JPH09273415A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the warming up of the catalyst without losing the stability of combustion by switching air-fuel mixture ratio between rich and lean per each predetermined cycle during the time till the catalyst is concluded, and dividing the fuel of the rich combustion to a part to be given for combustion and a part to be given for non-combustion for supply. SOLUTION: A judgment whether an internal combustion engine is rotating at an engine speed or not is performed (S1), in the case of rotating, a judgment whether the condition for rich or lean combustion is satisfied or not is performed per each cylinder (S2). In the case where the condition is satisfied, air-fuel ratio feedback control is stopped, and fuel injection variable of the rich cylinder to be given for combustion and to be given for non-combustion is set (S3). Fuel is jet to the lean cylinder on the basis of the fuel injection variable of the lean cylinder, which is previously set so as to supply oxygen enough for oxidation of the oxide to be discharged from the rich cylinder at the set fuel injection variable (S4). Ignition of the rich cylinder is performed at the same time with the ignition time, which is simultaneously set with the fuel injection variable of the rich cylinder and of which delay angle is corrected, and the torque to be generated by the rich cylinder is controlled at the torque to be generated by the lean cylinder (S5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine for warming up a catalyst for purifying exhaust gas earlier.

[0002]

2. Description of the Related Art As a conventional fuel supply control device for an internal combustion engine, there is, for example, one disclosed in Japanese Patent Application Laid-Open No. 4-308311. This is located in the exhaust pipe of the engine,
A catalyst for purifying exhaust gas, a warm-up state detecting means for detecting a warm-up state of this catalyst, an operating state detecting means for detecting an operating state of the engine, and a required injection amount calculated based on the operating state. A required injection amount calculation means, a required ignition timing calculation means for calculating a required ignition timing, and a correction for correcting the required injection amount so as to oscillate at predetermined time intervals when the catalyst has not been warmed up. Means and an intermittent retard correction means for intermittently retarding the required ignition timing, the engine repeats rich combustion and lean combustion in a state where warm-up of the catalyst is not completed, and occurs during rich combustion The oxidation reaction heat from carbon monoxide and oxygen generated during lean combustion warms the catalyst early, and when the engine torque increases during rich combustion, the ignition timing during rich combustion Reducing the torque by retarding, and suppresses torque fluctuations by reducing the step between the generated torque at the time of lean combustion.

[0003]

However, in such a fuel supply control device for an internal combustion engine, as shown in FIG. 6, carbon monoxide (CO), which is an oxidation target, is generated by rich combustion. Therefore, if an attempt is made to increase the amount of the oxidation target in order to accelerate the warm-up of the catalyst, combustion will become richer, and as a result, more torque will be produced.

Therefore, the torque generated in all cylinders is made equal,
In order to suppress engine vibration and ensure stability, it is required to significantly retard the ignition timing of the rich combustion cylinder.

On the other hand, however, when the ignition timing is greatly retarded, the ignition timing is largely deviated from the required ignition timing for normal combustion, and the combustion in that cylinder becomes unstable, making it difficult to suppress engine vibration and ensure stability. was there.

The present invention has been made by paying attention to such a conventional problem, and increases the oxidation object (CO, HC) while suppressing the enrichment of the air-fuel ratio which is substantially involved in combustion. Accordingly, it is an object of the present invention to provide a fuel supply control device for an internal combustion engine, which can easily suppress vibration of the engine and ensure stability.

[0007]

