Internal-combustion engines – Combustion chamber means having fuel injection only – Injection of fuel onto igniter – deflector – heater – or atomizer
Reexamination Certificate
1999-06-11
2001-01-09
Kwon, John (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Injection of fuel onto igniter, deflector, heater, or atomizer
C123S295000
Reexamination Certificate
active
06170458
ABSTRACT:
BACKGROUND
In general, a spark plug includes an outer shell and an insulative core. At a firing end of the spark plug, a firing electrode extends from the insulative core and a ground electrode extends from the outer shell. The two electrodes define a spark gap between them. In a combustion engine, a spark formed in the gap is used to ignite a mixture of fuel and air.
In conventional two- and four-stroke combustion engines, a combustible fuel from a fuel injector or carburetor is mixed with air in the intake. When the intake valve or port opens, a fuel vapor, consisting of fuel and air, is pulled by negative pressure into the combustion chamber where it dissipates throughout the chamber. A spark at the spark plug ignites the fuel vapor, causing rapid expansion of the chamber contents and corresponding displacement of a piston.
A recent modification to the conventional combustion engine is the gasoline direct injection (GDI) engine. A defining characteristic of the GDI engine is the injection of fuel as a liquid. A second defining characteristic is the introduction of fuel and air into the combustion chamber through separate ports. Thus, rather than injecting a fuel vapor consisting of fuel and air, the combustible fuel is injected under pressure as a liquid through a fuel intake port and air is introduced through an air intake port, both of which open into the combustion chamber.
The fuel is sprayed as a liquid directly in the direction of the spark gap. The spray spreads out from the fuel intake port in the shape of a cone (i.e., a spray cone) with the central longitudinal axis of the spray cone aimed at the spark plug gap. A small percentage of the fuel vaporizes and mixes with the air injected into the chamber through the air intake port. By aiming the central longitudinal axis of the spray cone directly at the spark plug gap rather than attempting to fill the entire chamber with a combustible fuel vapor, less combustible fuel is needed to create a suitable displacement of the piston. A spark ignites the fuel during the brief period in which the fuel surrounds the spark plug gap, rather than at a later period in which the fuel would have dispersed to fill the entire chamber. Reduced fuel usage also results in a reduction in polluting emissions.
In GDI engines, the fuel is injected into the combustion chamber at different stages in the compression stroke depending upon speed. At low speeds the fuel is injected late in the stroke while at high speeds the fuel is injected early in the stroke. At low speeds, because of the high compression in the chamber resulting from the late stage of the compression stroke, the cone of fuel sprayed at the gap does not rapidly disperse throughout the chamber. Instead, the flow pattern of the spray cone is not substantially altered as it moves toward the gap. At high speeds, the fuel is injected when there is less compression and different flow patterns in the chamber. These differences cause the fuel to mix throughout the chamber.
In two-stroke GDI engines the fuel is injected during each cylinder compression stroke whereas in four-stroke GDI engines the fuel is injected during alternating cylinder compression strokes.
Although a direct injection (DI) engine may be operated using gasoline, as described above, other combustible fuels, such as alcohol, may be used. Moreover, while the combustible fuel may be injected in the combustion chamber in the form of a spray cone of fuel, it also may be injected as a stream of fuel or in other variations or shapes.
SUMMARY
In one general aspect, the invention features a DI combustion engine having a combustion chamber with a fuel intake port, an air intake port, a spark plug insertion opening and a spark plug inserted in the insertion opening. The spark plug includes a firing electrode, a ground electrode, and an insulator core nose that extends into the chamber when the spark plug is inserted in the opening. A shield is positioned between the fuel intake port and the opening and is configured to reduce the flow of fuel from the fuel intake port to the insulator core nose without preventing the flow of fuel to a spark plug gap defined between the firing electrode and the ground electrode.
Embodiments may include one or more of the following features. For example, the shield may be permanently, semi-permanently, or threadably attached to a surface of the chamber. The shield may be threadably inserted from outside the chamber, such as through a threaded channel passing through a wall of the chamber. The shield also may be attached to the spark plug and may be in the form of a thin rod or a skirt that partially or fully encircles the circumference of the insulator nose core. By reducing the flow of fuel from the fuel intake port to the spark plug insulator core nose, the shield protects the insulator from fouling, which is a build up of deposits that may impact plug life. The shield may be made of a metal, such as nickel or a nickel alloy, or ceramic material with thermal properties suitable for placement in the head of the combustion chamber. In the various embodiments, the shield extends from the surface a sufficient length to protect the insulator core nose but not an excessive length so as to block the fuel from reaching a spark gap between the firing electrode and the ground electrode.
An additional general aspect of the invention features the ground electrode configured to minimize the obstruction to fuel flow when the ground electrode is aligned between the fuel intake port and the firing electrode. The ground electrode may have a round shape or a shape resembling an air foil. Such a shape enhances the ability of a vapor portion of the injected fuel to flow around the ground electrode to reach the spark gap when the ground electrode is aligned in front of the injection port. The ground electrode has a rectangular firing surface to improve spark performance and the ability to attach a precious metal to the firing surface. A precious metal may be attached to the firing surface to lengthen gap life and improve spark plug performance.
Conventional spark plugs perform optimally in DI engines when the plug is aligned such that the ground electrode does not obstruct the path of fuel flow from the fuel injection port to the gap. The rounded or air-foil-shaped ground electrode provides an inexpensive and effective means of reducing the impact of plug alignment on engine performance. Moreover, the rounded or air-foil-shaped ground electrode is implemented with the protective shield to further improve spark plug performance.
The invention also provides a technique for improving engine performance. In one general aspect, a shield positioned between the injection port and the insulator core nose of a spark plug protects the insulator from fouling, which is a build up of deposits that may affect the spark gap and impact plug life. The shield may be attached to the cylinder head or may be a component of the spark plug.
Other features and advantages will be apparent from the following description, including the drawings, and from the claims.
REFERENCES:
patent: 2878299 (1959-03-01), Starr
patent: 4014300 (1977-03-01), Klomp
patent: 4232638 (1980-11-01), Takahashi et al.
patent: 5650687 (1997-07-01), van den Bogaert
patent: 196 27 524 A1 (1998-01-01), None
patent: 0 831 213 A2 (1998-03-01), None
Cooper Automotive Products, Inc.
Kwon John
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
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