JPH06213036A - Fuel injection controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a misfire cylinder from misfiring in succession and keep off any increase in the discharge of unburnt fuel at this time, in an internal combustion engine fuel injection controller. CONSTITUTION:This controller is provided with a first fuel supply means 5 supplying a combustion chamber 1 with fuel so as to form a uniform air-furl mixture there, and a second fuel supply means 5 supplying the fuel so as to make the mixture to be formed in and around a spark plug 4 of the combustion chamber 1 become a rich air-fuel ratio as compared with an air-fuel mixture to be formed in another part in the combustion chamber 1. In addition, it is provided with a first control means 6, executing the fuel supply by means of the first fuel supply means 5 at the time of engine starting, a misfire detecting means 8 detecting a misfire at the engine starting, and a second control means 6 executing the fuel supply after reducing the supply to such a cylinder as being detected of the misfire by this misfire detecting means 8 by means of the second fuel supply means 5, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 61-250354 discloses
It has a first injection valve for injecting fuel into the intake passage and a second injection valve for directly injecting fuel into the combustion chamber, and has a first injection valve when the engine is started.
A homogeneous fuel-air mixture combustion is performed using an injection valve, a stratified mixture combustion is performed using a second injection valve when the load is low after engine warm-up, and a high load after warm-up is performed. Describes an internal combustion engine that uses both injection valves to supply a large amount of fuel to perform homogeneous mixture combustion.

In this internal combustion engine, homogeneous mixture combustion at the time of starting the engine is intended to completely burn the fuel to reduce the emission amount of unburned fuel, and to reduce the load after the engine is warmed up. Stratified combustion at the time is intended to reduce fuel consumption by performing fuel injection so that a rich air-fuel mixture is formed only near the spark plug, and reducing the fuel injection amount as a whole. The homogeneous air-fuel mixture combustion at the time of high load is intended to obtain high torque by realizing complete combustion with a large amount of fuel.

[0004]

Generally, at the time of starting the engine, the ignitability is poor and the misfire is likely to occur as compared with the operation after the engine is warmed up. In the above-mentioned conventional technique, when a misfire occurs at the time of engine start, most of the fuel supplied to the cylinder as an air-fuel mixture is discharged as it is, but a part of it remains in the combustion chamber, and a similar fuel supply is performed next time. When this is done, the air-fuel mixture formed in the combustion chamber becomes richer than the desired air-fuel ratio, and the ignitability is improved, but complete combustion does not occur and the amount of unburned fuel discharged increases. to solve this problem,
It is conceivable to simply reduce the amount of fuel injected into the misfiring cylinder by the amount remaining in the combustion chamber, but there is a possibility of continuous misfiring as in the previous case.

Therefore, an object of the present invention is to prevent the misfiring cylinders from continuously misfiring in a homogeneous mixture combustion at the time of starting the engine, and to prevent an increase in the amount of unburned fuel discharged at this time. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can achieve the above.

[0006]

A fuel injection control apparatus for an internal combustion engine according to the present invention comprises a first fuel supply means for supplying fuel so that a uniform mixture is formed in a combustion chamber, and a vicinity of a spark plug in the combustion chamber. Second fuel supply means for supplying fuel such that the air-fuel mixture formed in the air-fuel mixture has a richer air-fuel ratio than the air-fuel mixture formed in the other part of the combustion chamber, and the first fuel supply when the engine is started. Means for executing fuel supply by means, misfire detection means for detecting misfire when the engine is started, and the cylinder for which misfire is detected by the misfire detection means is supplied with the second fuel supply means by the second fuel supply means next time. And a second control means for reducing the fuel supply.

[0007]

In the above-described fuel injection control device for an internal combustion engine, the first control means causes the first fuel supply means to perform fuel supply at the time of engine start-up to form a uniform air-fuel mixture in the combustion chamber. However, when the misfire detection means detects the misfire at the time of starting the engine, the second control means causes the cylinder to perform the next fuel supply by the second fuel supply means, and at this time, in order to reduce the fuel supply amount, the combustion chamber is A desired amount of fuel is supplied together with the fuel remaining due to misfire, and the air-fuel mixture formed near the ignition plug in the combustion chamber has a richer air-fuel ratio than the air-fuel mixture formed in other parts. Becomes

[0008]

1 is a schematic sectional view of an internal combustion engine equipped with a fuel injection control device according to the present invention. In the figure, 1 is a combustion chamber, 2 is an intake passage, and 3 is an exhaust passage.
An ignition plug 4 and an injection valve 5 for injecting fuel in the vicinity of the ignition plug 4 are installed above the combustion chamber 1.

