Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2002-03-28
2004-02-03
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S280000, C060S285000
Reexamination Certificate
active
06684630
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a direct-injection, spark-ignition engine having a turbo-charging device.
BACKGROUND OF THE INVENTION
Recent environmental requirements have necessitated improvements in fuel efficiency of automotive spark-ignition engines to improve energy savings and reduce CO
2
(carbon-dioxide) emissions. Under these requirements, a direct-injection, spark-ignition engine has been recently developed wherein fuel is directly injected into the combustion chamber to collect for stratification in the vicinity of the spark plug, for enhancing ignitionability, while causing the air-fuel ratio to have a lean stoichiometric air-fuel ratio for improving fuel efficiency.
An engine having a turbo-charging device which attains the increase in engine output by means of high intake-pressure, or high charging-efficiency caused by the efficient use of the high exhaust-gas pressure in the automotive engine, is also known. Such an engine has been noted in recent years for its effectiveness in providing a leaner air-fuel ratio.
Normally, a catalyst converter adopting an exhaust-gas purification catalyst is disposed in an exhaust-gas passage of an engine. The catalyst purifies pollutants such as NOx (nitrogen-oxides), HC (hydrocarbon), and CO (carbon-monoxide) included in the exhaust gas emitted from the combustion chamber of the engine of the automobile. The exhaust-gas purification catalyst generally has sufficient purification for an exhaust-gas having a temperature higher than its activation temperature and insufficient purification for the exhaust-gas having a lower temperature than the activation temperature.
Accordingly, when the engine starts in a cold state, the exhaust-gas purification catalyst is not activated for a certain time period after the engine starts. To reduce pollutants immediately after a cold start, the exhaust-gas purification catalyst is required to rise in temperature rapidly to attain early activation.
In an engine having a turbo-charging device, however, a turbine of the turbo-charging device is disposed in the exhaust-gas passage, and the catalyst converter is disposed downstream of the turbine. With this arrangement, there is a problem that the temperature rise, or the activation of the exhaust-gas purification catalyst, is delayed in cold-start because the turbine cools the exhaust gas to, for example, 100° C. To avoid this problem, the catalyst converter may be arranged upstream of the turbo-charging device. In this case, however, the catalyst converter is located immediately downstream of the combustion chamber, so that the exhaust-gas purification catalyst is unduly heated when the engine is fully heated, causing the problem of degradation in its durability due to the heat. In addition, the flow resistance due to the catalyst converter being located upstream of the turbine inevitably causes turbo lag, which impairs acceleration response in the turbo-charging device.
In view of the above problems, numerous solutions have been proposed. One such approach is a supercharged engine which lowers its turbine rotational speed during cold start to suppress heat transmission from the exhaust gas to the turbine for promoting temperature rise or activation of the exhaust-gas purification catalyst. See, Japanese Patent Publication No. H9-100724.
Another approach is disclosed in Japanese Patent Publication No. H10-212987, wherein in a direct-injection, spark-ignition engine the fuel being injected is divided in two, or the fuel is injected during the intake stroke and the compression stroke in cold start, to increase the temperature of the exhaust gas for promoting temperature rise or activation of the exhaust-gas purification catalyst.
Another direct-injection spark-ignition engine has been also proposed, in which fuel is injected during the intake stroke and in the compression stroke during a predetermined period after cold start, then fuel is injected in the compression stroke and in the expansion stroke after that period, to increase the temperature of the exhaust gas for promoting temperature rise or activation of the exhaust-gas purification catalyst. See, Japanese Patent Publication No. 2000-120471.
Recently, emission standards for automotive engines have become more strict, requiring the engines to activate their exhaust-gas purification catalysts within approximately 30 seconds after cold start. However, the conventional approaches to promoting activation of the exhaust-gas purification catalyst in cold start, as disclosed in Japanese Patent Publication Nos. H9-100724, H10-212987, and 2000-120471 described above, may be insufficient for promoting the temperature rise or activation of the exhaust-gas purification catalyst under these newer, stricter emission standards. Accordingly, the auto industry seeks more effective approaches for promoting activation of the exhaust-gas purification catalyst.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide an approach to sufficiently promote the temperature rise or activation of the exhaust-gas purification catalyst which is disposed downstream of the turbine in the exhaust-gas passage, in a direct-injection, spark-ignition engine having a turbo-charging device, during cold start.
In accomplishing this and other objectives of the present invention, there is provided a direct-injection, spark-ignition engine having a turbo-charging device. A piston compresses the injected fuel. A fuel injector directly injects fuel into a combustion chamber. An ignition device ignites the injected fuel. An exhaust-gas purification catalyst is disposed downstream of a turbine of the turbo charging device in an exhaust-gas passage. A fuel injection controller controls the amount and the timing of the fuel injection by the fuel injector. An ignition controller controls the ignition timing by the ignition device. An intake-air controller controls the amount of intake-air introduced in the combustion chamber. The fuel injection controller causes the fuel injector to divide fuel injection into a leading fuel injection during a leading period of an intake stroke of the piston prior to the ignition timing, and a trailing fuel injection during a trailing period of an expansion stroke after the ignition timing for a predetermined operating condition, where the exhaust-gas purification catalyst is to be activated. A fuel injection controller controls the fuel injector and the intake-air controller controls the amount of intake-air so that the excess air ratio &lgr; in the combustion chamber is larger than 1, when the combustion of the fuel by the trailing fuel injection and the leading fuel injection completes.
Preferably, at low engine rotational speed and low engine load, the fuel injection controller controls the fuel injector and the intake-air controller controls the amount of intake-air, so that the excess air ratio &lgr; in the combustion chamber is within the range of about 2 to 3 when the fuel of the leading fuel injection combusts.
Accordingly, the fuel injected by the leading fuel injection combusts under high volumetric efficiency (&eegr;v) with a leaner air-fuel ratio of &lgr; of 2 to 3 (this condition is referred to as “a leading combustion”). Additionally, fuel of the trailing fuel injection effectively combusts because of a leaner air-fuel ratio (exhaust-gas air-fuel ratio) of &lgr; smaller than 1 at the combustion (this combustion is referred to as “a trailing combustion”). At this time, the trailing combustion raises the exhaust-gas temperature. Moreover, the turbine of the turbo-charging device agitates the exhaust-gas (this agitation is referred to as “turbine agitation”). The turbine agitation causes unburned HC in the exhaust-gas to oxidize (afterburn), and this exotherm further raises the exhaust-gas temperature. In this manner, exhaust-gas temperature is raised from heat generated by the trailing combustion and by the oxidization of the unburned HC from the turbine agitation to greatly raise the exhaust-gas temperature, for effectively promoting
Fujii Mikihito
Uchida Hiroyasu
Umezono Kazuaki
Denion Thomas
Mazda Motor Corporation
Nguyen Tu M.
Nixon & Peabody LLP
Studebaker Donald R.
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