In order to achieve the above object, the present invention provides a catalyst warm-up state detecting means for detecting a warm-up state of a catalyst provided in an exhaust pipe of an internal combustion engine, and an operating state of the internal combustion engine. Detecting means, a fuel amount calculating means for calculating the fuel amount according to the operating state of the internal combustion engine, an ignition timing calculating means for calculating the ignition timing according to the operating state, and until the catalyst warm-up is completed. In the meantime, fuel supply setting means for correcting the fuel amount and switching the air-fuel ratio between rich and lean at predetermined intervals,
Fuel dividing means for dividing the fuel supply amount set to rich into a combustion donating portion and an unburned donating portion; an injection timing setting means for setting an injection timing of the unburned donating portion after injection of the combustion donating portion;
It is characterized by comprising fuel supply means for supplying fuel to each cylinder based on the set injection timing, and ignition timing correction means for retarding the ignition timing of the cylinder set to rich.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention. First, the structure will be described. Air is sucked into an internal combustion engine 1 mounted on a vehicle from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. At each branch portion of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder. This fuel injection valve 6
Is an electromagnetic fuel injection valve that energizes a solenoid to open the valve and deenergizes to close the valve. The solenoid is energized by a drive pulse signal from a control unit 12 described later to open the valve and is pressure-fed from the fuel pump to supply a pressure regulator. The fuel whose pressure is controlled to a predetermined pressure is injected and supplied to the internal combustion engine 1. Each combustion chamber of the internal combustion engine 1 is provided with a spark plug 7, which causes spark ignition to ignite and burn the air-fuel mixture. Exhaust gas is exhausted from the internal combustion engine 1 to the atmosphere via the exhaust manifold 8, the exhaust duct 9, and the three-way catalyst 10 as an exhaust purification catalyst. The temperature of the three-way catalyst 10 is detected by the catalyst temperature sensor 19.

The control unit 12 includes a CPU and R
A microcomputer including an OM, a RAM, an A / D converter, an input / output interface, etc.,
The operation of the fuel injection valve 6 is controlled by receiving input signals from various sensors and performing arithmetic processing as described later. As the various sensors, an air flow meter 13 is provided in the intake duct 3 and outputs a signal according to the intake air amount of the internal combustion engine 1. A distributor (not shown) has a built-in crank angle sensor 14. The crank unit angle signal output from the crank angle sensor 14 in synchronization with the engine rotation is counted for a certain period of time, or the crank reference angle signal is output. The engine speed N is detected by measuring the cycle. Further, an oxygen sensor 15 as an air-fuel ratio sensor is provided at the collecting portion of the exhaust manifold 8. The temperature of the cooling water flowing through the water jacket is detected by the water temperature sensor 16. The opening of the throttle valve 4 is detected by the throttle opening sensor 17, and the idle state of the engine is detected by the idle switch 18.

Next, the operation of the first embodiment will be described. Air flow meter 13, crank angle sensor 14,
Based on the signals from the water temperature sensor 16, the throttle sensor 17, the idle switch 18, the oxygen sensor 15, and the catalyst temperature sensor 19, the control unit 12 determines the operating state of the internal combustion engine and the catalyst warm-up state. When it is determined that the condition for promoting catalyst warm-up is satisfied, the air-fuel ratio is switched between rich and lean for each cylinder. At this time, the fuel injection amount of the rich cylinder is divided into a combustion-provided portion and an unburned-provided portion, and the fuel is injected from the fuel injection valve 6 according to this division. Then, the ignition timing of the rich cylinder is retarded, and ignition is performed by the spark plug 7.

Details will be described with reference to the flowchart shown in FIG.

First, in step 1 (hereinafter abbreviated as S1), it is determined whether or not the internal combustion engine 1 is rotating based on the engine rotation speed based on a signal from the crank angle sensor 14.
If it is rotating, the process proceeds to S2, and if it is stopped, the flow exits and ends. In S2, it is determined whether or not the conditions for performing rich / lean combustion control for each cylinder are satisfied. If it is a condition to be performed, the process proceeds to S3. The conditions to be performed are the catalyst temperature sensor 1
The catalyst temperature detected by 9 is equal to or lower than a preset temperature, the engine speed detected by the crank angle sensor 14 is within a preset range, and the air flow meter 1
3, the charging efficiency (K * intake air amount / rotational speed: K is a coefficient) of the internal combustion engine 1 calculated from the engine intake air amount detected by 3 and the engine rotation speed detected by the crank angle sensor 14 is preset. In this case, the water temperature detected by the water temperature sensor 16 is equal to or higher than a preset temperature.

In step S3, the air-fuel ratio feedback control using the oxygen sensor 15 is stopped, and the fuel injection amount for the combustion donation of the rich cylinder and the fuel injection amount for the unburned fuel are set.

As the fuel injection amount for combustion supply, the same value as that when rich or lean combustion control is not performed for each cylinder is used. The fuel injection amount of the unburned portion is, for example, at a point A shown in FIG. 5, with a certain margin with respect to the combustion stability limit of the rich cylinder, and the rich cylinder generated torque can be the same as the lean cylinder generated torque. The limit is set in advance and set to that value.

In S4, in order to supply oxygen (O ₂ ) sufficient to oxidize the oxidation target (HC, CO) discharged from the rich cylinder with the fuel injection amount set in S3, for example, B shown in FIG. Fuel is injected into the lean cylinders according to the fuel injection amount of the lean cylinders set in advance as indicated by dots.

At S5, the ignition timing of the rich cylinder is ignited at the ignition timing corrected with the retard angle set in advance at the same time as the fuel injection amount of the rich cylinder at S3, for example, at point A in FIG. Then, the torque generated by the rich cylinder is matched with the torque generated by the lean cylinder. Although not shown, it is possible to separately provide a torque fluctuation detecting means of the engine and feed back the ignition timing of the rich cylinder based on the information so that the generated torques of the rich cylinder and the lean cylinder are matched. Needless to say.

As shown in FIG. 3, the fuel injection into the rich cylinder in S3 is divided into two, and the injection amount before the increase correction of the fuel for the enrichment is injected at the same timing as before the correction, and the unburned portion is supplied. Fuel is injected during the overlap period of the intake valve and the exhaust valve.

The fuel injected during the overlap period is
Through the intake manifold 5 and the intake port, the intake valve portion that is open enters the combustion chamber, and most of it simultaneously escapes from the exhaust valve that is open to the exhaust manifold 8. That is, most of the fuel injected during the overlap period does not contribute to combustion and is discharged to the exhaust manifold 8 as an oxidation object that undergoes an oxidation reaction in the exhaust manifold 8 and the three-way catalyst 10.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, as compared with FIG. 3 of the first embodiment, the timing of injecting the fuel for the unburned portion for enriching the rich cylinder is changed and set just before the intake valve is closed. It was done.

This is particularly effective when there is no overlap between the intake valve and the exhaust valve, or when the period is short.

That is, the fuel injected just before the intake valve is closed adheres to the combustion chamber, and in particular, most of the fuel that has entered the narrow gap between the piston and the cylinder block does not contribute to the combustion, but most of the fuel does not contribute to combustion. 8 is discharged. This is because if fuel is injected before the intake valve opens, the heat from the intake port and intake valve vaporizes the fuel, and most of it contributes to combustion. It occurs because the fuel is not supplied to the combustion chamber. Conventionally, there is one that injects an increased amount at the time of acceleration just before the intake valve is closed. However, in this rich and lean combustion control for each cylinder, warming up of the three-way catalyst 10 is not completed,
That is, the warm-up of the internal combustion engine 1 has not been completed, or
This is performed in a state where the load is low and the exhaust temperature is low. In that state, as described above, most of the injected fuel can be discharged to the exhaust manifold 8.

As described above, according to the above-described embodiment, the fuel injection of the rich cylinder is divided into two, the fuel for the combustion supply is injected, and the fuel as the unburned supply is used for the intake valve. Exhaust valve overlap period, or
By injecting just before the intake valve is closed, the unburned portion of the fuel is discharged to the exhaust manifold with almost no contribution to combustion, and even if the supply air-fuel ratio is rich, the actual combustion air-fuel ratio is almost the theoretical air-fuel ratio (λ = 1) It can be controlled to the vicinity, and the oxidation target (HC) can be increased without significantly increasing the generated torque of the rich cylinder with respect to the generated torque of the lean cylinder.
In other words, it is possible to reduce the delay margin of the ignition timing of the rich cylinder,
In order to accelerate the warm-up of the catalyst, even if the oxidation target (HC) is further increased, the generated torque of all cylinders including the lean cylinder can be made equal while the combustion of the rich cylinder is stabilized.

[0024]

According to the present invention described above, the air-fuel ratio is switched between rich and lean at predetermined intervals until the catalyst is completed. Therefore, the oxidation target (H
(C, CO) and oxygen generated by lean combustion react in the exhaust passage, and the heat of oxidation reaction accelerates the warm-up of the catalyst. At this time, the fuel related to rich combustion is divided into a combustion donation portion and an unburned donation portion and is supplied, and the combustion donation portion fuel substantially contributes to combustion, and the unburned donation portion that is delayed is supplied. The fuel is discharged into the exhaust passage without being burned, and a necessary object to be oxidized is secured. In other words, it is possible to discharge the required oxidation target with the unburned donated fuel without substantially increasing the air-fuel ratio that is substantially involved in combustion, and the generated torque in rich combustion is lean combustion. Against a significant increase. Then, even when adjusting the generated torque in the rich combustion to the lean combustion, it is not necessary to significantly delay the ignition timing in the rich combustion, so that the catalyst is warmed up without losing the stability of the combustion. Has the effect that it becomes possible.

Further, according to the present invention, by setting the injection timing of the unburned donation portion at the overlap between the opening timing of the intake valve and the opening timing of the exhaust valve, most of the unburned donated fuel is almost exhausted. It is discharged to the exhaust passage without contributing to combustion, and has the effect of being able to secure a necessary oxidation target in promoting warm-up of the catalyst.

Further, according to the present invention, it is possible to set the injection timing of the unburned portion to be supplied just before the intake valve is closed. In this case, the fuel injected just before the intake valve is closed is burned. Most of the fuel that has adhered to the interior of the room and that has entered the gap between the piston and the cylinder is discharged into the exhaust passage without contributing to combustion, and even when the overlap period is small,
In promoting the warm-up of the catalyst, it has the effect of being able to secure the necessary oxidation target.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of the present invention.

FIG. 2 is a flowchart of basic control of the present invention.

FIG. 3 is a time chart showing the rich cylinder fuel injection of the first embodiment.

FIG. 4 is a time chart showing rich cylinder fuel injection of the second embodiment.

FIG. 5 is a characteristic diagram showing the relationship among the supply air-fuel ratio, the actual combustion air-fuel ratio, the object to be oxidized (CO + HC), the generated torque, the ignition timing, and the stability limit according to the present invention.

FIG. 6 shows a supply air-fuel ratio and an object to be oxidized (C
(O + HC), generated torque, ignition timing and stability limit.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Air Cleaner 3 Intake Duct 4 Throttle Valve 5 Intake Manifold 6 Fuel Injection Valve 7 Spark Plug 8 Exhaust Manifold 9 Exhaust Duct 10 Three-way Catalyst 11 Muffler 12 Control Unit 13 Air Flow Meter 14 Crank Angle Sensor 15 Oxygen Sensor 16 Water Temperature Sensor 17 Throttle sensor 18 Idle switch 19 Catalyst temperature sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02D 43/00 301 F02D 43/00 301H F02P 5/15 F02P 5/15 E

Claims (3)

[Claims] 1. A catalyst warm-up state detecting means for detecting a warm-up state of a catalyst provided in an exhaust pipe of an internal combustion engine, a means for detecting an operating state of the internal combustion engine, and a fuel according to an operating state of the internal combustion engine. Fuel amount calculation means for calculating the amount, ignition timing calculation means for calculating the ignition timing according to the operating state, and the fuel amount is corrected until the catalyst warm-up is completed, and the air-fuel ratio is determined every predetermined cycle. Fuel supply setting means for switching the fuel supply amount to rich and lean, a fuel dividing means for dividing the fuel supply amount set to rich into a combustion donating portion and an unburned donating portion, and an injection timing of the unburned donating portion Timing setting means set after the injection of fuel, fuel supply means for supplying fuel to each cylinder based on the set injection timing, and ignition timing correction means for retarding the ignition timing of the cylinder set to rich And characterized by having Fuel supply control device for combustion engine. 2. The injection timing of the unburned portion is set when the intake valve opening timing and the exhaust valve opening timing overlap.
The fuel supply control device for an internal combustion engine according to claim 1, wherein 3. The fuel supply control device for an internal combustion engine according to claim 1, wherein the injection timing of the unburned supply portion is set just before the intake valve is closed.