JPH0535260B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an internal combustion engine, and particularly to an air-fuel ratio control device for a lean-burn engine that performs combustion with a mixture leaner than the stoichiometric air-fuel ratio.

(Technical background) With the tightening of exhaust gas regulations for automobile internal combustion engines, a three-way catalyst is installed in the exhaust system to reduce the
The exhaust gas is purified by oxidizing HC and CO and reducing NOx.

Such a device is shown in FIG. A three-way catalyst reduces NOx when the air-fuel mixture is near the stoichiometric air-fuel ratio.
Both HC and CO oxidation functions can be maximized.

Therefore, an oxygen sensor 3 that changes stepwise around the stoichiometric air-fuel ratio is attached to the exhaust pipe 2 upstream of the three-way catalyst 4, and based on the signal from this oxygen sensor 3,
The control unit 5 performs feedback control on the amount of fuel supplied from the fuel injection valve 1 so that an air-fuel mixture near the stoichiometric air-fuel ratio is always obtained.

However, recently, in addition to cleaning exhaust gas, there is a need to reduce engine and fuel efficiency from the viewpoint of resource conservation, and in order to achieve these two goals at the same time, it is necessary to
It is advantageous to operate the engine in a mixture range leaner than the stoichiometric air-fuel ratio, and such a device has been proposed (see, for example, Japanese Patent Laid-Open No. 140449/1983).

Therefore, when trying to perform feedback control by applying the oxygen sensor 3 described above to a lean burn engine, the detection accuracy of the oxygen sensor 3 is only high near the stoichiometric air-fuel ratio, so if the air-fuel ratio deviates significantly from the stoichiometric air-fuel ratio, This makes stable feedback control difficult.

In addition, since the air-fuel ratio set in the intake system is detected in the exhaust system, it is unavoidable that there will be a response delay in detection, and in actual control, this response delay must be taken into account. Must be. Therefore, especially during acceleration, the response delay increases and fluctuations from the set air-fuel ratio tend to occur, resulting in deterioration of fuel efficiency and exhaust emissions.

(Objective of the Invention) The present invention directly detects a parameter representing the combustion state in the fuel chamber, which is closely related to the air-fuel ratio, and uses this detection signal to perform feedback control of the air-fuel ratio. High control accuracy,
Another object of the present invention is to provide an air-fuel ratio control device with high responsiveness.

Furthermore, in the second invention, in addition to the first invention, in-cylinder gas flow is appropriately generated, improving fuel efficiency and NOx
It is an object of the present invention to provide an air-fuel ratio control device that simultaneously satisfies the regulatory values for emissions such as the following.

(Disclosure of the Invention) FIG. 2 is an overall configuration diagram for clearly showing the configuration of the present invention.

The fuel supply control means is a basic injection amount calculation means 2.
5, a drive means 26, and a fuel supply means 16.

That is, the basic injection amount calculation means 25 calculates the basic injection amount based on the engine speed and engine load so that a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio is obtained, and based on the calculation result, the driving means 26 drives the fuel supply means 16 to supply fuel to the engine.

The engine speed is detected by a rotation speed detection means 11 (for example, a rotation sensor such as a crank angle sensor), and is detected by an engine load detection means 12 (for example, an intake negative pressure sensor, an air flow meter).

Further, the fuel supply means 16 is constituted by a fuel injection device in a fuel injection type engine, and an electronically controlled carburetor in a carburetor type engine.

In this case, the fuel injection device controls the injection pulse width, and the electronically controlled carburetor controls the duty ratio of the electromagnetic valve that opens and closes the air bleed at a high frequency.

If we consider combustion with a lean mixture that deviates significantly from the stoichiometric air-fuel ratio, combustion in this lean mixture range is inherently prone to misfires, and for this reason,
For the purpose of stabilizing lean combustion, long discharge plasma ignition means (not shown) and gas flow control means are provided.

In other words, the long discharge plasma ignition means aims to ensure reliable ignition, shorten the subsequent initial combustion time, and suppress combustion fluctuations, and the gas flow control means aims to shorten the combustion time and expand the engine stability limit. be.

Therefore, the combustion characteristics of the lean burn engine will be specifically explained first based on FIG. 11.

The influence of gas flow on engine stability is large in the lean air-fuel ratio region, and compared to when the gas flow is weak (shown by the broken line), when the gas flow is moderately strengthened, the effect on the lean air-fuel ratio side (as shown by the solid line) stability limit expands in the direction).

However, if the gas flow is excessively increased (indicated by the dashed line), flame propagation during combustion will be extinguished, which will instead cause combustion fluctuations and lower the stability limit.

For this reason, appropriate gas flow strength is required.

In addition, in order to keep NOx emissions below the regulatory level without a catalyst, the air-fuel ratio must be leaner than A/F ₁ .

As a result, W between A/F ₁ and A/F ₂ becomes a lean air-fuel ratio range in which NOx emissions can meet the regulation value without installing a three-way catalyst, etc., and can improve fuel efficiency. It is only necessary to control the air-fuel ratio so that it falls within W.

Therefore, in actual control, the median value of W A/F ₀
is set as the set air-fuel ratio (the basic injection amount calculation means 25 calculates the basic injection amount so that the set air-fuel ratio A/F ₀ is achieved according to the operating conditions), and the air-fuel ratio correction means to be described later sets this A/F 0. Feedback control is performed so that the actual air-fuel ratio is kept within a small width εA/F (εA/F<W/2) with F ₀ as the center.

In this way, the lean air-fuel ratio range to be subjected to feedback control has been determined, so next it is necessary to detect the actual air-fuel ratio.

Therefore, in the present invention, among the parameters in the combustion chamber that directly affect NOx emissions and fuel efficiency,
Adopting parameters that are closely related to the air-fuel ratio,
The air-fuel ratio will be detected.

First, the relationship between the air-fuel ratio and the discharge characteristics is shown in FIG. 6.

In the same figure, the dielectric breakdown voltage V _B (see Figure 5)
is the stoichiometric air-fuel ratio A/F with respect to the change in the air-fuel ratio A/F.
Although it does not change much near Fth, it changes rapidly in a lean air-fuel ratio range far outside A/Fth, so in this range, A/F can be determined with high accuracy by detecting V _B.

Furthermore, according to Patsien's law, V _B strongly depends on the combustion chamber pressure (pressure between the spark plug electrodes) pig at the time of ignition (see Figure 7), so A/F is given as a function of V _B and pig. , V _B and pig are determined, A/F
is confirmed.

On the other hand, the strength of the gas flow is W
Since the limit value on the lean side (FIG. 11) is given, it is necessary to set the gas flow strength (flow velocity of gas flow) U and maintain an appropriate value U.

Therefore, the relationship between U and discharge characteristics is shown in Figure 8.
It will look like Figure 9.

When the discharge resistance R _S is held constant, as U increases as shown in Figure 8, the discharge time D _S becomes shorter, and when the discharge time D _S is held constant, as U increases as shown in Figure 9, the discharge resistance decreases. increase Figures 8 and 9 show the characteristics when either R _S or D _S is constant, but if the characteristics in Figure 9 are incorporated into Figure 8, R _S in Figure 8 is The bigger the D _S
The curve moves upward, and conversely, if R _S is small,
The D _S curve will move downward. In other words,
U is not uniquely determined when D _S (or R _S ) is determined, but U is determined only when Rs is determined in addition to D _S (U is a function of both D _S and R _S ).

Note that R _S is an average of the discharge resistance r _s that changes over time during one ignition.

As described above, in the present invention, four parameters V _B , pig, R _S , D _S are used for air-fuel ratio feedback control.
.

Therefore, referring back to FIG. 2, other components will be explained.

In order to obtain the four parameters, cylinder pressure detection means 20, peak voltage discrimination means 21, discharge resistance calculation means 22, and discharge time discrimination means 23 are provided.

Incidentally, the ignition voltage detection means 18 and the ignition current detection means 19 detect the ignition voltage v _s and the ignition current i _s (see FIG. 5 for both) supplied from the long discharge plasma ignition means.
This is to detect each.

