, more specifically, to one or more embodiments for sparkplugs for use with engines operating with a gaseous fuel, which can be used alone or in addition to other fuels such as diesel to operate the engine in at least some operating conditions. The gaseous fuel used to operate the engine may be natural gas, liquefied petroleum gas (LPG), biogas, or any other combustible fuel, which is provided upstream of an engine cylinder, in mixture with air, or directly into the cylinder of the engine.
In certain engines operating with gaseous fuel, and air/fuel mixture or ratio that is provided in the engine cylinders may be lean, and ignition may be provided by a spark that is generated within a chamber in the presence of a combustible mixture containing air and fuel. A burning combustible mixture that is ignited within the chamber is then provided through openings into the main combustion chamber of the engine to propagate a flame and complete the burning of fuel within the engine combustion chamber. The embodiments for spark plugs described herein are advantageously constructed to maximize the volume or internal cavity size of the chamber to provide a more reliable ignition under a variety of engine operating conditions such as conditions of low ambient temperature, high altitude and others, in which reliable combustion under existing spark plug configurations may not generally be as reliable.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
