Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2003-04-17
2004-05-25
Mohanty, Bibhu (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S520000
Reexamination Certificate
active
06739320
ABSTRACT:
The disclosure of Japanese Patent Application No. 2002-163576 filed on Apr. 26, 2002, including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an evaporative fuel processing system for an in-cylinder fuel injection type internal combustion engine, in which an evaporative fuel processing mechanism is provided for purging the evaporative fuel in a fuel supply system to an intake system and an evaporative fuel processing method. More specifically, the invention relates to an evaporative fuel processing system and method for controlling a flow rate of the evaporative fuel to be purged to the intake system by the evaporative fuel processing mechanism in accordance with an air/fuel ratio of the internal combustion engine.
2. Description of Related Art
Generally in an internal combustion engine, an evaporative fuel generated in a fuel supply system such as a fuel tank is temporarily adsorbed in a canister. The adsorbed evaporative fuel is introduced as purge gas to the intake system at a predeternined timing so as to be treated or purged. As the purge gas has a high fuel content, the air/fuel ratio may fluctuate if the quantity of the purge gas is not appropriately controlled.
In JP-A 2001-152931, a variance tendency of an actual air/fuel ratio with respect to a target air/fuel ratio, which is obtained by an air/fuel ratio feedback control is monitored so as to learn the fuel concentration of the purge gas (purge concentration) on the basis of the monitored variance tendency. The flow rate of the purge gas is controlled in accordance with the purge concentration such that appropriate quantity of the purge gas in accordance with the operating state of the engine is introduced into the intake system.
The internal combustion engine is provided with a crankcase emission control system for treating gas that leaks out of the cylinder to the crankcase, that is, blowby gas having strong acidity that may cause rust on a metal part of the engine body or deteriorate the lubricating oil therein. The crankcase emission control system introduces new air from outside (through air cleaner provided in the intake system) into the engine body, and circulates the introduced air within the crankcase so as to be returned to the intake system. Implementing the aforementioned scavenging process makes it possible to treat the blowby gas without being discharged to the outside.
Returning the blowby gas containing uncombusted fuel to the intake system may substantially fluctuate the fuel injection quantity. Normally, however, the uncombusted fuel concentration of the blowby gas is not so high nor largely fluctuates. Therefore, an air/fuel ratio feedback control is performed to cope with the fluctuation of the fuel injection quantity so as to restrain the adverse effect resulting from such fluctuation.
Unlike the internal combustion engine using the intake port, in the in-cylinder fuel injection type internal combustion engine where the fuel is directly injected into the cylinder from the fuel injection valve, the distance between the nozzle hole of the fuel injection valve and the inner peripheral surface of the cylinder is so short that the injected fuel directly impinges on the inner peripheral surface. The aforementioned type of the internal combustion engine may cause problems as described below.
In the above type of the internal combustion engine in the cold state, it is difficult to promote atomization of the fuel in the cylinder, and as a result, the injected fuel is partially kept uncombusted and adhered to the inner peripheral surface of the cylinder. The adhered fuel is mixed with the lubricating oil applied on the inner peripheral surface of the cylinder for lubrication. Accordingly, the lubricating oil is diluted with the fuel.
The lubricating oil that has been diluted with the fuel is peeled off from the inner peripheral surface of the cylinder as the piston reciprocates, and returned to a crankcase (more particularly, an oil pan formed in the crankcase) so as to be used for lubricating the piston and the like in the internal combustion engine. If the aforementioned dilution of the lubricating oil frequently occurs, the quantity of the fuel to be mixed with the lubricating oil in the crankcase, that is, the whole lubricating oil supplied for lubricating the internal combustion engine may gradually increase.
As the fuel content in the lubricating oil increases, a large quantity of the fuel evaporates from the lubricating oil. This may considerably raise the fuel concentration in the blowby gas. If the aforementioned blowby gas with increased fuel concentration is introduced in the intake system, the variance tendency of the actual air/fuel ratio with respect to the target air/fuel ratio largely fluctuates. If the purge concentration is learned in the aforementioned case, however, it may be mistakenly determined that the fluctuation of the air/fuel ratio variance tendency has been caused by the change in the purge concentration.
The adverse effect resulting from the aforementioned error in learning of the purge concentration is more likely to occur in the engine operation at low load where the flow rate of the purge gas is set to a small value. Therefore, if the engine operation is rapidly brought into the transient stage from the low load where it is likely to be adversely affected by the error in the learning to the high load where it is less likely to be adversely affected by the error, the purge concentration varies as if it were caused by the change in the load state. As a result, fluctuation of the air/fuel ratio during such transient operation of the engine inevitably occurs.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an evaporative fuel processing system for an in-cylinder fuel injection type internal combustion engine to restrain fluctuation of the air/fuel ratio of the engine at the transient operation stage, which is caused by an adverse influence of dilution of the lubricating oil with fuel to purging control, especially, the error in learning of the purge concentration.
According to an embodiment of the invention, an evaporative fuel processing system for an in-cylinder injection type internal combustion engine includes an evaporative fuel processing mechanism that includes a canister to which an evaporative fuel in a fuel supply system is adsorbed and performs an operation for purging the adsorbed evaporative fuel into an intake system of the internal combustion engine. The system further includes a controller that estimates a degree of dilution occurred in a lubricating oil for the internal combustion engine with a fuel mixed therewith, and inhibits the purging operation performed by the evaporative fuel processing mechanism when the estimated degree of dilution is equal to or larger than a predetermined value.
In the aforementioned embodiment, the degree of dilution of the lubricating oil with the fuel is estimated. The purging performed by the evaporative fuel processing mechanism is inhibited if the estimated degree of dilution is higher than a predetermined level. This makes it possible to prevent the error in learning of purge concentration even if the fuel evaporating from the lubricating oil is introduced into the intake system. This may restrain fluctuation of the air/fuel ratio of the engine at the transient operation stage, which is caused by the adverse influence of the dilution of the lubricating oil with the fuel to the purge control, especially, the error in learning of the purge concentration.
In the case where quantity of the evaporative fuel from the lubricating oil is increasing, it is likely that the actual air/fuel ratio shows a variance tendency from the target air/fuel ratio to the fuel rich side. Meanwhile, it is unlikely that the actual air/fuel ratio shows a variance tendency from the target air/fuel ratio to the fuel lean state. Even if an air/fuel ratio correction amount derived from the aforementioned variance
Hirose Kiyoo
Honda Koji
Ito Yukikazu
LandOfFree
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