Internal-combustion engines – Combustion chamber means having fuel injection only – Having a particular relationship between injection and...
Reexamination Certificate
2001-06-02
2003-06-03
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Having a particular relationship between injection and...
C123S298000, C123S302000, C123S275000
Reexamination Certificate
active
06571764
ABSTRACT:
This invention relates to a direct injection internal combustion engine having per cylinder at least one intake valve, at least one exhaust valve, a more or less coaxial ignition device, an injection valve, and a piston with a combustion chamber trough, the injection valve being mounted on the intake side.
This invention also relates to a process for mixture preparation and combustion in such direct injection internal combustion engine.
Publication DE 197 41 380 A1 discloses a generic reciprocating internal combustion engine with direct fuel injection by a separately mounted fuel injection nozzle. This internal combustion engine has a tent shaped piston head and a tent shaped cylinder cover. Mounted in the piston head is a central rooflike extension which extends more or less symmetrically above the two rooflike surfaces of the piston head. A fuel injection nozzle which ends in the combustion chamber at a very small angle is mounted in the cylinder cover between the gas intake valves.
With this state of the art taken as a basis, it is the object of this invention to design an improved direct injection internal combustion engine and a process for mixture preparation and combustion, a process characterized by low fuel consumption in uniform lean-mixture operation and in stratified lean-fuel operation by low fuel consumption and low exhaust emissions.
In order to solve this problem the center of the combustion chamber trough in the piston is noticeably displaced toward at least one discharge valve opposite the axis of the cylinder and the boundary wall of the combustion chamber trough on the intake side extends in a projection along the axis of the cylinder between the ignition device and the injection valve. As a result of this design of the combustion chamber trough the mixture is prepared inside the combustion chamber with particularly great efficiency and combustion is characterized by low pollutant values. For this purpose the fresh air entering the combustion chamber in tumble flow through the intake openings controlled by the adjacent intake valves and flowing downward toward the piston on the cylinder wall opposite the intake valves and the fuel, which is injected through the injection valve earlier or later, depending on the operating condition of the internal combustion engine, is uniformly mixed by means of the combustion chamber trough displaced toward the discharge side, or alternatively is prepared as a stratified charge and by means of the boundary wall of the combustion chamber trough is deflected near the axis of the cylinder toward the ignition device and is ignited there. Hence the prepared mixture is moved directly from the combustion chamber trough to the ignition device, and not first guided along the cylinder wall and/or the top of the combustion chamber before finally reaching the ignition device.
In order to sustain the fresh air tumble flow, when there are two intake valves the centers of the disks of the intake valves should, in accordance with an advantageous development of the invention, be positioned a maximum distance from each other and in the closed position be positioned a minimum distance from the axis of the crankshaft. This feature additionally facilitates mounting of the injection valve between the intake valves.
The intake valve should be mounted at an angle of approximately 30 to 80 degrees to the axis of the cylinder, so that the area of the boundary wall of the combustion chamber trough on the intake side near the axis of the cylinder of the injected fuel can be reached.
In addition, the injection valve should have a central stream axis which extends at an angle of approximately 55 to 70 degrees to the axis of the cylinder, so that the stream is positioned in the combustion chamber at a relatively steep angle to the axis of the cylinder.
For the sake of homogeneous lean operation the injection valve injects fuel into the cylinder during the intake cycle at a crankshaft angle of approximately 380 to 160 degrees, depending on engine speed, before reaching top dead center. Thus fuel is injected more or less in the center of the fresh air flow prevailing in the combustion chamber, so that the fuel and the fresh air may be mixed uniformly.
And for stratified lean operation the injection valve injects fuel into the cylinder during the injection cycle at a crankshaft angle of approximately 120 to 20 degrees, before the piston reaches top dead center. Hence the fuel is injected mostly in advance of the fresh air tumble flow, is stabilized by the fresh air flow in an ignitable charge cloud above the boundary wall near the injection valves, and finally is transported to the ignition device. In the process the boundary wall of the combustion chamber trough on the intake side serves both to guide or concentrate the fresh air tumble flow and to deflect the resulting ignitable mixture cloud.
By preference the width of the combustion chamber trough amounts to approximately two-thirds of the diameter of the piston. As a result, the fresh air tumble flow moving through the combustion chamber trough can be sustained over a large area.
By special preference the combustion chamber trough is mounted displaced so far to the side of at least one exhaust valve that the center of the trough or the center of gravity of its volume is positioned about a third of the diameter of the piston away from the edge of the piston on the outlet side. As a result of this feature, the boundary wall on the exhaust side is positioned on the edge of the piston, so that no large areas of low flow velocities may be formed on the discharge side of the combustion chamber.
If the boundary wall of the combustion chamber trough on the exhaust side near the axis of the cylinder is designed to slope gently toward the head of the piston and the boundary wall of the combustion chamber trough remote from the axis of the cylinder to slope steeply toward the head of the piston, the fresh air flow can enter the combustion chamber trough on the boundary wall on the exhaust side and can be deflected optimally in the direction of the ignition device when emerging from the combustion chamber trough on the boundary wall on the intake side.
So that the fuel stream emerging from the injection valve may reach the combustion chamber without direct wetting of the piston, a small recess is provided in the piston, which recess extends from the boundary wall of the combustion chamber trough on the intake side and is coordinated with the shape of the fuel stream.
The problem posed for this invention is also solved by a process of fuel mixture preparation and combustion in a direct injection internal combustion engine as described in one of claims
1
to
11
. In this process there is formed in the combustion chamber an intensive charge movement, such that the fresh air, initially directed by way of the cylinder wall, enters the combustion chamber trough by way of the boundary wall on the exhaust side, is accelerated toward the center of the combustion chamber trough, and is deflected by the boundary wall of the combustion chamber trough on the intake side, and such that the fuel is injected more or less transversely to the fresh air flow, which in this phase is directed vertically upward.
The process claimed for the invention is characterized among other things also by the fact that the period between the end of injection of the fuel corresponds to approximately 10 to 25 crankshaft angle degrees. Effective mixing of fresh air is definitely ensured over this relatively long period.
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Budack Ralf
Ottowitz Alfred
Rieger Thomas
Serifsoy Murat
Wurms Rainer
Argenbright Tony M.
Audi AG
Harris Katrina
Stevens Davis Miller & Mosher LLP
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