Engine control apparatus

Abstract

Provided is an engine control apparatus equipped with a three-way catalyst for purifying exhaust gas, a unit for calculating an operational state based on outputs from various sensors, a unit for calculating a fuel injection amount, a unit for driving an injector, a unit for calculating an actual misfire ratio, a catalyst damage determining misfire ratio calculating unit for calculating a misfire determining ratio, a catalyst damaging misfire determining unit for cutting off a supply of fuel when it is determined that a damage-causing misfire state has arisen, a unit for storing an actual misfire ratio at a time when it is determined that the damage-causing misfire state has arisen, and a unit for making a recovery from the cutoff of the fuel supply when the misfire determining ratio has become larger than the misfire ratio at the time of the determination that the damage-causing misfire state has arisen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic diagram showing an entire system including an engine control apparatus according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing an ECU of the engine control apparatus according to the first embodiment of the present invention;

FIG. 3 is an explanatory diagram showing a relationship between an operational state of an engine and a misfire determining ratio according to the first embodiment of the present invention;

FIG. 4 is a flowchart showing the operation of the engine control apparatus according to the first embodiment of the present invention;

FIG. 5 is a timing chart for giving a supplementary explanation of the operation of the engine control apparatus according to the first embodiment of the present invention;

FIG. 6 is a timing chart showing the operation of an engine control apparatus according to a second embodiment of the present invention at a time when a change in operational state of an engine has occurred in the neighborhood of a border corresponding to a switchover in misfire determining ratio;

FIG. 7 is a block diagram showing an ECU of the engine control apparatus according to the second embodiment of the present invention;

FIG. 8 is a flowchart showing the operation of the engine control apparatus according to the second embodiment of the present invention;

FIG. 9 is a timing chart showing the operation of an engine control apparatus according to a third embodiment of the present invention at a time when a recovery from the cutoff of the fuel supply is made in a high rotational speed/high load state;

FIG. 10 is a block diagram showing an ECU of the engine control apparatus according to the third embodiment of the present invention;

FIG. 11 is a flowchart showing the operation of the engine control apparatus according to the third embodiment of the present invention;

FIG. 12 is a timing chart showing the operation of an engine control apparatus according to a fourth embodiment of the present invention at a time when a rise in temperature of an engine has been unlikely to occur;

FIG. 13 is a block diagram showing an ECU of the engine control apparatus according to the fourth embodiment of the present invention; and

FIG. 14 is a flowchart showing the operation of the engine control apparatus according to the fourth embodiment of the present invention.

Claims

1. An engine control apparatus comprising: a catalyst provided in an exhaust system of an engine, for purifying exhaust gas;various sensors provided in the engine;an operational state calculating means for calculating an operational state including at least an engine rotational speed and a filling efficiency based on outputs from the sensors;a fuel injection amount calculating means for calculating a fuel injection amount of the engine based on the operational state;an injector driving means for driving an injector for injecting fuel into an arbitrary one of cylinders in accordance with the fuel injection amount;an actual misfire ratio calculating means for making a determination on presence/absence of a misfire and calculating an actual misfire ratio based on the outputs from the sensors;a catalyst damage determining misfire ratio calculating means for calculating a misfire determining ratio for making a determination on a damage-causing misfire state in which the catalyst is assumed to be damaged, based on the operational state;a catalyst damaging misfire determining means for comparing the actual misfire ratio with the misfire determining ratio and cutting off a supply of fuel to a misfired one of the cylinders when it is determined that the damage-causing misfire state has arisen;a misfire ratio storing means for storing the actual misfire ratio at a time when it is determined that the damage-causing misfire state has arisen as a misfire ratio at a time of a determination that the damage-causing misfire state has arisen; anda fuel supply cutoff recovery means for outputting a drive permitting signal to the injector driving means to make a recovery from cutoff of a fuel supply when a predetermined condition is satisfied, whereinthe fuel supply cutoff recovery means determines that the predetermined condition is satisfied when the misfire determining ratio has become larger than the misfire ratio at the time of the determination that the damage-causing misfire state has arisen.

2. An engine control apparatus according to claim 1, further comprising a misfire determining ratio correcting means for subtracting a predetermined misfire ratio from the misfire determining ratio.

3. An engine control apparatus according to claim 1, further comprising a catalyst temperature estimating means for estimating a temperature of the catalyst during normal combustion as an estimated catalyst temperature, wherein the sensors include an intake air amount measuring means for measuring an intake air amount of the engine,the catalyst temperature estimating means estimates the temperature of the catalyst during normal combustion as the estimated catalyst temperature based on outputs from the intake air amount measuring means and the fuel injection amount calculating means, andthe fuel supply cutoff recovery means makes the recovery from the cutoff of the fuel supply when the estimated catalyst temperature is lower than a predetermined catalyst temperature.

4. An engine control apparatus according to claim 1, further comprising: a coolant temperature storing means for storing a coolant temperature at a time when it is determined that the damage-causing misfire state has arisen as a coolant temperature at a time of a determination that the damage-causing misfire state has arisen; anda coolant temperature change calculating means for calculating a change in coolant temperature from the coolant temperature at the time of the determination that the damage-causing misfire state has arisen, whereinthe sensors include a coolant temperature measuring means for measuring a coolant temperature of the engine, andthe fuel supply cutoff recovery means makes the recovery from the cutoff of the fuel supply when the rise in coolant temperature from the coolant temperature at the time of the determination that the damage-causing misfire state has arisen has become equal to or higher than a predetermined coolant temperature in a case where the coolant temperature at the time of the determination that the damage-causing misfire state has arisen is lower than a predetermined lower-limit coolant temperature.