The control device 6 for executing the fuel injection control of the injection valve 5 includes a rotation sensor (not shown) for detecting the engine speed, a cooling water temperature sensor 7 for detecting the cooling water temperature as the engine temperature, and an intake passage. 3, an air flow meter (not shown) provided upstream, a pressure sensor 8 for detecting the combustion pressure in the combustion chamber 1, and the like are connected. The above-described fuel injection control is performed according to the first flowchart shown in FIG. 2 and the second flowchart shown in FIG. The first flow chart is executed every time the intake stroke of a specific cylinder starts from the ON signal of the starter. The second flowchart is executed every time the intake stroke of each cylinder starts from the ON signal of the starter, and particularly shows the case of a four-cylinder engine.

The first flow chart will be described. First, at step 101, an engine speed N detected by a rotation sensor, an intake air amount Q detected by an air flow meter, and a cooling water temperature T detected by a cooling water temperature sensor 7.
The fuel injection amount τ is determined so that a desired air-fuel ratio can be obtained according to the engine operating state determined from the above. Next step 1
In 02, it is determined whether or not the engine speed N is equal to or higher than the predetermined speed N1 indicating the complete explosion state. When the determination is affirmative, the routine proceeds to step 103, where 0 is substituted into the flag F.

On the other hand, when the determination in step 102 is denied, that is, before the complete explosion of the engine, step 10
In step 4, the count value M is incremented by 1. The count value M is reset to 0 when the engine is stopped. Next, at step 105, it is judged if the count value M is 1. This determination is affirmative only in the first processing, and the flag F is set to 2 in step 106.
Is substituted, but is denied from the next time (the second and subsequent injections), and 1 is substituted in the flag F in step 107.

Next, the second flow chart will be described. First, at step 201, the cylinder discrimination value n is incremented by 1. The cylinder discrimination value n is reset to 0 when the engine is stopped. Next, at step 202, it is judged if the cylinder discrimination value n is larger than 5. When this determination is negative, it is as it is, and when it is affirmative, the cylinder discrimination value n is set to 1 in step 203, and the routine proceeds to step 204.

In step 204, it is determined whether the flag F is 1. The flag F is set to 2 only in the first process of the first flow chart, the determination at step 204 is initially denied, and the routine proceeds to step 205, where the fuel injection amount at the beginning of the intake stroke is performed for the cylinder whose cylinder determination value is n. Fuel injection at τ is performed. Next, at step 206, it is judged if the flag F is 0 or not. Since the present flag F is 2, this determination is denied and the routine proceeds to step 210.

In step 210, the cylinder discrimination value is n.
The combustion pressure P is detected by the pressure sensor 8 of the cylinder No., and it is determined whether the pressure P is equal to or higher than a predetermined value P1. If the engine burns without causing a misfire, this determination is affirmative and the routine proceeds to step 211, where the cylinder misfire determination flag Jn is 0.
Is substituted. On the other hand, if a misfire has occurred, this determination is denied, and 1 is assigned to the cylinder misfire determination flag Jn.

This series of processing is performed only once for all the cylinders, and since the flag F is set to 1 in the first flow chart thereafter, the determination at step 204 is affirmative and the routine proceeds to step 207. Step 207
In, it is determined whether the cylinder misfire determination flag Jn is 1, that is, whether the cylinder currently in the intake stroke has misfired in the previous explosion stroke.

If this determination is denied, step 205
The processing proceeds to step 205 and the processing after step 205 described above is executed. When the determination is affirmative, the processing proceeds to step 208.
In step 208, a new fuel injection amount τ is obtained by subtracting the fuel amount α remaining in the combustion chamber 1 due to misfire from the fuel injection amount τ currently determined in the first flowchart.
Is determined. Next, at step 209, fuel injection with a new fuel injection amount τ is executed at the end of the compression stroke for the cylinder with the cylinder discrimination value n. Next, the misfire determination for each cylinder is performed after step 210.

In the first flow chart, the flag F is set to 0 when the engine is in the complete explosion state, so step 20
After fuel injection at the beginning of the intake stroke in step 5, step 2
The determination in 06 is affirmed, and the misfire determination process for each cylinder after step 210 is omitted and the process ends.

According to such fuel injection control, after the complete combustion of the engine, the fuel injection with the fuel injection amount τ determined by the engine operating state is performed in the early stage of the intake stroke of each cylinder, and the injected fuel is By ignition at the end of the compression stroke, the intake air is sufficiently mixed with the intake air to form a uniform air-fuel mixture, which can be completely combusted to obtain high torque.

Even before the complete explosion of the engine, the same fuel injection is normally performed, and the injected fuel is completely burned to reduce the amount of unburned fuel discharged. However, before the complete explosion of the engine, the engine is in an operating state where misfire is likely to occur, and if a cylinder misfires, an unburned air-fuel mixture remains in the combustion chamber 1 at the start of the intake stroke. When the fuel injection is executed as usual in the early stage of the intake stroke, the homogeneous mixture formed at the ignition time becomes richer than the desired air-fuel ratio. This mixture ignites well,
Since it does not burn completely, the amount of unburned fuel emitted increases.

In order to prevent the increase in the amount of unburned fuel discharged, it is considered that the amount of fuel injection is simply reduced so that a uniform air-fuel mixture having a desired air-fuel ratio is formed, but misfire may occur again. There is a nature. In this embodiment, in any cylinder before the complete explosion of the engine, if misfiring with a homogeneous mixture occurs,
Since the next fuel injection amount to this cylinder is reduced by a predetermined amount from that determined by the engine operating state, the amount of fuel remaining in the combustion chamber 1 of this cylinder at the start of the intake stroke is greater than necessary. Are no longer present in the combustion chamber 1 and the amount of unburned fuel discharged is prevented from increasing. Further, at this time, the fuel supplied from the injection valve 5 is not injected into the vicinity of the spark plug 4 at the end of the compression stroke and thus does not become a uniform air-fuel mixture but forms a rich air-fuel mixture only in the vicinity of the spark plug 4. As a result, reliable ignition is realized in the next explosion stroke of the misfiring cylinder, and continuous misfiring of this cylinder is prevented. This misfire determination of the stratified mixture combustion is executed for the purpose of confirmation, and if the misfire occurs also this time, the stratified mixture combustion with good ignitability is continuously executed next time.

In this embodiment, in order to simplify the explanation, the fuel amount α remaining in the combustion chamber 1 due to misfire is a constant. However, strictly speaking, the lower the engine temperature, the poorer the atomized state of the injected fuel and the more likely it is to adhere to the top surface of the piston, etc. A large amount remains in the room.
Therefore, a better fuel injection control is realized by making the fuel amount α a variable that becomes larger as the cooling water temperature becomes lower. Further, the combustion pressure by the pressure sensor is used to determine the misfiring cylinder, but in addition, changes in engine speed before and after the explosion stroke of each cylinder, measurement of explosion sound, measurement of vibration due to explosion, and exhaust gas For example, temperature measurement can be used.

In this embodiment, a single injection valve 5 is used and the injection timing is changed to form a homogeneous mixture and a stratified mixture in the combustion chamber 1. However, in the present invention, for example, a first injection valve that injects fuel into the intake passage to form a homogeneous mixture and a second injection valve that injects fuel directly into the combustion chamber to form a stratified mixture. It can also be applied to an internal combustion engine having a.

[0023]

As described above, according to the fuel injection control device for an internal combustion engine of the present invention, as in the conventional case, the homogeneous mixture combustion is executed at the time of starting the engine to completely burn the fuel,
Reduce unburned fuel emissions. However, if a misfire occurs in this homogeneous mixture combustion, the cylinder will perform a stratified mixture combustion next time, and the ignitability will be improved, so continuous misfire is prevented. At this time, the fuel injection amount is reduced in consideration of the amount of fuel remaining in the combustion chamber due to misfire, so there is no more fuel than necessary in the combustion chamber, and the amount of unburned fuel discharged increases. Is prevented.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an internal combustion engine equipped with a fuel injection control device according to the present invention.

FIG. 2 is a first flowchart for fuel injection control.

FIG. 3 is a second flowchart for fuel injection control.

[Explanation of symbols]

 1 ... Combustion chamber 2 ... Intake passage 3 ... Exhaust passage 4 ... Spark plug 5 ... Injection valve 6 ... Control device 8 ... Pressure sensor

Claims (1)

[Claims] 1. A first fuel supply means for supplying fuel so that a uniform air-fuel mixture is formed in the combustion chamber, and an air-fuel mixture formed in the vicinity of the ignition plug of the combustion chamber is formed in another portion of the combustion chamber. Second fuel supply means for supplying fuel so that the air-fuel ratio becomes richer than that of the air-fuel mixture, first control means for executing fuel supply by the first fuel supply means at engine start, and at engine start-up In the above, there is provided misfire detecting means for detecting misfire, and second control means for causing the cylinder in which misfire is detected by the misfire detecting means to execute the fuel supply by reducing the supply amount by the second fuel supply means next time. A fuel injection control device for an internal combustion engine, comprising: