Internal-combustion engines – Charge forming device – Including means responsive to instantaneous change in engine...
Reexamination Certificate
2000-06-02
2002-10-29
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Including means responsive to instantaneous change in engine...
C123S704000, C701S103000, C701S110000
Reexamination Certificate
active
06470854
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No. 11-205759 filed on Jul. 21, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air-fuel ratio control for engines which improves air-fuel mixture supply immediately after completion of mixture combustion for engine starting.
2. Related Art
Conventional engine control systems have a catalytic converter in an exhaust pipe to purify exhaust emissions, and feedback-controls an air-fuel ratio of air-fuel mixture to a stoichiometric ratio in response to the air-fuel ratio detected by an air-fuel ratio sensor. The feedback control is disabled until engine temperature sufficiently rises as disclosed in JP-A-60-3440, because the air-fuel ratio sensor is not operative under low temperatures. Therefore, the feedback control is disabled during an engine starting (cranking by a starter motor) period and a post-starting period.
Further, immediately after the complete combustion of air-fuel mixture in those starting and post-starting periods, the engine rotation speed quickly rises and then falls, thus presenting irregular rotation speed changes. If less-volatile heavy fuel is supplied to the engine, the fuel is likely to remain sticking to intake port walls of the engine during low temperature conditions, thus leaning the air-fuel mixture supplied to the engine. The engine may misfire and stall immediately after engine starting.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an air-fuel ratio control for engines which controls an air-fuel mixture ratio appropriately immediately after a complete mixture combustion in an engine starting operation.
According to the present invention, a target operation characteristics of engine speed is set based on a coolant temperature at the time of starting an engine cranking. The target engine speed is variable with time after starting engine cranking. Immediately after a complete combustion of air-fuel mixture supplied to the engine is detected, an actual engine speed is compared with a target engine speed corresponding to the target operation characteristics, and an air-fuel ratio of mixture supplied to the engine is controlled based on a comparison result. Thus, the air-fuel ratio control is effected immediately after the complete combustion of air-fuel mixture, even when an air-fuel ratio sensor is inoperative to effect an air-fuel ratio feedback control.
Preferably, the target engine speed is determined to converge to a speed value lower than a normal target idle speed, and the air-fuel ratio control based on the comparison result prevails an engine idle speed feedback control. The air-fuel ratio control is effected by using a first correction value calculated as a function of a difference between the target speed and the actual speed, and a second correction value calculated as a function of a difference between the target speed and an estimated future speed estimated from air flow amount. The air-fuel ratio control is further effected by using a combustion unstableness value.
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Asama Hidehiko
Hirata Yasuo
Argenbright Tony M.
Denso Corporation
Huynh Hai
Nixon & Vanderhye P.C.
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