Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
1999-08-03
2001-06-05
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...
C060S285000, C060S286000, C123S478000
Reexamination Certificate
active
06240724
ABSTRACT:
This application is based on patent application No. 10-223436 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
This invention relates to control of fuel injection during a period when a catalytic converter is not heated yet in a direct injection engine provided with an injector which injects fuel directly into a combustion chamber.
The type of direct injection engine having a fuel injector which injects fuel directly into the combustion chamber is known in the prior art. Unlike other conventional arrangement in which an injector is provided in an intake passage, the direct injection engine does not cause a problem of fuel condensation on passage walls. Therefore, it provides excellent stability and response characteristics with respect to air-fuel ratio control. In addition, if the combustion chamber is designed in such a shape that an air-fuel mixture is locally distributed around a spark plug when the fuel is injected in the latter half of each compression stroke, it is possible to make the mixture leaner (higher air-fuel ratio) as a whole by using so-called stratified charge technology and thereby achieve an improvement in fuel economy.
Exhaust gases from automotive engines, for instance, contain hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). There is a demand today to reduce generation and release of these harmful constituents as much as possible to obtain improved properties of automotive emissions. One approach that has conventionally been practiced is to provide a catalyst in an exhaust passage, as is widely done in the direct injection engine.
However, catalysts used for converting the exhaust gases can not fully exhibit their conversion effects in a cold-start condition when the catalysts are at a temperature lower than their activation temperature and, therefore, considerable quantities of HC and NOx constituents are likely to be released if it takes a long time for the catalysts to reach the activation temperature.
A device intended to provide means for overcoming this problem is disclosed in U.S. Pat. No. 5,655,365, for example. This device delays the ignition timing of at least one cylinder to a point beyond its top dead center and increases the ratio of fuel to a higher level than required when the engine is in its normal operating condition while a catalyst is not heated yet. As a result, the exhaust gas temperature is increased, so that heating of the catalyst is promoted. When applied to a direct injection engine, the device injects a specified amount of fuel completely during a particular period before the top dead center (e.g., 60° to 80° before the top dead center, hereinafter referred to as BTDC) in each compression stroke.
The device disclosed in the Patent Publication promotes quick light-off mainly by retarding the ignition timing while supplying an excess amount of fuel during the period when the catalyst is not heated yet, and in controlling fuel injection from an injector in the direct injection engine, the device injects the fuel only in each compression stroke. If fuel injection is controlled in this manner, however, the fuel economy significantly deteriorates when engine load increases and the amount of injected fuel increases, for example, although sufficient effects are not obtained with respect to the reduction in HC and NOx emissions and increase in the exhaust gas temperature. Thus, there is left room for improvements in this device.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a control device for a direct injection engine which has overcome the problems residing in the prior art.
It is another object of the invention to provide a control device for a direct injection engine which can improve the properties of emissions by cutting down HC and NOx contents while reducing deterioration in fuel economy to a relatively low level from low-load to high-load engine states and can increase quick light-off effect due to an increase in exhaust gas temperature.
According to an aspect of the invention, a control device for a direct injection engine having a catalyst provided in an exhaust passage for converting exhaust gases and an injector for injecting fuel directly into a combustion chamber comprises a temperature state identifier for judging the temperature state of the catalyst, a load condition detector for sensing engine load conditions, and a fuel injection controller for controlling fuel injection from the injector. The fuel injection controller performs quick light-off control operation by causing the injector to inject fuel in one-time injection mode during a compression stroke in a specific low-load operating range of the engine when the catalyst is in its unheated state where its temperature is below its activation temperature, and switching the mode of fuel injection to intake-compression stroke split injection mode which includes earlier injection made during an intake stroke and later injection made during the compression stroke in a specific high-load operating range of the engine, based on judgment results of the temperature state identifier and sensing results of the load condition detector.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.
REFERENCES:
patent: 5170759 (1992-12-01), Ito
patent: 5313920 (1994-05-01), Matsushita et al.
patent: 5655365 (1997-08-01), Worth et al.
patent: 5832901 (1998-11-01), Yoshida et al.
patent: 6032637 (2000-03-01), Mamiya et al.
patent: 6062201 (2000-05-01), Nozowa et al.
patent: 404292543A (1992-10-01), None
Fujii Mikihito
Kudou Hidetoshi
Matsumoto Masakazu
Saito Fumihiko
Yamashita Hiroyuki
Denion Thomas
Mazda Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
Trieu Thai-Ba
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