Starting with the combustion chamber pressure detecting means 20 at the time of ignition, first, the combustion chamber pressure detecting means 20 at the time of ignition is
Detect pig.

The peak voltage determining means 21 determines _VB , which is the peak value of _Vs that changes with time.

The discharge resistance calculation means 22 _{calculates r S (} =v _{S /}
i _S ) and calculate the average discharge resistance R _S from this r _S.

The discharge time determining means 23 determines D _S from the change in i _s .

Next, a description will be given of the fuel supply amount correction means for feedback-correcting the actual air-fuel ratio to the A/F ₀ based on pig and _VB . It is composed of a change amount calculation means 36, a comparison means 38, a correction coefficient calculation means 39, and a correction calculation means 40.

That is, the air-fuel ratio calculating means 34 calculates the actual air-fuel ratio A/F based on the pig detected by the cylinder pressure detecting means 20 and the V _B detected by the peak voltage determining means 21.

In the air-fuel ratio change calculation means 36, this A/F
The difference ΔA/F (=A/F ₀ −A/F) between the reference value A/F ₀ and the reference value A/F 0 preset by the reference value setting means 35 is calculated.

The comparison means 38 compares |ΔA/F| with a reference value εA/F set in advance by the reference value setting means 37.

In this case, |△A/F| represents the actual deviation from the set air-fuel ratio A/F ₀ , and εA/F represents the allowable range of deviation, so |△A/F| falls within εA/F. There is no problem if |△A/F| is εA/
If it is outside F, |ΔA/F| needs to be within εA/F.

Therefore, in the case of |ΔA/F|>εA/F, the correction coefficient calculation means 39 calculates the correction coefficient α (=ΔA/F) corresponding to ΔA/F.

The correction calculating means 40 corrects the basic injection amount Tp using this α as a feedback correction coefficient.

For example, if the air-fuel ratio exceeds εA/F and deviates to the lean air-fuel ratio side, Tp is corrected to increase, and if it exceeds εA/F and deviates to the stoichiometric air-fuel ratio side, Tp is corrected to decrease.

In this way, the fuel supply amount correction means performs feedback control of the air-fuel ratio.

Next, gas flow correction means for maintaining the gas flow strength at an appropriate level will be explained. In this case, the control by the gas flow correction means is similar to the control by the fuel supply correction means described above in the sense that the strength of the gas flow is maintained at the set value based on the actual detected value.

That is, the gas flow correction means is composed of a gas flow rate change calculation means 29, reference value setting means 28, 30, comparison means 31, drive pulse width calculation means 32, and drive means 33.

Starting from the gas flow calculation means 27, the gas flow calculation means 27 calculates the actual U based on R _S calculated by the discharge resistance calculation means 22 and D _S determined by the discharge time determination means 23. .

The gas flow change amount calculation means 29 calculates this U and the reference value U _O set in advance by the reference value setting means 28.
Calculate the difference ΔU (=U _O - U) between the two. Comparison method 3
In step 1, |ΔU| is compared with a reference value ε _U set in advance by the reference value setting means 30.

In this case, |△U| represents the actual deviation from the set flow velocity U _O , and ε _U represents the allowable range of deviation, so
There is no problem if |△U| is within ε _U , but if |△U| is outside ε _U , it is necessary to make |△U| fall within ε _U.

Therefore, in the case of |△U|>ε _U , the drive pulse width calculation means 32 calculates the drive pulse width T corresponding to △U.
(=ΔU), and based on this T, the driving means 33 drives the actuator of the gas flow means 17.

For example, the gas flow means 17 is provided with a sub-intake port of a small cross-sectional area that branches from the main intake port and merges again near the intake valve, with respect to the main intake port located downstream of the intake throttle valve; A second throttle valve separate from the intake throttle valve is installed in the main intake port, and as the second throttle valve is closed, the amount of gas flowing to the sub-intake port increases, and the flow rate of the gas flow increases. There are some things that I do.

In this case, if |△U| exceeds ε _{U and} the flow velocity is high, the flow velocity can be increased by increasing the valve opening of the second throttle valve and reducing the amount of gas flowing to the sub-intake port. If |ΔU| exceeds ε _U and the flow velocity is slowing down, the opening degree of the second throttle valve is conversely decreased to increase the flow velocity.

