Internal-combustion engines – Combustion chamber means having fuel injection only – Air entering combustion chamber through plural inlets
Reexamination Certificate
1999-12-13
2001-06-12
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Air entering combustion chamber through plural inlets
C123S305000, C123S308000, C123S432000
Reexamination Certificate
active
06244246
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a stratified charge spark ignition internal combustion engine.
BACKGROUND OF THE INVENTION
International Patent Application No. PCT/GB98/02292 describes a fuel fractioning system capable of separating the fuel into at least two continuous streams of fuel fractions having different octane ratings.
International Patent Application No. PCT/GB98/02754 describes an engine specifically designed to take advantage of the availability of two streams of fuel fractions having different octane ratings. In the latter engine, the intake system is designed such that the different fuel fractions reside in different regions of the engine combustion chambers. During high load operation, the higher octane fuel fraction is concentrated in the end-gas region remote from the spark plug with the aim of extending the knock tolerance of the engine and thereby allowing the compression ratio of the engine to be increased.
International Patent Application No. PCT/GB98/00614 describes another engine designed to take advantage of the availability of two streams of fuel fractions having different octane ratings in which the intake system is designed to promote stratification of the fuel fractions within the combustion chambers. In this case, it is the lower octane fuel fraction that is concentrated in regions remote from the spark plug with the aim of achieving controlled auto ignition under low and medium load operating conditions in order to minimise NOx emissions.
British Patent Application No. 9802766.7 describes an engine that combines the benefits of the above two proposals. The engine in this case has two-position swirl control valves in its intake ports and each combustion chamber has a single spark plug. The two-position swirl control valves serve to provide two stratified charge patterns of the fuel fractions in relation with the single spark plug such that in one position, for high load operation, the higher octane fuel fraction is concentrated in the periphery region of the engine combustion chamber in order to suppress knock and in the other position, for low and medium load operations, the lower octane fuel fraction is concentrated in the periphery region of the engine combustion chamber in order to promote controlled autoignition.
OBJECT OF THE INVENTION
The present invention seeks to provide an alternative engine design that takes advantage of the availability of continuous supplies of fuel fractions having different octane ratings to improve knock tolerance during high load operation and promote auto ignition during low and medium load operation.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a spark ignition internal combustion engine having a fuel supply system for separating the fuel into two or more continuous streams of fuel fractions having different octane ratings, an intake system operative to create within each combustion chamber a stratified charge comprising at least two regions each containing a higher concentration of respective one of the fuel fractions, at least two spark plugs in each combustion chamber each spark plug being located in a respective one of the stratified charge regions and an ignition system for separately controlling the spark timings of the spark plugs to vary the pattern of flame propagation through the stratified charge in the combustion chambers in dependence upon the engine operating conditions.
In the invention, the stratification geometry of the fuel fractions can be fixed, avoiding the need for flow regulators or diverters in the intake system. Instead, the relative spark timing is used to control the flame propagation pattern to position the end gas in the lower or higher octane regions of the stratified charge to suit the operating conditions.
Thus, if under high load operation the spark plug in a lower octane fuel fraction region is fired first, the flame will spread from the lower octane region and will burn last in the higher octane region to reduce the tendency to knock. Conversely, if under low and medium load operating conditions the spark plug in the higher octane fuel fraction region is fired first, then the flame will spread from the higher octane fraction and will burn last in the lower octane fraction to promote auto ignition of the lower octane fraction and thereby reduce NOx emissions.
It is possible to initiate combustion from a single one of the spark plugs, but it is preferred to fire both spark plugs in each combustion cycle and to vary the relative spark timing of the spark plugs in dependence upon engine operating conditions.
In calculating the optimum spark timings for the two spark plugs for any given set of operating conditions, it is preferred not only to take engine load into account but also to take into consideration other parameters affecting flame propagation, such as mixture strength and EGR content of the different regions of the stratified charge. It is further possible to control the composition of the charge in the different regions in order to maximise the benefit achieved by the independent spark timings.
In a preferred embodiment of the invention, each combustion chamber of the engine has two intake valves and one exhaust valve arranged on the opposite side of the combustion chamber in the plane of symmetry which passes between the two intake valves. In this case, the two fuel fractions may be supplied separately through the two intake valves to form a stratified charge with the fuel fractions lying on opposite sides of the plane of symmetry. The two spark plugs in such an engine may conveniently be located one on each side of the plane of symmetry so that they lie in the halves of the engine cylinder containing the different fuel fractions.
The advantage of the invention is that the same stratified charge pattern of the fuel fractions can be maintained throughout the engine operating range while different combustion modes are selected. This eliminates the need for a switching device for the air or fuel flow which will otherwise be necessary in order to change the stratified charge pattern to suit the different combustion modes. In this invention, switching of the combustion mode is achieved quickly and reliably by simply switching the first firing pulse from one spark plug to another.
Engines are known that have two spark plugs per cylinder but in the known engines no special steps are taken to create a stratified charge containing different fuel fractions ignited by the different spark plugs. In the known engines, the combustion charge is homogeneous and the two spark plugs are fired simultaneously to improve the probability of ignition by providing two ignition sources, and to shorten the combustion period by creating two flame propagation kernels.
REFERENCES:
patent: 4688532 (1987-08-01), Hasegawa
patent: 5111791 (1992-05-01), Onodera
patent: 5379743 (1995-01-01), Stokes et al.
patent: 5529038 (1996-06-01), Tsuchida
patent: 5799638 (1998-09-01), Tsuchida et al.
patent: 5894826 (1999-04-01), Jaye
patent: 6125817 (2000-10-01), Piock et al.
patent: 6135088 (2000-10-01), Duret
patent: 3224337 C1 (1983-10-01), None
patent: 19854923 A1 (1999-06-01), None
patent: 0390589 A2 (1990-10-01), None
patent: 0594462 A1 (1994-04-01), None
patent: 2278915 (1976-02-01), None
patent: 2298896 (1996-09-01), None
Ford Global Technologies Inc.
Huynh Hai
Kamen Noah P.
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