Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2001-09-04
2002-04-16
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S299000, C123S357000
Reexamination Certificate
active
06371086
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-278681 filed on Sep. 8, 2000 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 an apparatus and a method for controlling fuel injection in an internal combustion engine and, more particularly, to a fuel injection control apparatus and a fuel injection control method for an engine having a direct fuel injection valve for injecting fuel directly into a cylinder.
2. Description of the Related Art
A widely known evaporated fuel purge apparatus prevents release of evaporated fuel (fuel vapor) from a fuel tank into the atmosphere by temporarily adsorbing fuel vapor from the tank to a canister containing activated carbon or the like and supplying (purging) fuel vapor adsorbed to the activate carbon into an engine intake passage during operation of the engine so that the fuel vapor bums in the engine.
When the purging of fuel vapor is performed, an excess amount of fuel corresponding to the amount of fuel vapor is supplied into the engine together with intake air. Therefore, if the amount of fuel injected into the engine when the purging is not performed is maintained when the purging is performed, the engine air-fuel ratio changes (decreases), so that the state of combustion in the engine may deteriorate in some cases. Therefore, according to the conventional art, when a purge is executed, the amount of fuel injected into the engine is corrected by subtracting an amount corresponding to the amount of fuel vapor supplied to the engine from the amount supplied when a purge is not executed.
An example of an engine in which the aforementioned type of reducing correction is performed is described in, for example, Japanese Patent Application Laid-Open No. 2000-27716. The engine described in this laid-open patent application is designed as a spark-ignition engine equipped with direct fuel injection valves for injecting fuel directly into the cylinders wherein, during the compression stroke of each cylinder, fuel injection is performed so that a mixture gas layer of a combustible air-fuel ratio is formed only in the vicinity of an ignition plug within the air compressed in the cylinder and containing no fuel.
According to the conventional art, the engine capable of performing the stratified charge combustion has a problem that the aforementioned purge cannot be performed during the stratified charge combustion mode. If a purge were performed to supply air containing fuel vapor into each cylinder during the stratified charge combustion mode and fuel were injected from the fuel injection valve into the fuel vapor-containing air in each cylinder during the compression stroke, the air-fuel ratio of a combustible mixture gas layer formed by the fuel injection would have a dropped air-fuel ratio. Thus, the air-fuel ratio of the combustible mixture gas layer would excessively shift to the fuel-rich side, resulting in degraded combustion. This undesired phenomenon is generally termed disturbed stratified charge combustion.
The aforementioned engine described in Japanese Patent Application Laid-Open No. 2000-27716 is designed so as to mitigate the problem of disturbed stratified charge combustion by forming swirls in each cylinder during the intake stroke and supplying fuel vapor into each cylinder through the use of swirls so that fuel vapor exists only in one of the air layer and the combustible mixture gas layer formed in each cylinder, and by correcting the amount of fuel injected in the reducing direction in accordance with the amount of fuel vapor.
However, despite the design for the localization of fuel vapor in each cylinder and the correction of reducing the amount of fuel injection in accordance with the amount of fuel vapor, the engine of the Japanese Patent Application Laid-Open No. 2000-27716 has a problem of being incapable of completely preventing disturbed stratified charge combustion.
For example, in direct fuel injection type engines, the timing of fuel injection (i.e., the fuel injection starting timing and the fuel injection ending timing) greatly affects the state of formation of a mixture gas. Therefore, the fuel injection timing is set with high precision so as to provide an optimal mixture in accordance with the amount of fuel injection, the engine revolution speed, the load, etc. Hence, if the amount of fuel injection changes, the optimal fuel injection timing changes even though the other states of engine operation, for example, the engine revolution speed, the load etc., remain unchanged. Normally, the amount of fuel injection is changed by changing the open valve duration of the fuel injection valves (injection duration). Therefore, in the engine of the aforementioned patent application as well, the fuel injection timing is changed in response to a change in the amount of fuel injection. However, normally, the fuel injection duration is controlled so that the fuel injection duration is changed by changing one of the valve opening timing of the fuel injection valves (fuel injection starting timing) and the valve closing timing of the fuel injection valves (fuel injection ending timing) while fixing the other timing. Therefore, in the aforementioned apparatus described in Japanese Patent Application Laid-Open No. 2000-27716, the fuel injection starting timing or the fuel injection ending timing is fixed even when the amount of fuel injection is reduced for correction. Thus, there is a problem of being incapable of performing fuel injection that is optimal in view of the amount of fuel injection, the engine operation state, etc.
Although the above-described problem is related to the stratified charge combustion, similar problems also occur in conjunction with an engine operation in which fuel is injected into each cylinder during the intake stroke to form a homogeneous mixture gas in the cylinder (homogeneous mixture combustion), and an engine operation in which fuel injection is performed in a divided manner during the intake stroke and during the compression stroke, and in which fuel injected during the compression stroke is stratified in a homogeneous lean mixture formed by the fuel injected during the intake stroke so that the fuel injected during the compression stroke forms a combustible mixture layer around a spark plug in each cylinder (weak stratified charge combustion). That is, similar problems occur if only one of the fuel injection starting timing and the fuel injection ending timing is changed in accordance with a change in the amount of fuel injection.
More specifically, in direct fuel injection type spark injection engines, the problem of failing to accomplish optimal combustion occurs during not only the stratified charge combustion operation but also the homogeneous mixture combustion operation and the weak stratified charge combustion operation if only the amount of fuel injection is corrected at the time of execution of a purge.
With regard to correction of the amount of fuel injection in accordance with the amount of fuel vapor as well, it is a normal practice to, during the weak stratified charge combustion operation, correct (i.e. reduce) the amount of fuel injected by the intake stroke fuel injection and the amount of fuel injected by the compression stroke fuel injection at equal rates in accordance with the amount of fuel vapor. However, since the formation of a mixture of fuel injected during the intake stroke and the formation of a mixture of fuel injected during the compression stroke are completely different, optimal mixtures cannot be formed in each cylinder if the two amounts of fuel injection are merely reduced at equal rates at the time of execution of a purge. In some cases, therefore, combustion may deteriorate.
SUMMARY OF THE INVENTION
It is an object of the invention to provide fuel injection control apparatus and method capable of controlling fuel injection so as to achieve an optimal state of combustion in accordance with op
Matsubara Takuji
Yoshioka Mamoru
Miller Carl S.
Toyota Jidosha & Kabushiki Kaisha
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