In this way, the gas flow correction means maintains the gas flow strength at the set value.

Therefore, the set air-fuel ratio is directly feedback-controlled by the parameters obtained in the combustion chamber, which further improves acceleration response, improves fuel efficiency, and maintains exhaust emissions within the limits of engine stability. This makes it possible to realize a lean burn engine that satisfies the following requirements at the same time.

(Embodiment) FIG. 3 is a schematic diagram of an embodiment of the present invention.

First, to explain the long discharge plasma ignition device, the long discharge plasma ignition device has a primary winding 5
2, an ignition coil 51 having a secondary winding 53, a power transistor 54, a distributor 55, plasma ignition plugs 56a to 56d, and a DC-DC converter 57.

That is, when the ignition coil primary current is cut off based on the ignition signal _S1 from the means for instructing the ignition timing in synchronization with the engine rotation, a high voltage is induced on the secondary side of the ignition coil 51, and this high voltage is supplied to plasma ignition plugs 56a-56d.

The plasma ignition plugs 56a to 56d generate a high-temperature, high-energy thermal plasma flow in the discharge gap,
Ignite the fuel.

Further, the DC-DC converter 57 has a dielectric breakdown voltage after the spark discharge from the ignition plug occurs.
This DC-DC converter 57 is provided to take advantage of the fact that the discharge action is sustained at a voltage lower than V _B , and this DC-DC converter 57 superimposes a high voltage sufficient to sustain the discharge action on the high voltage generated by the primary current interruption. ignition current i _s and ignition voltage v _s in FIG. 5).

Therefore, the long discharge plasma ignition device aims to ensure reliable ignition in lean combustion, shorten the subsequent initial combustion time, and suppress combustion fluctuations.

Note that V _BAT is the battery voltage, and V ₁ and V ₂ are reference voltages generated from V _BAT .

Next, the peak voltage discriminator 60 is composed of a resistor 61, buffer amplifiers 62 and 66, an inverting amplifier 63, a peak hold circuit 64, a sample hold circuit 65, etc., and detects the peak of the ignition voltage v _s flowing to the secondary side of the ignition coil 51. It holds the value (breakdown voltage) and outputs the peak voltage V _B '.

Note that since the actual dielectric breakdown voltage V _B is a high voltage on the order of kV, the voltage is dropped to the order of V through the high resistance 61, and V _B ′=C・V _B
There is a relationship (C; constant, C<<1) (see Figure 5).

The discharge time discriminator 70 includes a comparator 71, an inversion circuit 73, and mono multivibrators 72 and 74.
The discharge time D _S at the time of one ignition is determined (see Fig. 5).

That is, the period from when the mono multivibrator 72 starts up to when the mono multivibrator 74 starts up becomes D _S.

The discharge resistance calculation circuit 80 includes a buffer amplifier 8
1, 82, A/D converter 83, 84, division circuit 8
Consists of 5.

That is, the discharge voltage v _s ′ (=C・v _s ), the discharge current
i _s is converted into a digital value via A/D converters 83 and 84, and from the converted value, the discharge resistance r _s ′ (=v _s ′/i _s ) is calculated by the dividing circuit 85. The calculation result is output to the control unit 90 as a digital value.

On the other hand, the in-cylinder pressure sensor 42 is formed, for example, in the shape of a spark plug washer, and this sensor 42 is attached to the combustion chamber wall together with the spark plug, and the sensor output is subjected to signal processing using a known method.
The combustion chamber pressure PIG at the time of ignition can be extracted as a signal. For example, the cylinder pressure P and the crank angle position θ at that time are sampled as a couple (P, θ), and the ignition timing instruction value at that time is
Find θ that matches ADV, and set the in-cylinder pressure P that is coupled with that θ as pig.

Further, the intake negative pressure sensor 43 detects the intake pipe internal negative pressure p corresponding to the engine load, and the rotation sensor 44 detects the engine rotation speed N.

Since the detected values of these sensors 42 to 44 are analog values, they are converted into digital values by A/D converters 45 to 47 and then output to the control unit 90.

Note that an air flow meter that detects the amount of intake air may be used instead of the intake negative pressure sensor 43, and a crank angle sensor may be used instead of the rotation sensor 44. Note that if the crank angle 1° signal output from the crank angle sensor is used, an A/D converter is not necessary since it is already a digital value.

In this way, V _B ′, D _S , r _s ′pig obtained by the peak voltage discriminator 60, discharge time discriminator 70, discharge resistance calculation circuit 80, cylinder pressure sensor 42, suction negative pressure sensor 43, and rotation sensor 44, respectively. , p, and N, the control unit 90 controls the fuel supply system 94 and the gas flow system 100.

In this case, the fuel supply device 94 includes, for example, a fuel injection device or an electronically controlled carburetor, and in the case of a fuel injection device, adjusts the opening period of the fuel injection valve (corresponding to the fuel injection amount). By doing so, the air-fuel ratio is controlled.

Further, the gas flow device 100 will be further explained based on FIG. 4.

In the figure, the intake passage 1 downstream of the intake throttle valve 102
01 branched from the main intake port 105 to the intake valve 10
A sub-intake port 106 with a small cross-sectional area that joins the main intake port 105 again near No. 3 is defined. There is.

Note that the sub intake port 106 is connected to the second throttle valve 107.
The combustion chamber 104 is arranged so that the gas flow flowing into the combustion chamber 104 generates a swirl in the combustion chamber 104 when the valve is closed.
It is open towards.

Therefore, the flow velocity U of the gas flow generated in the combustion chamber 104 changes depending on the opening degree of the second throttle valve 107. For example, if U is to be made small, the opening degree of the second throttle valve 107 The opening degree may be increased to allow more gas to flow through the main intake port 105.

This second throttle valve 107 is operated by an actuator (servo motor) 109 connected via a link rod 108. The servo motor 109 is, for example, a step motor that follows the rotation angle in synchronization with the input pulse frequency. Configure.

Therefore, the control unit 90 controls the second pulse frequency by adjusting this input pulse frequency.
U is controlled via the opening degree of the throttle valve 107.

Returning to FIG. 3, the control unit 90 will be explained.
is a microcomputer that performs digital control, and mainly includes an input/output signal processing circuit (I/O) 91, a central processing unit (CPU) 92, and a storage device (ROM) 9.
3, and the detection signals are all I/O
91 as a digital signal.

Note that the output signal of the peak voltage discriminator 60 is also converted into a digital signal.

Next, the operation of the above configuration will be explained based on the flowchart of FIG. 10.

The basic injection amount Tp of fuel that provides an air-fuel ratio leaner than the stoichiometric air-fuel ratio is stored in the ROM 93 in advance with respect to the suction negative pressure p and the engine speed N, and the detected p and N are used as grid axes. Tp is determined by looking up the three-dimensional table (P ₁ −P ₂ ).

In this case, if the fuel supply device 94 limits the amount of fuel supplied by the fuel injection valve of the fuel injection device, this Tp may be set to give the opening period of the fuel injection valve, and this Tp may be set as a pulse. When a signal indicating the width is output to the fuel injection valve, fuel is supplied during this period, and an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio is formed.

Actually, this Tp is further corrected by the fuel temperature, water temperature, etc., _{and Te} is output as the drive pulse width ( _P16 - _P17 ).

Note that Te is given by Te=Tp (1+α+γ), where α indicates a feedback correction coefficient (described later), and γ collectively indicates correction coefficients based on fuel temperature, water temperature, etc.

Next, feedback control of the air-fuel ratio will be explained. In this control calculation, α is determined by comparing the actually detected air-fuel ratio with a preset air-fuel ratio.

To be more specific, the reference value A/F ₀ of the lean air-fuel ratio and _the allowable range εA/F (Fig. (see P ₁ , P ₃ ).

On the other hand, it is necessary to calculate the actual air-fuel ratio A/F to be compared with this reference value A/F ₀ .

Therefore, since A/F is given by the function f of pig and V _B as mentioned above, A/F=f(pig,
V _B ) may be used to calculate A/F (or table pickup), but in this control, pig,
For V _B , adopt the specific time and average value ig, _B. That is, ig = (1/m) _n 〓 pig, _B =
(1/m) _n 〓 V _B (where V _B ′=C·V _B ) is calculated (P ₆ , P ₇ ).

Note that m is a positive integer, mx (control calculation period)
is set as a specific time.

Therefore, A/F is given as a function f of ig and _B , and A/F is determined by a three-dimensional table search with ig and _B as lattice axes (P ₁₀ ).

Next, in order to see whether the deviation between A/F and A/F ₀ is within εA/F, the reference value A/F _{0 is}
Deviation of air-fuel ratio from △A/F (=A/F ₀ −A/
The absolute value of F) |ΔA/F| is compared with εA/F (P ₁₂ to _{P 14} ).

If |△A/F| is within εA/F,
Although there is no need for correction (P ₁₄ −P ₂₁ ), if |△A/F| exceeds εA/F, the correction coefficient α is changed to α=△A/ Calculate as F (P ₁₄ −P ₁₅ ).

For example, if A/F deviates from εA/F and shifts to the lean side (rightward in Figure 11), α(=△A/
F)>0, Tp is corrected to increase, and the air-fuel ratio moves toward the stoichiometric air-fuel ratio A/Fth again.

Similarly, if A/F deviates to the A/Fth side, α
<0, Tp is corrected to decrease, and the air-fuel ratio moves to the lean side.

In this way, the air-fuel ratio is corrected and controlled within the allowable range εA/F.

On the other hand, regarding the flow rate U of gas flow, U is D _S
As mentioned above, it is given as a function of R _S ,
For D _S and R _S , the average values _S and _S of a specific time are adopted, and U is read out by a three-dimensional table search with _S and _S as the lattice axes, and this read value U is stored in the ROM 93 in advance. Compare with reference value U _O of the gas flow velocity (P ₁ , P ₃ ~ _{P 5} , P ₈ ,
_P9 , _P11 ).

In this case, the average discharge resistance per ignition R _S
is R _S = (1/n) _o 〓 (v _s /i _s ) (where, v _s ′=C・
v _s , n is a positive integer), and _S further averages this R _S over a specific time. ( _RS = (1/
m) _n 〓 R _S ). Note that the allowable width εU from U _O is also read out at the same time.

Therefore, if |△U| exceeds ε _U and deviates from it, for example, if the flow velocity deviates from ε _U and is small, △U>0, and the corrected drive pulse width T is calculated from this △U (T=△U ), and a drive signal generated from this T is output to the step motor (P ₁₈ to _{P 20} ).

In this case, when T(=△U)>0, the second throttle valve 1
07 is made smaller, the gas flow rate to the auxiliary intake port 106 increases, and the combustion chamber 1
Increase the flow rate in 04.

When T<0, the flow velocity is reduced, contrary to the above-mentioned operation, and the flow velocity eventually falls within the control range.

Note that if |△U| falls within ε _U , the step motor 109 is not operated (P ₁₈ −P ₂₂ ).

As a result, a moderate gas flow rate is maintained and the engine stability limits are expanded and maintained.

The air-fuel ratio is then precisely feedback-controlled in the lean air-fuel ratio region that is formed between this expanded stability limit and the position where the NOx emission regulation value is cleared without the need for a catalyst. (See Figure 11).

(Effects of the Invention) As described above, according to the present invention, parameters closely related to the air-fuel ratio obtained in the combustion chamber are directly adopted as parameters for performing correction control, so responsiveness is significantly improved. It shows its true potential, especially when accelerating.

In addition, the lean air-fuel ratio correction control of the second invention, in which a means for maintaining appropriate gas flow is added, simultaneously achieves the best fuel efficiency, clears the NOx emission regulation value, and maintains engine stability. This means that a combustion engine can be realized.

