JP3428611B2 - Combustion fluctuation control device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion fluctuation control device for an internal combustion engine mounted on an automobile, etc. The present invention relates to a control device that controls combustion fluctuations caused by.

[0002]

[Related technical field] Air-fuel ratio of air-fuel mixture supplied to an internal combustion engine in order to reduce harmful gas components emitted from a fuel injection spark ignition type internal combustion engine mounted in an automobile or to improve fuel efficiency of the engine. A lean combustion method has been proposed in which is set to a fuel lean side (lean side) significantly from the stoichiometric air-fuel ratio, and a combustion method in which a large amount of exhaust gas is recirculated in addition to lean combustion is proposed. Since lean combustion makes it difficult to reduce NOx by a conventional three-way catalyst, NOx is reduced by exhaust gas recirculation (EGR).

As an engine that realizes this combustion method, an air bypass valve (ABV valve) is provided in a bypass passage that bypasses the throttle valve, and a large amount of bypass intake air amount can be adjusted by this ABV valve. Further, an exhaust gas recirculation valve (EGR valve) is provided in an exhaust gas recirculation passage that connects the exhaust system and the intake system, the exhaust gas recirculation amount is adjusted by this EGR valve, and a fuel injection valve is provided in each intake port of each cylinder. The fuel is injected from the fuel injection valve into the intake air in the intake passage, and the air-fuel mixture generated in the intake passage is supplied to the combustion chamber. Then, a strong and stable vortex flow is generated by the air-fuel mixture sucked into the combustion chamber to enable lean combustion.

Various engines (hereinafter referred to as in-cylinder injection gasoline engines) which employ in-cylinder injection type in which fuel is directly injected into a combustion chamber in place of the conventional intake passage injection type have been proposed. An in-cylinder injection gasoline engine, for example, locally produces an air-fuel mixture having an air-fuel ratio close to the stoichiometric air-fuel ratio in the periphery of a spark plug or in a cavity provided in a piston, so that the air-fuel ratio is lean as a whole. However, it has the advantage that ignition is possible, CO and HC emissions are reduced, and fuel efficiency during idle operation and steady running can be greatly improved. Further, the in-cylinder injection gasoline engine has an advantage that the acceleration / deceleration response is also very good because there is no transfer delay due to the intake pipe when the fuel injection amount is increased or decreased. However, when the load is high, the fuel injection amount increases and the vicinity of the spark plug becomes rich in fuel (rich). When the overall air-fuel ratio (also referred to as the average air-fuel ratio) approaches the stoichiometric air-fuel ratio side, so-called rich misfire occurs, It has the drawback of having a small area for stable operation. This is because it is difficult to change the injection amount per unit time of the fuel injection valve and the injection direction, so it is difficult to maintain the local air-fuel ratio near the spark plug at an optimum value over the entire engine operating range. And so on.

In order to solve such a drawback, fuel injection is performed at an appropriate timing according to the load, and the shape of the combustion chamber is designed according to this, for example,
It is proposed in JP-A-5-79370. More specifically, there has been proposed a method of switching between a late injection mode in which fuel is injected during the compression stroke and an early injection mode in which fuel is injected during the intake stroke, depending on the load. This conventional proposed in-cylinder injection gasoline engine injects fuel into the cavity at the end of the compression stroke during low-medium load operation, and locally mixes around the spark plug and in the cavity with an air-fuel ratio close to the theoretical air-fuel ratio. To form. As a result, ignition is possible even with a lean air-fuel ratio as a whole, CO and HC emissions are reduced, and fuel efficiency during idle operation and steady running is significantly improved. Further, during high load operation, fuel is injected outside the cavity during the intake stroke to form an air-fuel mixture with a uniform air-fuel ratio in the combustion chamber. This makes it possible to burn an amount of fuel equivalent to that of the intake pipe injection type, and secure the output required at the time of starting and accelerating.

