JPH0742887B2 - Engine combustion control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine combustion control device for improving combustion stability of an engine.

(Prior Art) Whether the combustion state of the engine is good or bad, that is, whether the combustion is good or bad has various influences not only on the output of the engine but also on the ratio of harmful components in the exhaust gas. . It is known that the good and bad of this combustion are alternately repeated. That is, exhaust residual gas is inevitably generated in the combustion chamber, but when good combustion is performed, it is almost complete combustion, so there are many inert gases that control combustion in the exhaust residual gas. In a state called internal EGR,
When the next combustion becomes worse, or when the bad combustion is performed, HC is increased in the residual exhaust gas as a pre-existing component because it is an incomplete combustion, so that the next combustion is favorably performed.

Therefore, as shown in JP-A-51-54125, for example, by using an ion electrode, it is possible to discriminate the magnitude of the combustion speed, that is, whether the combustion is good or bad (the higher the combustion speed, the better the combustibility). Therefore, it has been proposed to correct the operation of the exhaust gas purifying device based on the quality of combustion.

(Problems to be solved by the invention) By the way, recently, optimization of engine control is desired, but various controls such as exhaust gas purification are individually performed based on the goodness of combustion described above. Therefore, it is impossible to deal with all cases. In particular, since an engine in which such good or bad combustion is a problem is generally run lean, it is fundamentally necessary to prevent the good or bad combustion from occurring, that is, to improve combustion stability. Will be desired.

Therefore, it is an object of the present invention to provide an engine combustion control device capable of improving combustion stability by preventing the occurrence of good and bad combustion as much as possible.

(Means and Actions for Solving Problems) In the present invention, in the next combustion stroke when good combustion is performed, bad combustion occurs, and in the next combustion stroke when bad combustion is performed, Focusing on the point that good combustion is achieved, whether the combustion state is good or bad is discriminated, and control that improves the combustibility is prospectively performed in the combustion process where bad combustion will occur. Specifically, as shown in FIG. 1, combustion adjustment means for adjusting factors affecting the combustion state of the engine, combustion detection means for detecting the combustion state of the engine, and detection by the combustion detection means The combustion state is a combustion state that is better than the reference combustion state as a predetermined determination criterion, but a combustion determination means that determines whether the combustion state is worse than the reference combustion state, and the combustion determination means are better. When it is determined that the combustion state is in the combustion stroke of the next cycle, and when it is determined by the combustion determination means that the combustion state is bad, the combustion state is improved in the combustion stroke of the next cycle. And a combustion control means for controlling the combustion adjusting means.

With such a configuration, the combustion state is controlled so as to fall within the range of the determination criteria by the combustion determination means, the difference between the good state and the bad state of combustion is minimized, and the combustion stability is improved. Will be improved.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

In FIG. 2, reference numeral 1 is an engine body having a multi-cylinder,
In the intake passage 3 connected to the intake port 2, an air cleaner 4, an air flow sensor 5, a throttle valve 6, a surge tank 7, and a combustion injection valve 8 are sequentially arranged from the atmosphere side. The intake passage 3 upstream of the surge tank 7 serves as a single common passage 3A, while the surge tank 7
The intake passages on the further downstream side are individually formed as independent passages 3B connected to the intake ports, and the combustion injection valves 8 are individually arranged in the independent passages 3B. In addition, an exhaust passage communicating with the exhaust port 9
An exhaust gas purification device 11 including a three-way catalyst is arranged at 10.

The intake port 2 is provided by an intake valve 12 and the exhaust port 9 is also provided.
The exhaust valve 13 opens and closes at a known timing,
In each combustion chamber 14 where the intake / exhaust ports 2 and 9 are open,
An ignition plug 15 and an ion sensor (ion electrode) 16 constituting a combustion detecting means are individually arranged at a predetermined distance from each other. It should be noted that this ion sensor 16 is normally in a specific conduction state when a predetermined voltage is constantly applied as described in the above-mentioned JP-A-51-54125, but it is conducted in a combustion gas atmosphere. It is a state. Then, by measuring the time from when the ignition plug 15 is ignited until the ion sensor 16 is brought into a conductive state, it is possible to know the combustion speed, that is, whether the combustion state is good or bad.

