Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2002-07-22
2004-10-05
Huynh, Hai (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S301000, C123S302000, C123S305000, C123S279000, C123S568110
Reexamination Certificate
active
06799551
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a direct-injection internal combustion engine wherein a fuel is injected into a combustion chamber, and more particularly to techniques for stratifying an intake gas charge within the combustion chamber.
BACKGROUND ART
First Prior Art (JP-A-11-148429)
This prior art proposes a technique for stratifying an intake gas charge within a combustion chamber of a direct-injection type compression-ignition internal combustion engine provided with an exhaust gas recirculating (EGR) device, so that the amounts of harmful substances left in the exhaust gas are reduced by the stratification of the intake gas charge.
The combustion chamber is provided with two intake ports through which respective swirl flows are formed concentrically with each other in the same direction. The intake port located upstream of the swirl flows is provided to form the swirl flow of a small diameter in a central portion of the combustion chamber, while the intake port located downstream of the swirl flows is provided to form the swirl flow of a large diameter in a peripheral portion of the combustion chamber.
A recirculated exhaust gas is mixed with the intake gas flowing through the upstream intake port, but is not mixed with the intake gas flowing through the downstream intake port, so that the intake gas existing in a cylindrical region in the central portion of the combustion chamber contains the recirculated exhaust gas, while the intake gas existing in an annular region in the peripheral portion of the combustion chamber does not contain the recirculated exhaust gas.
This prior art says that the swirl flows of small and large diameters are formed in the respective radially inner and outer portions of the combustion chamber. The swirl flow, however, has a centrifugal force increasing its diameter. The swirl flow of the small diameter expands radially outwardly due to a centrifugal force thereof, with an increase of its diameter, and eventually collides and mixes with the swirl flow of the large diameter an increase of which is prevented by the cylindrical wall of the combustion chamber. Accordingly, it is difficult to stratify the intake gas charge within the combustion chamber such that the intake gas containing the recirculated exhaust gas exists in the central cylindrical region while the intake gas not containing the recirculated exhaust gas exists in the peripheral annular region.
Even if the swirl flows of small and large diameters are formed in the respective radially inner and outer portions of the combustion chamber in the intake stroke, there arises a squish flow of the intake gas from a squish area over a peripheral portion of the top face of the piston into a cavity in a central portion of the top face of the piston, in the subsequent compression stroke. The swirl flow of the large diameter in the peripheral portion of the combustion chamber is brought by the squish flow into the central portion of the combustion chamber, and collides and mixes with the swirl flow of the small diameter in the central portion of the combustion chamber. Therefore, it is difficult to maintain, up to a point of time near a terminal period of the compression stroke, the radially stratified state which has been established in the intake stroke and in which the intake gas charge consists of the inner cylindrical swirl flow and the outer annular swirl flow.
Thus, the present prior art arrangement does not assure that at a point of time near the terminal period of the compression stroke at which the combustion of the fuel injected into the combustion chamber is initiated, the central cylindrical region and the peripheral annular region of the combustion chamber are respectively charged with the intake gas containing the recirculated exhaust gas and the intake gas not containing the recirculated exhaust gas, or the intake gases having high and low concentration values of the recirculated exhaust gases, namely, the two intake gases of different compositions. It is not clear whether the amounts of harmful substances left in the exhaust gas are reduced.
The combustion of the fuel within the combustion chamber cannot be controlled as desired, unless the intake gas charge within the combustion chamber is stratified as needed, at the time of initiation of the fuel combustion.
Second Prior Art (
FIG. 16
)
A direct-injection type internal combustion engine of premixing type has an ordinary fuel injector
2
disposed in a center portion of the top surface of a combustion chamber
1
, and a plurality of premixing fuel injector
31
which are disposed at respective positions in a peripheral portion of the top surface of the combustion chamber
1
and each of which is arranged to inject a fuel in a direction that is slightly inclined downwards with respect to the top surface of the combustion chamber. The plurality of premixing fuel injectors
31
are operated at a premixing fuel-injection timing before 30° BTDC during the intake stroke or compression stroke, to inject a portion of a required amount of fuel. And the ordinary fuel injector
2
is operated to inject the remaining portion of the required amount of fuel, at a normal fuel-injection timing during the terminal period of the compression stroke.
This prior art makes it possible to reduce the amount of a portion of the fuel injected from the premixing fuel injectors
31
at the premixing fuel-injection timing, which portion adheres to the wall surfaces of the cavity of the combustion chamber
1
. It is therefore possible to reduce the amounts of production of HC (hydrocarbon), SOF (soluble organic fraction) and white smoke due to quenching near the wall surfaces of the cavity.
Although the amount of HC and the like to be produced due to the adhesion of the premixing fuel to the wall surfaces of the cavity of the combustion chamber is reduced, the amount of HC and the like to be produced due to the fuel existing in the squish area of the combustion chamber is not reduced. Thus, the present prior art is not so effective to reduce the amount of HC and the like left in the exhaust gas.
The present prior art requires a plurality of premixing fuel injectors to be disposed in the peripheral portion of the top surface of the combustion chamber, in addition to the ordinary fuel injector disposed in the center portion of the top surface. Accordingly, the construction of the engine is complicated.
Third Prior Art (JP-B-2906932)
A lean-burn type spark-ignition internal combustion engine uses a plurality of intake ports through which two or three tumbling flows of intake gas are formed in the same direction, in respective right and left portions or respective right, left and central portions of the combustion chamber, during the intake stroke. A fuel is injected into only the intake port for forming the tumbling flow that passes a spark plug disposed on the top surface of the combustion chamber.
In this prior art, the tumbling flow of the intake gas containing the fuel does not pass the entirety of the squish area of the combustion chamber, but passes only a portion of the squish area, so that the amount of the fuel existing in the squish area of the combustion chamber is reduced, whereby the amount of production of HC and the like due to quenching in the squish area is reduced.
Although the fuel does not exist in a portion of the squish area that the tumbling flow of the intake gas not containing the fuel passes, the fuel exists in a portion of the squish area that the tumbling flow of the intake gas containing the fuel passes. In this respect, the present prior art is not effective enough to reduce the amount of the fuel existing in the squish area of the combustion chamber, and is therefore not effective enough to reduce the amount of production of HC and the like due to quenching in the squish area.
DISCLOSURE OF THE INVENTION
Study Relating to Stratification of Intake Gas Charge within Combustion Chamber
1) In a direct-injection type compression-ignition internal combustion engine, a jet of a fuel injected from the fuel injector into t
Akihama Kazuhiro
Fuyuto Takayuki
Hotta Yoshihiro
Inagaki Kazuhisa
Inayoshi Minaji
Huynh Hai
Kabushiki Kaisha Toyota Chuo Kenkyusho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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