Whether the above-mentioned intake passage injection type engine or in-cylinder injection gasoline engine, if lean combustion is performed, there is almost no NOx purification effect by the three-way catalyst, and a large amount of EGR is indispensable for reduction of NOx. Is known to be. When such a large amount of EGR is performed, the operation is performed near the combustion limit, so precise control of the EGR amount is necessary, and the EGR valve is opened and closed by a stepper motor that can precisely control the valve opening degree. The type used is used.

[0007]

FIG. 1 shows the valve opening of the EGR valve (the number of steps of the stepper motor) and the in-cylinder pressure when the in-cylinder injection gasoline engine is in the normal idling operation in the latter injection mode (the latter lean mode). (Pi) shows the relationship with the fluctuation rate (%), and thus shows the relationship between the EGR amount and the Pi fluctuation rate. At a certain operating point in the low load operation region, the amount of fuel that secures the required output is determined, and in order to obtain the required exhaust gas characteristics, the throttle valve and A
The fresh air amount to be supplied via the BV valve and the EGR amount to be supplied via the EGR valve are determined, and the basic EGR position (Pbs) in FIG. 1 is obtained. And this basic EGR
When the EGR amount is increased with respect to the position, better exhaust gas characteristics and fuel economy are obtained, but the Pi fluctuation rate gradually increases, and the fluctuation limit (Pma
Above x), the frequency of misfires increases and the rate of change of the Pi fluctuation rate (gradient of the graph) also increases. Further EGR
When the amount is increased, the fluctuation rate of Pi finally increases (at the Pupl point), and the engine stalls.

As described above, even in the vicinity of the fluctuation limit, even a slight increase in the EGR amount may lead to misfire. If there are variations in the characteristics of the EGR valve, offset (step out) of the set position of the stepper motor, etc.
Due to these factors, the EGR amount cannot be adjusted to an appropriate amount, which may cause misfire and engine stall.
Even if the supplied EGR amount is correct according to the control program, misfire may occur due to environmental conditions such as atmospheric temperature and humidity.

In order to eliminate such an inconvenience, conventionally, the combustion fluctuation of the engine is detected and E is changed according to the combustion fluctuation amount.
Techniques for preventing the engine stall by adjusting the GR amount or the air-fuel ratio have been proposed by Japanese Patent Laid-Open No. 182516/1983 and Japanese Utility Model Publication No. 3-030601. Also,
Japanese Patent Application Laid-Open No. 5-263718 proposes a technique for detecting an EGR abnormality based on the combustion state of the engine (for example, the cylinder pressure variation rate).

However, during the latter lean mode operation of the lean-burn engine, particularly the cylinder injection engine, the local air-fuel ratio is set so as to stabilize the combustion in the cylinder, and therefore the above-mentioned known technique is applied. Unlike the engine described above, it can be operated even in an extremely lean state with an overall air-fuel ratio of about 40. Therefore, in such an engine, stable combustion is possible even if the EGR amount is extremely increased as compared with a normal engine, while in the vicinity of the fluctuation limit shown in FIG. 1, even a slight change in the EGR amount causes Pi fluctuation. It will greatly affect the rate. In other words, in the lean combustion engine such as the in-cylinder injection engine described above, the influence of the EGR amount is large in the vicinity of the fluctuation limit with respect to the combustion fluctuation,
In the region lower than the fluctuation limit, adjusting the air-fuel ratio can stabilize the operation of the engine more effectively than adjusting the EGR amount.

Further, when the exhaust gas recirculation device malfunctions such that the EGR valve is stuck due to soot or the like and does not operate, no matter how much the EGR amount is adjusted according to the combustion fluctuation,
Since it is not possible to adjust it, there is a possibility that it will not be possible to deal with the deterioration of drivability due to an increase in NOx emissions, combustion instability, and engine stall. There is a need.

The present invention has been made in view of the above problems, and effectively prevents misfires and engine stalls by combining EGR amount adjustment and air-fuel ratio adjustment with respect to engine combustion fluctuations. An object of the present invention is to provide a combustion fluctuation control device for an internal combustion engine that prevents deterioration of drivability and deterioration of exhaust gas characteristics.

[0013]

Therefore SUMMARY OF THE INVENTION, the combustion change control system for an internal combustion engine according to claim 1, the combustion variation detecting means for detecting the combustion fluctuation of the internal combustion engine, calculates the evaluation parameter values relating to the combustion variation, Judgment means for judging combustion deterioration when the evaluation parameter value is a predetermined value or more,
An exhaust gas recirculation device for controlling the recirculation amount of exhaust gas recirculated from the exhaust system to the intake system, and an exhaust gas recirculation amount correction means for reducing the exhaust gas recirculation amount to a predetermined reduction value when the deterioration of combustion is determined by the determination means. When, and a fuel ratio changing means for changing the target air-fuel ratio to a predetermined enrichment value of the fuel-rich side from the reduction of the exhaust gas recirculation amount according to the exhaust gas recirculation amount compensation means is started after a predetermined period of time, Exhaust gas return
The flow rate correction means determines whether the combustion has deteriorated by the determination means.
The exhaust gas recirculation amount is reduced below the specified reduction value
Change to a small amount of intermediate decrease value and change to the intermediate decrease value.
Is the reduction rate of the exhaust gas recirculation amount until it reaches the intermediate reduction value?
From the reduction rate of exhaust gas recirculation amount from the above to the above-mentioned predetermined reduction value
It is characterized by being different .

According to the first aspect of the present invention, the EGR amount, which has a great influence on the deterioration of combustion, is first reduced, and the deterioration of combustion is promptly reduced while the exhaust gas components, particularly NOx, are not deteriorated.
Yes. On the other hand, by delaying the air-fuel ratio by delaying for a predetermined period, the combustion fluctuation is reliably suppressed even if the combustion fluctuation cannot be eliminated only by EGR. In the control device according to the second aspect, the predetermined decrease value is set to a value at which a specific exhaust gas component in exhaust gas, for example, NOx, does not deteriorate more than a predetermined amount. It is difficult to reduce the combustion variation without deteriorating the exhaust gas component by a predetermined amount by controlling the combustion variation with the EGR amount alone, but this is made possible by changing the target air-fuel ratio to a predetermined enrichment value.

In the control device according to the third aspect, the predetermined enrichment value is set to a value at which the fuel consumption does not deteriorate more than a predetermined value, and the combustion fluctuation is reduced without deteriorating the fuel consumption more than the predetermined value. In the control device according to the fourth aspect, the predetermined decrease value is set to a value at which the exhaust gas recirculation device is fully closed. That enables the reduction of rapid combustion fluctuation.

[0016]

According to a fifth aspect of the present invention, a deviation between the evaluation parameter value obtained by the combustion fluctuation detecting means and the predetermined value is obtained, and when the deviation exceeds a determination threshold value, the exhaust gas recirculation amount correcting means is provided. Is characterized in that the exhaust gas recirculation amount is reduced to the intermediate reduction value. When the combustion fluctuation is large, the EGR amount is promptly reduced. According to a sixth aspect of the present invention, the intermediate decrease value is corrected according to the magnitude of the deviation. By setting the intermediate decrease value according to the combustion fluctuation, it is possible to prevent the EGR amount from being excessively decreased and prevent the exhaust gas performance from being significantly deteriorated.

A control device according to a seventh aspect is characterized in that the exhaust gas recirculation amount is reduced to the intermediate reduction value and then gradually reduced to the predetermined reduction value. It is possible to prevent the exhaust gas performance from being significantly deteriorated due to the excessive decrease of the EGR amount. Claim
In the control device according to the eighth aspect , the predetermined period is a period from when the reduction of the exhaust gas recirculation amount is started to when the exhaust gas recirculation amount reaches the predetermined reduction value. EGR
After the control of is completely completed and the EGR amount is stabilized, the target air-fuel ratio enrichment control is performed, and the air-fuel ratio is prevented from varying due to the influence of EGR.

According to a ninth aspect of the present invention, the air-fuel ratio changing means sets the evaluation parameter value obtained by the combustion fluctuation detecting means to the second predetermined value after a predetermined period has elapsed since the reduction of the exhaust gas recirculation amount was started. When the value exceeds the value, the target air-fuel ratio is changed to a predetermined enrichment value on the fuel rich side. E
Even when it is difficult to reduce the combustion fluctuation only by the GR reduction control, the combustion fluctuation is suppressed by the air-fuel ratio enrichment control.

According to a tenth aspect of the present invention, the air-fuel ratio changing means gradually changes the target air-fuel ratio to the predetermined enrichment value. Reduces combustion fluctuations without degrading fuel efficiency. In the control apparatus according to claim 11 , the air-fuel ratio changing means changes the target air-fuel ratio to the predetermined enrichment value. Therefore, the combustion fluctuation is promptly suppressed.

According to a twelfth aspect of the present invention, the air-fuel ratio changing means temporarily changes the target air-fuel ratio to an intermediate enrichment value on the fuel lean side of the predetermined enrichment value.
Therefore, the fuel efficiency is not deteriorated by temporarily changing the target air-fuel ratio to the intermediate enrichment value at once to quickly reduce the combustion fluctuation, and temporarily holding the target air-fuel ratio at the intermediate enrichment value. Claim 13
In the control device described above, the air-fuel ratio changing means obtains a second deviation between the second predetermined value and the evaluation parameter value obtained by the combustion variation detecting means after the predetermined period has elapsed, and the second deviation is the second deviation. The target air-fuel ratio is changed to the intermediate enrichment value when the determination threshold is exceeded. Therefore, only when it is determined that the combustion variation is large based on the second deviation, the target air-fuel ratio is quickly enriched.

According to a fourteenth aspect of the present invention, the intermediate concentration value is corrected according to the magnitude of the second deviation. The intermediate enrichment value is set in accordance with the magnitude of the combustion fluctuation, and it is possible to prevent the target air-fuel ratio from being excessively enriched, and thus to avoid a significant deterioration in fuel consumption. According to a fifteenth aspect of the present invention, the target air-fuel ratio is changed to the intermediate enrichment value and then gradually changed to the predetermined enrichment value. It is possible to prevent the fuel efficiency from being significantly deteriorated due to the excessive enrichment of the target air-fuel ratio.

According to a sixteenth aspect of the present invention, there is provided failure determination means for determining that the exhaust gas recirculation device is out of order if the evaluation parameter exceeds the predetermined value even after the predetermined period has elapsed. It is characterized by being prepared.
Combustion fluctuations are reduced while making a failure determination of the EGR device. 18. The exhaust gas recirculation device according to claim 17 , wherein the exhaust gas recirculation device is provided with an exhaust passage for recirculating exhaust gas from an exhaust system to an intake system, and an exhaust gas recirculation valve arranged in the middle of the exhaust passage for adjusting an exhaust gas recirculation amount. And an average value of the evaluation parameter values obtained by the combustion variation detecting means, and the valve opening reference position of the exhaust gas recirculation valve is corrected based on the average value. The valve opening reference position is corrected while detecting combustion fluctuations due to step-out of the motor that drives the exhaust gas recirculation valve, displacement of the valve body and position detection sensor, and the like.

The control device according to claim 18 is provided with a stop means for stopping the reduction of the exhaust gas recirculation amount by the exhaust gas recirculation amount correction means when the evaluation parameter value is equal to or less than the predetermined value. And Therefore, when the combustion fluctuation is eliminated, the EGR reduction control is stopped, so that unnecessary deterioration of exhaust gas performance and deterioration of fuel consumption are prevented.

