Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-06-05
2001-11-06
Solis, Erick (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S090150
Reexamination Certificate
active
06311667
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control apparatus for internal combustion engines that includes a variable valve timing mechanism for adjusting the valve overlap of intake valves and exhaust valves and changes the combustion mode between stratified combustion and homogeneous combustion.
Japanese Unexamined Patent Publication No. 5-248277 discloses a combustion control apparatus that has fuel injectors located in combustion chambers of an engine. The apparatus changes the combustion mode of the engine between stratified combustion and homogeneous combustion according to the current running state of the engine. Specifically, when the engine is running with a relatively small load, the apparatus performs stratified combustion by injecting fuel in the vicinity of the spark plug in each combustion chamber at the end of the compression stroke. At this time, the fuel is concentrated about the spark plug. When the engine load is relatively high, the apparatus performs homogeneous charge combustion by homogeneously injecting fuel into each entire combustion chamber during the intake stroke.
The apparatus of the publication No. 5-248277 also includes a variable valve timing mechanism to adjust the valve overlap in accordance with the state of air-fuel mixture during the stratified and homogenous combustion modes. Particularly, during stratified combustion, the valve overlap is adjusted to create inner exhaust gas recirculation (EGR), which improves combustion and reduces NO
x
in the emission.
As described above, the apparatus of the publication optimizes the combustion state of the engine by adjusting the valve overlap in accordance with the current combustion mode referring to the current running state of the engine. However, this apparatus sometimes fails to control the valve overlap in accordance with the engine running state.
For example, the apparatus cannot control the valve overlap when the variable valve timing mechanism is not operating normally, that is, when the mechanism is malfunctioning or when the power supplied to the mechanism is insufficient. Also, the apparatus cannot control the valve overlap when the variable valve timing mechanism is not operating in accordance with the running state of the engine, that is, when a procedure for determining a referential position of the mechanism has not been executed.
In these cases, stratified combustion hinders the internal EGR control, which deteriorates the combustion of the engine. A reduced amount of EGR increases the amount of NO
x
in the emissions.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a combustion control apparatus for an internal combustion engine that improves the combustion state of the engine and reduces the NO
x
in the emission even if the valve overlap is not being controlled in accordance with the running state of the engine.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an apparatus for controlling an engine is provided. The engine has a variable valve timing mechanism to adjust the valve overlap of an intake valve and an exhaust valve in accordance with the running state of the engine. The engine operates in a combustion mode selected from a plurality of combustion modes in accordance with the running state of the engine. The combustion modes include a stratified charge combustion mode, in which a mixture of air and fuel is non-uniformly injected into a combustion chamber, and a homogeneous charge combustion mode, in which the mixture is distributed in a homogeneous manner in the combustion chamber. The apparatus includes a controller and means for determining whether the state of the variable valve timing mechanism is suitable for stratified charge combustion. When the state of the variable valve timing mechanism is judged to be not suitable for stratified charge combustion, the controller forces the engine to perform homogeneous charge combustion regardless of the running state of the engine.
The present invention may also be embodied in a method for controlling an engine. The method includes adjusting the valve overlap of an intake valve and an exhaust valve with a variable valve timing mechanism in accordance with the running state of the engine, and selecting a combustion mode from various combustion modes in accordance with the running state of the engine. The combustion modes include a stratified charge combustion mode, in which a mixture of air and fuel is non-uniformly injected into a combustion chamber, and a homogeneous charge combustion mode, in which the mixture is distributed in a homogeneous manner in the combustion chamber. The method further includes determining whether the state of the variable valve timing mechanism is suitable for stratified charge combustion. When the state of the variable valve timing mechanism is judged to be not suitable for stratified charge combustion, homogeneous charge combustion mode is selected regardless of the running state of the engine.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
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patent: 5927238 (1999-07-01), Watson
patent: 5967114 (1999-10-01), Yasuoka
patent: 6006725 (1999-12-01), Stefanopolou et al.
patent: 6055948 (2000-05-01), Shiraishi et al.
patent: 6148791 (2000-11-01), Fujieda et al.
patent: 6196183 (2001-03-01), Bauer et al.
patent: 6250283 (2001-06-01), Russell et al.
patent: 5248277A (1993-09-01), None
patent: 9280092A (1997-10-01), None
Kamijyo Yusuke
Kato Senji
Satou Fumikazu
Kenyon & Kenyon
Solis Erick
Toyota Jidosha & Kabushiki Kaisha
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