Furthermore, by detecting the parameters in the combustion chamber for each cylinder, the air-fuel ratio can be controlled by adding parameters between the cylinders (however, in this case, both the fuel supply system and the gas flow system can be used for each cylinder. (A type that can operate independently in each cylinder) enables air-fuel ratio feedback control for each cylinder, making it possible to realize a lean burn engine of even higher quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventional device. FIG. 2 is an overall configuration diagram for clearly showing the configuration of the present invention. FIG. 3 is a schematic configuration diagram of an embodiment of the present invention, and FIG. 4 is a longitudinal sectional view of the gas flow device. FIG. 5 is an explanatory diagram showing the spark discharge characteristics and the output characteristics of the peak voltage discriminator and the ignition time discriminator. FIG. 6 is a diagram showing the relationship between dielectric breakdown voltage and air-fuel ratio, and FIG. 7 is a diagram showing the relationship between ignition pressure and dielectric breakdown voltage. FIG. 8 and FIG. 9 are diagrams showing the discharge time and discharge resistance with respect to the gas flow velocity, respectively. 1st
FIG. 0 is a flowchart of what is carried out within the control unit of FIG. FIG. 11 is an explanatory diagram showing engine stability, NOx emissions, and fuel efficiency in a lean air-fuel ratio region. 11...Rotational speed detection means, 12...Load detection means, 16...Fuel supply means, 17...Gas flow means, 18...Ignition voltage detection means, 19...Ignition current detection means, 21...Peak voltage Discrimination means, 22
...Discharge resistance calculating means, 23...Discharge time determining means, 25...Basic injection amount calculating means, 26...Drive means, 27...Gas flow calculating means, 28, 30...
. . . Reference value setting means, 29 . . . Gas flow change amount calculation means, 31 . . . Comparison means, 32 . Reference value setting means, 36...
...Air-fuel ratio change calculation means, 38...Comparison means, 3
9... Correction coefficient calculating means, 40... Correction calculating means, 42... Cylinder pressure sensor, 43... Intake negative pressure sensor, 44... Rotation sensor, 51... Ignition coil, 54... Power transistor, 56a~ 56d
...Plasma ignition plug, 57...DC-DC converter, 60...Peak voltage discriminator, 70...Discharge time discriminator, 80...Discharge resistance calculation circuit, 90...
Control unit, 94...Fuel supply system,
100... Gas flow device, 101... Intake passage,
102...Intake throttle valve, 103...Intake valve, 104
...Combustion chamber, 105...Main intake port, 106...
...Sub-intake port, 107...Second throttle valve, 109...
…Servomotor.

Claims (1)

[Scope of Claims] 1. A combustion engine comprising: an ignition means attached to the combustion chamber; and a fuel supply control means for controlling the amount of fuel supplied so as to obtain a predetermined lean air-fuel ratio based on a detected value of the operating state of the engine. In an internal combustion engine, means for detecting dielectric breakdown voltage due to ignition means, means for detecting combustion chamber pressure at the time of ignition for detecting combustion chamber pressure at the time of ignition, and calculating the air-fuel ratio of combustion gas based on the detection results of both means. 1. An air-fuel ratio control device for an internal combustion engine, comprising: an air-fuel ratio calculating means for calculating the calculated air-fuel ratio; and a fuel supply amount correcting means for feedback-controlling the fuel supply amount based on the calculated air-fuel ratio. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the ignition means is a plasma long discharge ignition means. 3. In an internal combustion engine equipped with an ignition means attached to a combustion chamber and a fuel supply control means for controlling the amount of fuel supplied so as to obtain a predetermined lean air-fuel ratio based on a detected value of the operating state of the engine, the ignition means means for detecting the dielectric breakdown voltage caused by the ignition; combustion chamber pressure detection means at the time of ignition for detecting the combustion chamber pressure at the time of ignition; and air-fuel ratio calculation means for calculating the air-fuel ratio of the combustion gas based on the detection results of both of these means. , a fuel supply amount correcting means for feedback-controlling the fuel supply amount based on the calculated air-fuel ratio, a gas flow means for variably generating in-cylinder gas flow, and detecting the discharge time and discharge resistance of the ignition means. gas flow calculation means for calculating the strength of the gas flow based on the detection results of both of these means; and gas flow correction means for feedback controlling the gas flow means so that the calculated value becomes a set value. An air-fuel ratio control device for an internal combustion engine, characterized in that it is provided with: