Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1996-10-04
1998-11-10
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Fuel injection system
123480, F02M 5100
Patent
active
058329013
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to fuel injection control apparatus and method which are suitable for use with an internal combustion engine, particularly suited for an in-cylinder injection type automotive internal combustion engine which is adapted to directly inject fuel into cylinders.
BACKGROUND ART
A multi-point type injection system (hereinafter referred to an MPI) having fuel injection valves (injectors) which are provided for respective cylinders is known as a fuel supply system for internal combustion engines. Generally, an MPI type internal combustion engine is provided with injectors which are arranged to be open to the intake manifold, and operates to inject fuel into the intake manifold through the injectors in the exhaust stroke before the intake stroke.
Ordinarily, as the injector, an electromagnetically-driven injector which is easily electronically controllable is employed. In this case, the intake air amount, supplied during a time period between preset crank phases and indicative of the engine driving state, is repeatedly detected, and a fuel injection amount corresponding to the air amount supplied into each cylinder in one intake stroke is repeatedly derived based on the thus detected intake air amount information. Further, in accordance with the result of this derivation, the injector is driven to supply the fuel.
To drive the injector, it is necessary to set the fuel injection amount and fuel injection time period. Setting of these fuel injection parameters is carried out based on the driving state (for example, detected intake air amount) of the engine. For injectors of a type where the fuel injection amount is determinable according to the valve opening time period (fuel injection time period), the fuel injection amount and fuel injection termination timing are set according to the detected intake air amount. Then, the fuel injection starting timing is set at a time point which is earlier than the fuel injection termination timing by the fuel injection time period corresponding to the fuel injection amount.
In order to drive the injector in the exhaust stroke as described above, ordinarily, based on the intake air amount detected in a desired stroke (e.g., explosion stroke) before the preceding exhaust stroke, an amount of air which will be supplied into the associated cylinder in the intake stroke subsequent to the desired stroke is estimated. Then, the fuel injection amount and fuel injection timing are set such that they correspond to the estimated value.
In an MPI engine of an ordinary type adapted to inject fuel into the intake manifold, the fuel (gasoline) is hard to be atomized and vaporized if a period of time from the fuel injection timing to the intake valve opening timing is short. Therefore, the fuel injection is effected at a certain timing in the exhaust stroke, as described above.
Recently, instead of conventional manifold-injection engines, fuel injection spark-ignition internal combustion engines of an in-cylinder injection type (hereinafter referred to as in-cylinder injection engines or cylinder-injection engines) adapted to directly inject fuel into combustion chambers and mounted on automobiles or the like have been proposed from the view points of reducing noxious exhaust gas and improving the fuel efficiency or the like. In these cylinder-injection engines, fuel is more easily atomized as compared with the case of intake-manifold injection and is generally injected at a high injection pressure towards a portion near the ignition plug or a top portion of the piston.
Specifically, at the time of light load, for example, a relatively small amount of fuel is injected into the portion near the ignition plug in a latter stage of the explosion stroke in which air flow is weak, so that only that portion which is in the vicinity of the ignition plug is set into a state having an air-fuel ratio approximately equal to the stoichiometric air-fuel ratio and the remaining portion is set into an extremely lean air-fuel ratio state, to thereby attain preferable c
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Iida Kazumasa
Miyamoto Katsuhiko
Ueda Katsunori
Yoshida Masato
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
Nelli Raymond A.
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