In FIG. 2, reference numeral 21 denotes a control unit. In addition to the signals from the air flow sensor 5 and the ion sensor 16, signals from the sensors 22 to 26 are input to the control unit 21, while the control unit 21 Is output to the spark plug 15 and the combustion injection valve 8. The respective sensors 22 to 26 will be described. The sensor 22 is a throttle sensor that detects the opening position of the throttle valve 6. The sensor 23 is an intake pressure sensor that detects the intake pressure of the independent passage 3B, that is, the engine load. The sensor 24 is a water temperature sensor that detects the engine cooling water temperature. Sensor 25
Is substantially composed of a distributor and detects the engine speed and the crank angle position.
The sensor 26 is essentially a starter switch that is closed when the engine is started, and detects whether or not the engine is being started.

The control unit 21 is composed of, for example, a microcomputer, and its function will be described below with reference to the flowchart shown in FIG. It should be noted that in the embodiment, the combustion injection amount is used as a factor for adjusting the combustibility, that is, the combustion state, and the correction of the combustibility improvement (correction of the combustion injection amount) performed as necessary after detection of the good or bad of the combustion is performed. ,
The flag is used to determine whether to perform in the next combustion stroke or in the next combustion stroke. When the flag is 1, it means correction in the next combustion stroke. It has become a thing.

Based on the above, first, the steps in FIG.
Various control values are initialized in S1, and the flag is set to 0 in this initialization. Next, in step S2, each of the sensors 5, 16, 22 to 26
The output signal from is read, and based on the read data, in step S3, various target control values Do, Tθ,
Ft and Ig are read from the specified map. Of these control values, Do is a duty ratio for duty-controlling the fuel injection valve 8 and corresponds to the fuel injection amount. Basically, for example, the engine speed and the intake air amount are It is decided based on. Tθ is a reference combustion speed when the combustion state is good, and is determined by, for example, the engine speed and the engine load. Ft is a combustion injection timing, which is an independent injection type in which combustion burning is performed according to the intake stroke of each cylinder, and is determined by, for example, the engine speed and the engine load. Ig is the ignition timing and is determined by, for example, the engine speed and the engine load.

After step S3, the process proceeds to step S4, where it is determined whether or not the combustion speed is within the control range. The states other than this control range include an operating range in which the combustion injection amount is corrected, for example, when the engine is cold, during and immediately after starting the engine, during acceleration and deceleration, as well as in a high rotation range and a high load range. In other words, in the embodiment, the control range is a low load and low speed range in which the engine operates in a stable operating state, and particularly in this control range, so-called lean operation is performed. ing.

When it is determined in step S4 that it is not in the control range,
In step S5, the duty ratio Do set in step S3 is set to the final duty ratio D. After this, wait for the predetermined fuel injection timing in step S6,
At the time when the predetermined fuel injection timing is reached, the final duty ratio D is output to the fuel injection valve 8 in step S7. After this, after waiting for the predetermined ignition timing in step S8, when the predetermined ignition timing is reached, output processing, that is, ignition of the spark plug 15 is performed in step S9.

On the other hand, when it is determined in step S4 that it is in the control range, the actual combustion speed T is calculated in step S10. Of course, this actual burning speed T is
This is the time from the time when the ignition is performed on 15 to the time when the flame reaches the ion sensor 16 and the ion sensor 16 is turned on.

After step S10, it is determined in step S11 whether or not the absolute value of the difference between the actual combustion speed T and the reference combustion speed Tθ is equal to or less than a predetermined allowable value (dead zone) a. If the absolute value of the difference between the two is less than or equal to a, it means that the combustion speed is within the allowable range.
After shifting to S12, the duty ratio Do in step S3 is set as the final duty ratio D, and then in step S13.
After the flag is set to 0 in, the processing of step S6 and subsequent steps is performed.

When it is determined in step S11 that the absolute value of the difference between T and Tθ is not less than or equal to a, the process proceeds to step S14, and whether or not the actual combustion speed T is smaller than Tθ-a,
That is, it is determined whether the combustion speed is too fast. When it is determined that T <Tθ-a, the combustion speed in the next combustion stroke is slow (bad combustion). Therefore, in order to correct this, that is, the combustion state is improved. In step S15, Do in step S3
The final duty ratio D is set by adding the duty ratio ΔD for the correction to. After this, after the flag is set to 0 in step S16, the processes in step S6 and subsequent steps are performed.

Further, when it is determined in step S14 that T <Tθ-a is not satisfied, T> Tθ-a is satisfied, and the combustion speed T is too slow. In this case, step S17
Then, it is determined whether or not the flag is 1, but since the flag is initially initialized to 0, the process proceeds from step S17 to step S18, where the step is performed.
After the duty ratio Do in S3 is set as the final duty ratio D, the flag is sequentially set to 1 in step S19, the actual value of the combustion speed T is held in step S20, and the processing from step S6 onward is performed. It When the processing from step S20 to step S6 is performed, step S2
Since T is held at 0, the process proceeds to step S17 again regardless of the calculation at step S10. At this time, however, since the flag is set to 1 at step S19, the process proceeds from step S17 to step S21. Will be migrated. Then, in step S21, Do + △ is used to increase the combustion speed.
After setting D to the final duty ratio D (corresponding to step S15), the flag is set to 0 in step S22, and further step S
After canceling T in step 23 (releasing the hold in step S20), the processing from step S6 is performed.

The above matters will be described below with reference to FIGS. 4 to 8.

When the actual combustion speed T is within the allowable range, the route goes through steps S11 to A13, and FIG. 4 (a)
Equivalent to. At this time, since the combustion speed is neither too fast nor too slow, the combustion is performed in the next combustion stroke without any correction of the combustion injection amount that affects the combustibility. That is, as shown in FIG. 5, as in the next combustion stroke C ₂ of the combustion stroke C ₁ the actual combustion rate T is detected, it will have similar combustion and the combustion stroke C ₁ is carried out , The fuel injection amount is not corrected.

When the actual combustion speed T is too fast, this is the route from step S14 to step S16.
It corresponds to FIG. In this case, the combustion speed will be slower (bad combustion) in the next combustion process C ₂ after the combustion process C ₁ in which the combustion speed T is detected.
In order to improve the combustibility in the next combustion stroke C ₂ , the fuel injection amount is increased by ΔD, and the flag is set to 0 in step S16 in order to perform this increase in the next combustion stroke C ₂ ( (See Figure 6).

This is a route that goes through step S17 when the actual combustion speed T is too slow, and corresponds to FIG. 4 (c). In this case, as shown in FIG. 7, the combustion speed is too fast in the combustion process C ₂ subsequent to the combustion process C ₁ in which the combustion speed T is detected. Therefore, first, step S18
By the process that goes through, the correction in the next combustion stroke C ₂ is not performed, while the flag is used to perform the next combustion stroke.
At C ₃ , the combustion injection amount is increased by ΔD to accelerate the combustion speed.

By the feedback control of the combustion speed as described above, the combustion speed is controlled so as to be converged within the allowable range.
A state in which this control is stable (converged) is shown in FIG. That is, after the control becomes stable, each combustion stroke C ₁ ,
C _2, C _3, always burn rate in C ₄ · · · · · it is assumed within the allowable range.

Although the embodiment has been described above, there are various factors such as ignition timing, intake air amount, swirl strength, etc. as factors that affect the combustion state. It can be adjusted and controlled. In the case of a diesel engine, for example, the fuel injection timing may be adjusted and controlled. Further, for detecting the goodness or badness of combustion, an appropriate method can be adopted, for example, by observing the combustion pressure. Of course,
When the control unit 21 is composed of a microcomputer, it may be either a digital type or an analog type.

(Effects of the Invention) As is clear from the above description, the present invention can improve combustion stability itself. As a result, it becomes unnecessary to separately perform various controls based on the quality of combustion, which is extremely advantageous in obtaining optimum control of the engine.

[Brief description of drawings]

FIG. 1 is an overall block diagram of the present invention. FIG. 2 is an overall system diagram showing an embodiment of the present invention. FIG. 3 is a flowchart showing a control example of the present invention. 4 to 8 are diagrams schematically showing the control contents of the flowchart shown in FIG. 1: Engine body 8: Fuel injection valve (combustion adjusting means) 15: Spark plug 16: Ion sensor (combustion detecting means) 21: Control unit

Claims (1)

[Claims] 1. A combustion adjusting means for adjusting a factor affecting a combustion state of an engine, a combustion detecting means for detecting a combustion state of the engine, and a combustion state detected by the combustion detecting means are predetermined. Combustion determination means for determining whether the combustion state is better than the reference combustion state as the determination criterion or is worse than the reference combustion state, and the combustion determination means determines that the combustion state is good. When in the combustion stroke of the next cycle, and when the combustion determination means determines that the combustion state is bad, the combustion adjustment means is controlled to improve the combustion state in the combustion stroke of the next cycle. A combustion control device for an engine, comprising: