Internal-combustion engines – Combustion chamber means having fuel injection only – Injected fuel spraying into whirling fluid
Reexamination Certificate
2000-06-21
2002-10-22
Mancene, Gene (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Injected fuel spraying into whirling fluid
C123S302000, C123S306000, C123S308000
Reexamination Certificate
active
06467454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a spark-ignition type internal combustion engine.
2. Description of Related Art
Internal combustion engine development is aimed at reducing exhaust-gas and noise emissions and lowering fuel consumption. Presently, the diesel type internal combustion engine has better fuel consumption than spark ignition engines. However, the spark-ignition type engine has advantages over the diesel engine, particularly with regard to particle and noise emission. It also has a higher specific power output potential.
Conventionally, the engine's combustion chamber is supplied with a homogeneous stoichiometric or rich fuel/air mixture so that the fuel/air mixture is ignited by the spark plug at the desired ignition point. Typically, during part-load operation the quantity of fuel and air are reduced by throttling. Throttling losses result in higher fuel consumption in a spark ignition engines than in a diesel engine. A diesel engine normally operates with a leaner fuel/air mixture than a spark ignition engine. It is desirable to provide a mixed operating mode in a spark ignition type engine to achieve both high torque characteristics and high power output. Thus, during a lower and medium speed range of engine operation a stratified-charge mode is desirable combined with a largely unthrottled air supply strategy. During a higher-load and higher speed range of engine operation, a homogeneous stoichiometric fuel/air mixture is desirable.
To produce a homogeneous stoichiometric fuel/air mixture desired for a higher-load and higher speed range of engine operation, fuel injected directly into the combustion chamber must be introduced at an early stage in the cycle, even as early as the latter portion of the intake suction portion of the engine cycle. Resultantly, the energy and volume of the air intake is utilised efficiently to create a high mean pressure and therefore a high torque characteristic. To produce a stratified-charge mode desired for a lower and medium speed range and part load mode of engine operation, fuel injected directly into the combustion chamber may be introduced into the combustion chamber relatively late during the compression portion of the engine cycle.
In normal operation or practice, vehicle engines are usually operated in a part-load and medium speed operational range. Therefore, a characteristic map or chart of engine operations should coincide with the characteristics associated with operation under a stratified-charge mode with its advantageous fuel consumption characteristics. However, there are good reasons to limit the operation in the stratified-charge mode of operation. For example, operation with a mean indicated pressure higher than about four bar can produce increasing emissions of soot particles. This occurs because there is insufficient time for complete evaporation under operation involving a large mass of fuel. Accordingly, the maximum useful operational range for stratified-charge characterised by a relatively late fuel injection is limited by speed and load variables. Furthermore, high exhaust-gas recirculation rates are necessary in order to lower the raw emissions of nitrogen oxides during engine operation in these relatively high speed and load ranges. High exhaust-gas recirculation rates leads, in turn, to increased hydrocarbon emissions and to a rise in fuel consumption.
In engines with direct injection of fuel, there are three combustion processes or methods available. A distinction is made between the three basic patterns which are: a jet-controlled method; a wall-controlled method; and an air-controlled method. Several factors are important with all three methods as follows: the properties of the fuel injector or jet; the geometry of the combustion chamber; and the air charge movement.
The jet-controlled method is characterised by a close spatial relationship between the fuel injector and the spark plug or plugs. The cloud of fuel injected into the combustion chamber forms a relatively compact area or zone, to which a quantity of air is introduced. Typically, the movement of the air is in a swirling pattern about an axis of the engine cylinder. The spatial arrangement of the fuel injector and the spark plug or plugs in the combustion chamber must be coordinated carefully to control the stratification profile.
With the wall-controlled method, the fuel/air mixture is formed and controlled by utilising adhesion of fluid to the walls of the combustion chamber and cylinder combined with subsequent separation.
The air-controlled method is based on the principle of transporting injected fuel to the spark plug by the movement of the air charge into the combustion chamber while at the same time actively mixing the air into the fuel cloud. The objective is to achieve a flattening of the stratification profile, so that formation of an extensive rich mixture zone is prevented.
In all three methods, essential factors for good part load and medium speed operation are: the charge movement; the air movement; the characteristics of any recirculated exhaust gas; and turbulence generation. At low engine speeds, an insufficient movement of the charge leads to an inadequate state of mixture preparation because of relatively low velocity between the inlet air flow and the flow from the injector. This typically produces increased emissions of carbon monoxide, hydrocarbons and soot.
The reference, JP-A
62-48927
, discloses a spark-ignition internal combustion engine which has two inlet valves for each cylinder and with separate inlet passages leading to each valve. The first passage is orientated with respect to the combustion chamber to lead thereto in an essentially straight path and the second passage is oriented with respect to the combustion chamber to produce an air swirl pattern. A regulating valve associated with the first passage can be closed during a part-load range or engine mode to produce a swirl pattern of the intake air. By this method of intensifying and directing the air flow, the engine can be operated in a lean fuel/air mixture mode. Furthermore, in this mode the emissions of carbon monoxide, hydrocarbons and soot are markedly reduced. Furthermore any increase in nitrogen oxide emissions as a result of the intensified combustion can be compensated by increasing the degree of exhaust-gas recirculation. In a higher part-load or speed range using an essentially homogeneous charging process with a lean fuel/air mixture or an air ratio equal to one and using substantial exhaust-gas recirculation, the objective is to gain a relatively high charge movement so that a dilution tolerance with an air ratio &lgr;>1.5 can be obtained.
SUMMARY OF THE INVENTION
The primary object of the invention is to achieve a desirable charge movement over a wide speed range and/or load range of the engine along with a low-throttle loss part-load range.
According to the invention, a charger mechanism includes a connecting duct or passage between the first and the second passages. A regulating device is arranged in the connecting duct to apportion the air charge through the two inlet passages according to operating parameters. In this embodiment, the controlled air charge is utilised not only to raise the power output of the engine, but also to intensify and control charge movement. As a result, the engine operating range utilising the advantageous stratified charge mode is enlarged, especially into the upper part-load operating range or mode. Accordingly, it covers wider ranges of the useful driving conditions.
The intensification of the charge movement tends to inhibit undesirable knocking behaviour of the engine. Furthermore, due to the higher mass throughput under part load and consequently lower throttling, the dynamic response behaviour of the engine is appreciably improved, particularly as compared to an engine utilising intake manifold injection rather than direct injection. In a direct injected engine, the increased mass throughput can be utilised with little or no throttling and is not
Fledersbacher Peter
Sumser Siegfried
Wirbeleit Friedrich
Castro Arnold
Crowell & Moring LLP
Daimler-Chrysler AG
Mancene Gene
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