JPH0996240A - Control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a combustion condition at idle time by limiting divided injection at the idle time, in an engine dividing the fuel injection from an fuel injection valve into different times during one combustion cycle. SOLUTION: In the case of control including decision operation of divided injection or one time injection by an ECU 20, when the second injection is injected just before starting an intake stroke with the first injection prior to this second injection, first division ratio D occupied by the second injection amount relating to a total injection amount is calculated. When an idle switch 21 is placed on in an idle condition, the division ratio D is set to 100%, one time injection of only the second injection is executed. On the other hand, when the switch is not placed in the idle condition, the division ratio D is set to a value F (Ne) given as a function of an engine speed Ne. This functional value F (Ne) is set so as to decrease in accordance with increasing the engine speed, so as to attain stable combustion at idle time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an engine for a vehicle or the like, and more particularly to control of fuel injection.

[0002]

2. Description of the Related Art In an engine for a vehicle or the like, a fuel injection valve is provided in an intake system, and the injection valve controls fuel injection according to air filling efficiency at a predetermined time in each combustion cycle. For example, as disclosed in Japanese Patent Laid-Open No. 62-253936, this fuel injection may be divided into different times in one combustion cycle.

That is, this fuel injection is started immediately before the intake valve is opened because the fuel needs to be introduced into the combustion chamber during the intake stroke, and the injection amount is controlled by the pulse of the signal output to the injection valve. It is performed by adjusting the width, that is, the opening time of the injection valve.With such control, when the injection amount is large, the opening time of the injection valve becomes long, and the fuel injected immediately before the end is increased. The intake valve may be closed before it is introduced into the combustion chamber.

In order to cope with this, if the start timing of the fuel injection timing is advanced, the fuel injection is performed when the intake air amount, which is the basis of the injection amount calculation, is rapidly changing, especially during rapid acceleration. The intake air amount at the time of calculating the amount differs from the intake air amount at the start of the intake stroke, and the fuel injection amount does not correspond to the air amount actually sucked into the combustion chamber, that is, the air charging efficiency, and the intake air amount increases At the time of sudden acceleration, the fuel injection amount is calculated to be small, and there arises a problem that the air-fuel ratio becomes leaner than the target air-fuel ratio.

Therefore, the fuel injection is divided as described above. First, a predetermined amount of fuel is injected earlier than immediately before the start of the intake stroke, and then the intake air amount at that time is set immediately before the start of the intake stroke. The amount of fuel is controlled to be injected by subtracting the previously injected amount from the corresponding injection amount, and this ensures that the amount of fuel that accurately corresponds to the air charging efficiency is maintained during the opening period of the intake valve. To be introduced into.

On the other hand, the injection valve used for this kind of fuel control is opened for a time corresponding to the pulse width of the input signal as described above, and the fuel is injected during that time.
When the opening time is extremely short, for example, 1 ms (millisecond) or less, the injection amount does not correspond to the opening time, and the injection accuracy tends to deteriorate.

On the other hand, as disclosed in the above publication, in the case of split injection of fuel,
When the injection time for each injection becomes extremely short, the split injection is stopped and the fuel of an amount corresponding to the air filling efficiency is injected at the time immediately before the start of the intake stroke. That is,
In this case, since the total injection amount is originally small, the entire amount can be surely introduced into the combustion chamber before the intake valve is closed even with one injection, and divided injection is not necessary.

[0008]

By the way, in this type of engine, the combustion state tends to be unstable during idling, and it has been found that the degree thereof is related to the fuel injection timing. That is, as shown in the relationship between the fuel injection timing and the engine speed fluctuation rate in FIG. 7, the rotation is most stable and deviates from this range when the injection timing is about 120 ° before the top dead center at the start of the intake stroke. Accordingly, the rotation state or combustion state becomes unstable.

However, even in the idle state, for example, when the engine is an engine for a vehicle equipped with an automatic transmission, the automatic transmission is shifted to a driving range such as the D range, and When a load is acting on the engine, such as when the air conditioner compressor to be driven is operating, the above-mentioned split injection is performed because the fuel injection amount is relatively large. , The whole amount is 120 ° before the top dead center
The fuel cannot be injected into the front and rear ranges, and the combustion state and rotation state become unstable.

Therefore, an object of the present invention is to stabilize the combustion state and the rotation state at the time of idling by appropriately controlling the engine in which the fuel is dividedly injected.

[0011]

In order to solve the above problems, the engine control device according to the present invention is characterized by using the following means.

First, the invention according to claim 1 of the present application (hereinafter referred to as the invention)
The first invention) is to divide a fuel injection valve, an injection amount calculation means for calculating the amount of fuel injected from the injection valve, and the amount of fuel calculated by the means at different times in one combustion cycle. In an engine having injection control means for injecting fuel by means of injection, idle state detection means for detecting an idle state of the engine, and division for limiting divided injection of fuel by the injection control means when the idle state is detected by the detection means And an injection limiting means.

The invention according to claim 2 (hereinafter referred to as the second invention) includes a fuel injection valve, as in the first invention.
In an engine having an injection amount calculation means for calculating the amount of fuel injected from the injection valve, and an injection control means for dividing and injecting the amount of fuel calculated by the means at different times in one combustion cycle, Idle detecting means for detecting an idle state of the engine, and when the idle state is detected by the detecting means, and when the fuel injection amount calculated by the calculating means is equal to or less than a predetermined value, the fuel split by the injection control means. And a divided injection limiting means for limiting the injection.

The invention according to claim 3 (hereinafter, referred to as the third
In the first invention or the second invention, the divided injection is stopped when the divided injection of the fuel is limited by the divided injection limiting means.

Further, the invention according to claim 4 (hereinafter referred to as the fourth invention)
In the same manner as the first invention or the second invention, an idle switch for detecting the fully closed state of the throttle valve is used as the idle state detection means.

By using the means as described above, in any of the first to fourth aspects of the invention, the divided fuel injection is limited at the time of idling, so that the injection quantity calculated by the injection quantity calculation means is It is possible to inject the entire amount at the time when the rotation fluctuation rate shown in FIG. 7 becomes the smallest, for example, and the combustion state or rotation state at the time of idling, which tends to become unstable, becomes stable.

According to the second aspect of the invention, the above-described operation can be obtained at the time of idling, and the fuel injection amount calculated is equal to or less than the predetermined value, but not once at the time of idling, and once when the split injection is performed. If the injection time is extremely short, for example, when the vehicle is transitioning from the acceleration state to the deceleration state and the throttle valve is slightly open, the engine will not enter the idle state and On the other hand, when the air charging efficiency becomes a remarkably small value because the intake air amount is small, the split injection is limited as in the idling time.

Therefore, the combustion state and the rotation state at the time of idling are stable, and in the above cases where the fuel injection amount is small even when the engine is not idling, a high control accuracy of the injection amount can be obtained. .

According to a third aspect of the invention, in the first or second aspect of the invention, when the split injection limiting means limits the split injection of fuel, the split injection is stopped and the entire amount is injected once. Will be done. That is, the limitation of the split injection in the first and second inventions is, for example,
In the third invention, the entire amount is always injected once under a predetermined condition such as at the time of idling, though it includes the case where the injection is alternately performed at appropriate times or the frequency of divided injection is reduced. Therefore, the effects of the first and second inventions can be obtained more reliably.

According to a fourth aspect of the invention, in the first or second aspect of the invention, the idle state is detected by the idle switch for detecting the fully closed state of the throttle valve, and at that time the split injection is limited or stopped. It will be.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

As shown in FIG. 1, the combustion chamber 2 of the engine 1
Is connected to an intake passage 5 and an exhaust passage 6 via intake and exhaust valves 3 and 4, respectively.
From the upstream side, an air flow sensor 7 that detects the amount of intake air taken into the combustion chamber 2, a throttle valve 8 that controls the amount of intake air, and a fuel injection valve 9 that supplies fuel to the combustion chamber 2 are provided. Further, a catalytic converter 10 for purifying exhaust gas is installed in the exhaust passage 6.

A spark plug 11 is installed in the combustion chamber 2, and a high-voltage secondary current generated in the ignition coil 12 is rotated in the spark plug 11 in synchronization with a crankshaft (not shown). It is supplied at a predetermined time via 13 and the plug 11 is ignited.

The engine 1 is provided with a control unit (hereinafter referred to as ECU) 20 which controls the fuel injection amount from the fuel injection valve 9 and the ignition control of the ignition plug 11. The ECU 20 has a control unit 20. , A signal indicating the intake air amount from the air flow sensor 7, a signal from the idle switch 21 for detecting the fully closed state of the throttle valve 8, and a rotation angle (crank angle) of a crankshaft attached to the distributor 13. A signal from the crank angle sensor 22 to be detected and the residual oxygen concentration in the exhaust gas in the exhaust passage 6 are detected to detect the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 2.
₂₎ The signals from the sensor 23 are input, and the fuel injection control and the ignition control are performed based on these signals.

Next, as the operation of this embodiment, the above E
The fuel injection control by the CU 20, in particular, the control operation including the operation of determining split injection or single injection will be described with reference to the flowcharts of FIG.

First, the flow chart of FIG. 2 shows the main routine of the control of the engine 1. In this routine, first in step S1, the air flow sensor 7, the idle switch 21, and the crank angle sensor 2 shown in FIG.
2 and the signal from the O ₂ sensor 23, and then
In step S2, the engine speed Ne is calculated based on the signal from the crank angle sensor 22, and in step S3
The engine speed Ne and the air flow sensor 7
The air charging efficiency Ce is calculated based on the intake air amount indicated by the signal from.

Next, in step S4, the fuel injection division ratio D is calculated, and in step S5, the injection amounts T of the first and second injections at the calculated division ratio D are calculated. here,
The second injection is an injection that is performed immediately before the start of the intake stroke, the first injection is an injection that is performed before that (see FIG. 6), and the division ratio D is the ratio of the second injection amount to the total injection amount. Is shown. Therefore, D = 100%
At this time, the first injection is lost and only the second injection is performed once.

Next, the division ratio D in steps S4 and S5 described above.
Specific operations of the calculation control of and the calculation control of the fuel injection amount T will be described.

First, the calculation control of the division ratio D is performed according to the subroutine shown in the flow chart of FIG. 3. First, in step S11, it is determined whether or not the idle switch 21 is ON, that is, the throttle valve 8 is in the fully closed idle state. If it is in the idle state, the division ratio D is set to 100% in step S12. If it is not in the idle state, the division ratio D is set to the engine speed Ne in step S13. It is set to a value F (Ne) given as a function.

In this case, this function value F (Ne) is set so as to decrease as the engine speed Ne increases, as shown in FIG. If the injection amount of the second injection performed immediately before is large, the intake valve 3 is not fully introduced before being introduced into the combustion chamber 2.
Is to be closed.

The calculation control of the fuel injection amount T is performed according to the subroutine shown in the flow chart of FIG. 5. In this control, the feedback correction amount Cfb is first calculated in step S21, and then the feedback correction amount is calculated in step S22. Amount Cfb and air-fuel ratio correction coefficient Caf
Then, the injection time Ta is calculated according to the following equation using the current air filling efficiency Ce and the width of the injection pulse, that is, the conversion coefficient Kp for converting these values into the injection time Ta.

Ta = Kp · Ce · Caf · (1.0 + Cfb) Here, regarding the feedback correction amount Cfb, the signal from the O ₂ sensor 23 indicates that the air-fuel ratio of the air-fuel mixture in the combustion chamber 2 is richer than the theoretical air-fuel ratio. When it indicates that the air-fuel ratio is a negative value, the fuel injection amount is decreased, and when it indicates a lean condition, the fuel injection amount is a positive value and the fuel injection amount is decreased, so that the air-fuel ratio converges to the theoretical air-fuel ratio. It is for feedback control so as to make it. Further, the air-fuel ratio correction coefficient Caf is the feedback correction amount C
This is a coefficient that determines the degree when the feedback control to the stoichiometric air-fuel ratio is stopped with fb set to 0 and the enrichment control that makes the air-fuel ratio richer than the stoichiometric air-fuel ratio is performed.

Then, in step S23, it is determined based on the signal from the crank angle sensor 22 whether or not the present time is the time when the preset first injection should be performed as shown in FIG. When it is the first injection timing, in step S24, the value obtained by integrating the division ratio D calculated as described above and the calculated injection time Ta, that is, the temporary injection time of the second injection expected at the first injection timing ( Ta * D) is determined to be smaller than 1 ms. And 1m
If not smaller than s, in step S25, the calculated injection time Ta to the temporary injection time of the second injection (Ta × D)
The value obtained by subtracting is the injection time Ta1 of the first injection, and
When the temporary injection time (Ta × D) of the second injection becomes smaller than 1 ms, the time obtained by subtracting 1 ms from the calculated injection time Ta is set as the injection time Ta1 of the first injection in step S26. That is, when the tentative injection time (Ta × D) of the second injection does not become smaller than 1 ms, the value is kept as it is,
When it becomes smaller, 1 ms is set as this temporary injection time, and the value obtained by subtracting this from the calculated injection time Ta is set as the injection time Ta1 of the first injection.

Next, in step S27, the above step S
25 or step S26 is subtracted to determine whether the injection time Ta1 of the first injection is shorter than 1 ms. If it is smaller, the injection time Ta1 of the first injection is set to 0 ms in step S28, and the step S29 is performed. In addition, the final injection time T is also set to 0 (ms), and when the injection time Ta1 of the first injection does not become smaller than 1 ms, in step S30, at the time Ta1, due to the characteristics of the fuel injection valve 9,
The required invalid injection time Tv is added, and the value is set as the final injection time T.

On the other hand, when the present time is not the time when the first injection should be performed, the above steps S23 to S31 are performed.
Is executed to determine whether or not the present time is the time when the preset second injection should be performed as shown in FIG. 6, and if it is this time, in step S32, from the calculated injection time Ta to the above step. S25, step S26 or step S
The value obtained by subtracting the injection time Ta1 of the first injection obtained in 28 is set as the injection time Ta2 of the second injection. In this case, the calculated injection time Ta is obtained in step S22 at the injection timing of the second injection, and thus is obtained in step S22 at the injection timing of the first injection and used in the calculations of steps S24 to S26. The value is generally a different value.

Then, in step S33, it is determined whether the injection time Ta2 of the second injection is shorter than 1 ms,
When it becomes smaller, the injection time Ta2 of the second injection is set to 1 ms in step S34, and the invalid injection time Tv is added to the time Ta2 in step S35 to obtain the final injection time T.

As described above, the final injection time T of the first and second injections is calculated, and the fuel injection valve 9 is opened during that time to inject fuel at each timing. In that case, Since the total injection amount corresponds to the calculated injection time Ta calculated at the injection timing of the second injection, the fuel supply amount accurately corresponds to the required amount and the injection time is 1 ms.
When it becomes smaller, the injection is stopped for the first injection and set to 1 ms for the second injection, so that deterioration of accuracy due to extremely short injection time is avoided.

Then, particularly during idling, the split injection is unconditionally stopped, and the entire amount of the calculated injection amount is injected immediately before the start of the intake stroke.

[0039]

As described above, according to the present invention, in an engine in which the fuel injection from the fuel injection valve is divided into different times in one combustion cycle, the divided injection is performed at idle. Since the limitation is made, it becomes possible to inject the total amount of the required fuel at an optimum timing, for example, at the time when the rotation fluctuation rate becomes the smallest, especially at the idle time when the combustion state or the rotation state tends to be unstable. . This stabilizes the combustion state or rotation state during idling.

[Brief description of drawings]

FIG. 1 is a control system diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control main routine of the embodiment.

FIG. 3 is a flowchart showing a division ratio calculation subroutine used in the control.

FIG. 4 is a map similarly showing the characteristics of the division ratio.

FIG. 5 is a flow chart showing a subroutine for similarly calculating a fuel injection amount.

FIG. 6 is a time chart which similarly shows the injection timing of divided injection.

FIG. 7 is an explanatory diagram showing a general relationship between a fuel injection timing and an engine rotation fluctuation rate.

[Explanation of symbols]

1 engine 9 fuel injection valve 20 injection amount calculation means, injection control means, split injection restriction means (ECU) 21 idle state detection means (idle switch)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Gota 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (4)

[Claims] 1. A fuel injection valve, injection amount calculation means for calculating the amount of fuel injected from the injection valve, and injection of the amount of fuel calculated by the means at different times in one combustion cycle. A control device for an engine, comprising: an injection control means for controlling the idle state of the engine; and an idle state detection means for detecting an idle state of the engine; A control device for an engine, comprising: a split injection limiting means for limiting. 2. A fuel injection valve, an injection amount calculation means for calculating the amount of fuel injected from the injection valve, and the amount of fuel calculated by the means is divided and injected at different times in one combustion cycle. And a fuel injection amount calculated by the calculation means when an idle state is detected by the detection means and an idle detection means for detecting an idle state of the engine. A control device for an engine, comprising: split injection limiting means for limiting split injection of fuel by the injection control means when the value is equal to or less than a predetermined value. 3. The engine control device according to claim 1, wherein the split injection limiting means suspends the split injection when limiting the split injection of fuel. 4. The engine control device according to claim 1, wherein the idle state detection means is an idle switch that detects a fully closed state of the throttle valve.