Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-01-11
2001-06-12
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S399000, C123S406510, C123S486000
Reexamination Certificate
active
06244243
ABSTRACT:
This application is based on patent application No. 11-7233 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
This invention relates to a control device for a direct injection engine in which fuel is injected directly into a combustion chamber in a cylinder by means of a fuel injection valve, and such an injection engine. More particularly, the invention is concerned with a technique of throttle control during acceleration of a direct injection engine which can be switched between uniform charge combustion mode and stratified charge combustion mode.
A known example of a conventional control device for this type of direct injection engine is found in Japanese Unexamined Patent Publication No. 7-301139, in which the engine is operated in stratified charge combustion mode by injecting the fuel into a cylinder during a compression stroke in a specific low-speed, low-load operating range of the engine while it is operated in uniform charge combustion mode by injecting the fuel into the cylinder during an intake stroke in other operating ranges. More specifically, a region of a relatively rich mixture is formed close to a spark plug and a stratiform mixture is formed around the region of the rich mixture in the stratified charge combustion mode. Since the engine is run at an extremely high average air-fuel ratio within a combustion chamber in the stratified charge combustion mode, it is possible to significantly increase the opening of a throttle valve compared to its opening in the uniform charge combustion mode, and this helps decrease pumping loss of the engine and achieve a reduction in fuel cost.
The aforementioned control device for the direct injection engine however has a problem that torque shock occurs when the engine is switched from the stratified charge combustion mode to the uniform charge combustion mode during acceleration, for instance. Since the throttle opening in the stratified charge combustion mode is larger than the throttle opening in the uniform charge combustion mode as stated above, the throttle valve is usually closed for an instant when the combustion mode is switched during engine acceleration. Even if the throttle valve is temporarily closed in this fashion, there occurs a considerable time delay before the charging efficiency in the cylinder actually drops and, therefore, the charging efficiency in the cylinder increases up to an excessive level, thereby increasing engine torque excessively when the engine is switched to the uniform charge combustion mode.
One approach to reducing such variations in engine torque would be to control the throttle valve in such a way that its opening becomes as small as possible in the stratified charge combustion mode. Even when this approach is used, however, the opening of the throttle valve is increased in accordance with an increase in target load level during acceleration of the engine, so that the throttle opening is fairly large immediately before the engine is switched to the uniform charge combustion mode and the aforementioned torque shock inevitably occurs after all at the time of combustion mode switching.
Another approach would be to delay the switching to a fuel injection pattern of the uniform charge combustion mode until the amount of intake air decreases as disclosed in Japanese Unexamined Patent Publication No. 4-36221, or to temporarily close the throttle valve as described above and delay the switching of the fuel injection pattern until the charging efficiency in the cylinder actually decreases, when switching the engine to the uniform charge combustion mode. Even when such an approach is taken, however, there arises a problem that vehicle acceleration performance deteriorates since transition to the uniform charge combustion mode is practically retarded, also causing a delay in increasing the amount of fuel.
Still another approach would be to forcibly decrease the engine torque by retarding ignition timing by a specific time period to alleviate the torque shock when switching the combustion mode. However, this approach makes it necessary to significantly retard the ignition timing so that there arises a problem that fuel economy considerably deteriorates. Furthermore, the reliability of a catalyst for converting exhaust gas might be impaired due to an excessive increase in exhaust gas temperature.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a control device for a direct injection engine and an injection engine which have 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 and an injection engine which can be switched between uniform charge combustion mode and stratified charge combustion mode, the control device employing an innovative throttle valve control sequence which makes it possible to prevent torque shock at combustion mode switching without causing such problems as deterioration in vehicle acceleration performance or in fuel economy.
According to an aspect of the invention, a control device for controlling a direct injection engine predicts a switching from a stratified charge combustion mode to a uniform charge combustion mode, and makes a correction to the opening of a throttle valve so that it becomes approximately equal to a throttle opening suited for the uniform charge combustion mode prior to the switching of the combustion mode.
According to another aspect of the invention, an injection engine comprises: a cylinder having a combustion chamber; a fuel injection valve for injecting fuel directly into the combustion chamber; a spark plug; a throttle valve for regulating the amount of intake air introduced into the combustion chamber; and a controller. The controller switchingly sets a stratified charge combustion mode where the fuel is injected in a compression stroke of the cylinder to produce a stratified mixture around the spark plug and burnt in a stratified state and a uniform charge combustion mode where the fuel is injected in an intake stroke of the cylinder to produce a uniformly distributed mixture therein and burnt in a uniform state, and sets a target load according at least to the amount of depression of an accelerator pedal, and controls the opening of the throttle valve according at least to the set target load, and predicts a switching from the stratified charge combustion mode to the uniform charge combustion mode, and corrects a control target value for the set throttle valve so that the control target value approaches a target value which will become valid in the uniform charge combustion mode prior to the switching to the uniform charge combustion mode when such combustion mode switching has been predicted.
The control device is useable for an engine provided with a fuel injection valve for injecting fuel directly into a combustion chamber in a cylinder thereof, a throttle valve for regulating the amount of intake air introduced into the combustion chamber, and a spark plug.
The control device is provided with a mode setter for switchingly setting a stratified charge combustion mode where the fuel injection valve injects the fuel in a compression stroke of the cylinder to produce a stratified mixture around the spark plug and the mixture is burnt in a stratified state and a uniform charge combustion mode where the fuel injection valve injects the fuel in an intake stroke of the cylinder to produce a uniformly distributed mixture therein and the mixture is burnt in a uniform state, a target load setter a for setting a target load of the engine according at least to the amount of depression of an accelerator pedal, a throttle controller for controlling the opening of the throttle valve according at least to the target load set by the target load setter, a mode change predictor for predicting a switching from the stratified charge combustion mode to the uniform charge combustion mode, and a throttle control corrector for correcting a control target value for the throttle valve set by the throttle
Imada Michihiro
Mamiya Kiyotaka
Tetsuno Masayuki
Argenbright Tony M.
Brooks & Kushman P.C.
Mazda Motor Corporation
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