Internal-combustion engines – Charge forming device – Including means responsive to instantaneous change in engine...
Reexamination Certificate
2004-01-08
2004-10-19
Kwon, John T. (Department: 3747)
Internal-combustion engines
Charge forming device
Including means responsive to instantaneous change in engine...
C123S406240, C123S491000
Reexamination Certificate
active
06805100
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2003-017043 filed on Jan. 27, 2003 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a combustion control apparatus and a combustion control method for an in-cylinder injection internal combustion engine.
2. Description of the Related Art
In an internal combustion engine mounted in an automobile or the like, the temperature of a catalyst is increased by increasing the temperature of exhaust gas in a warming-up process after the engine is started such that the catalyst is activated and necessary exhaust gas purification performance can be obtained early after the engine is started. Japanese Patent Laid-Open Publication No. 10-169488 proposes an in-cylinder injection internal combustion engine in which compression stroke injection is executed in an engine warming-up process from when the engine is started until when an increase in the temperature of a catalyst is completed such that the temperature of exhaust gas is increased, thereby increasing the temperature of the catalyst.
In the case where heavy fuel that has lower volatility than standard fuel is used in the in-cylinder injection internal combustion engine, combustion may deteriorate while the compression stroke injection is executed in the engine warming-up process. When the compression stroke injection is executed, ignition is performed while there is a combustible fuel-air mixture around an ignition plug, whereby combustion is performed. However, in the case where the compression stroke injection is executed in the engine warming-up process, and the heavy fuel having low volatility is used, it is difficult to allow a fuel-air mixture with a fuel concentration necessary for stable combustion to remain around the ignition plug at the time of ignition. Therefore, while the compression stroke injection is executed in the engine warming-up process in the case where the heavy fuel is used, combustion may deteriorate and the engine speed may drop, which may cause a stall or rough idling.
In order to address such problems due to use of the heavy fuel, it is proposed to perform a stabilization control which stabilizes combustion when the engine speed drops in the engine warming-up process. Examples of the stabilization control include a control that increases a fuel injection amount, which is disclosed in Japanese Patent Laid-Open Publication No. 8-4571, and a control that advances ignition timing, which is disclosed in Japanese Patent Laid-Open Publication No. 9-158774.
In the case where the aforementioned control that increases the fuel injection amount is executed, the fuel concentration of the air-fuel mixture around the ignition plug at the time of ignition is increased, whereby deterioration of the combustion due to use of heavy fuel can be suppressed when injection is executed in the engine warming-up process and heavy fuel is used. Also, when the temperature of the catalyst is increased in the engine warming-up process, preference is given to the increase in the temperature of the exhaust gas over realization of stable combustion, and the ignition timing is generally delayed. Since the delay amount of the ignition timing is decreased by the aforementioned control that advances the ignition timing, deterioration of the combustion is suppressed in the case where the compression stroke injection is executed in the engine warming-up process and heavy fuel is used.
Meanwhile, the engine speed may temporarily drop in the case where disturbance such as resistance when a vehicle takes off is applied to the internal combustion engine. The fuel injection amount is increased or the ignition timing is delayed by the stabilization control also based on such a temporary drop of the engine speed due to reason other than unstable combustion. In this case, a controlled variable such as the fuel injection amount or the ignition timing deviates from the optimum value for performing desired operation of the engine, which leads to deterioration of fuel efficiency and exhaust gas emission.
Accordingly, it is preferable that the stabilization control based on the drop of the engine speed should be executed, for example, only during a period from when the engine is started until when the combustion by the compression stroke injection is stabilized in the engine warming-up process, and the stabilization control should be stopped after the combustion is stabilized in the middle of execution of the compression stroke injection. By limiting the execution period of the stabilization control in this manner, an unnecessary increase in the fuel injection amount or unnecessary advance of the ignition timing based on the temporary drop of the engine speed due to disturbance can be suppressed, and therefore, deterioration of fuel efficiency and exhaust gas emission can be suppressed as much as possible.
In the in-cylinder injection internal combustion engine, in the case where the compression stroke injection is executed for increasing the temperature of the catalyst in the engine warming-up process, a fuel injection mode is switched from the compression stroke injection to intake stroke injection when the increase in the temperature of the catalyst is completed. In the case of the intake stroke injection, fuel injected into a combustion chamber is easily diffused in the combustion chamber until ignition. Therefore, the fuel concentration of the air-fuel mixture around the ignition plug at the time of ignition tends to be low in the engine warming-up process. Accordingly, the time required for the fuel concentration to reach a level necessary for obtaining stable combustion is long, as compared with the compression stroke injection.
Thus, in the case where heavy fuel having low volatility is used, when the fuel injection mode is switched from the compression stroke injection to the intake stroke injection after the increase in the temperature of the catalyst is completed as described above, it becomes difficult to allow the air-fuel mixture with a fuel concentration necessary for obtaining stable combustion to remain around the ignition plug at the time of ignition by the intake stroke injection. Thus, the combustion becomes unstable after the intake stroke combustion is started, which causes the engine speed to drop.
However, even if the engine speed drops due to unstable combustion after the intake stroke injection is started, the fuel injection amount cannot be increased and the ignition timing cannot be advanced based on the drop of the engine speed, since the stabilization control for suppressing the unstable combustion is stopped when the combustion is stabilized in the middle of execution of the compression stroke injection. Accordingly, the drop of the engine speed cannot be suppressed, and rough idling is caused due to the drop of the engine speed.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a combustion control apparatus and a combustion control method for an in-cylinder injection internal combustion engine, which do not unnecessarily execute a stabilization control while compression stroke injection is executed after the engine is started, and can appropriately suppress unstable combustion by the stabilization control when a fuel injection mode is switched from the compression stroke injection to intake stroke injection.
A first aspect of the invention relates to a combustion control apparatus for an in-cylinder injection internal combustion engine including a stabilization controller, an execution stop controller, and a restart controller. The stabilization controller executes a stabilization control that stabilizes combustion by changing a controlled variable used for controlling operation of the engine when an engine speed drops in an engine warming-up process after the engine is started, wherein compression stroke injection is executed in the engine warming-up process. The execution stop controller limits an
Kenyon & Kenyon
Kwon John T.
Toyota Jidosha & Kabushiki Kaisha
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