A control device according to a nineteenth aspect of the present invention is characterized in that the control device comprises second stop means for stopping the change of the target air-fuel ratio by the air-fuel ratio changing means when the evaluation parameter value is equal to or less than the predetermined value. To do. Therefore, when the combustion fluctuation is eliminated, the air-fuel ratio enrichment control is stopped, so that unnecessary deterioration of exhaust gas performance and deterioration of fuel efficiency are prevented. The control device according to claim 20 , wherein the exhaust gas recirculation amount correction means increases the exhaust gas recirculation amount when the evaluation parameter value becomes equal to or less than a third predetermined value which is set to a value smaller than the predetermined value. It is characterized by When the combustion fluctuation is small while monitoring the combustion fluctuation, the exhaust gas performance and the fuel economy are improved.

[0026] In the control apparatus according to claim 21, wherein, when the evaluation parameter value is equal to or less than a fourth predetermined value set to the predetermined value smaller value, the air-fuel ratio changing means, the target air-fuel ratio lean fuel It is characterized by gradually changing to the value on the side. When the combustion fluctuation is small while monitoring the combustion fluctuation, the exhaust gas performance and the fuel economy are improved.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings by describing various embodiments in detail. (First Embodiment) FIG. 2 shows a first embodiment of the present invention, and is a schematic configuration diagram of an engine control system. FIG. 3 is a longitudinal sectional view of a cylinder injection gasoline engine according to the first embodiment.
In these figures, 1 is a cylinder injection type in-line 4 for automobiles.
It is a cylinder gasoline engine (hereinafter, simply referred to as an engine), and a combustion chamber, an intake device, an EGR device, and the like are designed only for in-cylinder injection.

In the case of the present embodiment, the cylinder head 2 of the engine 1 is provided with the spark plug 3 and the electromagnetic fuel injection valve 4 for each cylinder, and the fuel is directly injected into the combustion chamber 5. It is like this. A hemispherical cavity 8 is formed on the top surface of the piston 7 that slides in the cylinder 6 and reciprocates, at a position where the fuel spray from the fuel injection valve 4 reaches near the top dead center. (FIGS. 3 and 5).
The theoretical compression ratio of the engine 1 is set higher (about 12 in this embodiment) than that of the intake pipe injection type. A DOHC4 valve type is adopted as a valve mechanism, and intake and exhaust valves 9, 10 are provided on the upper part of the cylinder head 2.
An intake side camshaft 11 and an exhaust side camshaft 12 are rotatably held to drive each of the above.

Both camshafts 1 are attached to the cylinder head 2.
An intake port 13 is formed in a substantially upright direction so as to pass through between 1 and 12, and the intake flow passing through the intake port 13 generates a reverse tumble flow in the combustion chamber 5 described later. ing. On the other hand, the exhaust port 14 is formed in a substantially horizontal direction like a normal engine, but an EGR port 15 (not shown in FIG. 3) having a large diameter is obliquely branched. In the figure, 16 is a water temperature sensor that detects the cooling water temperature TW, and 17 is a crank angle sensor that outputs a crank angle signal SGT at a predetermined crank position of each cylinder (5 ° BTDC and 75 ° BTDC in this embodiment). And 19 is an ignition coil that outputs a high voltage to the ignition plug 3. A cylinder discriminating sensor (not shown) that outputs a cylinder discriminating signal SGC is attached to a camshaft or the like that rotates at a half speed of the crankshaft to discriminate which cylinder the crank angle signal SGT belongs to. .

As shown in FIG. 3, the intake port 13 is provided with an air cleaner 22, a throttle body 23, and a stepper motor type idle speed control valve (called an idle control valve) via an intake manifold 21 having a surge tank 20. ) 24 is connected to the intake pipe 25. Further, the intake pipe 25 is provided with a large-diameter air bypass pipe 26 that bypasses the throttle body 23 and introduces intake air into the intake manifold 21, and a linear solenoid type large-sized ABV is provided in the pipe line. A valve (air bypass valve) 27 is provided. In addition, the air bypass pipe 2
6 has a flow passage area corresponding to that of the intake pipe 25.
When the V valve 27 is fully opened, the required amount of intake air can be circulated in the low and medium speed range of the engine 1. On the other hand, the idle control valve 24 has a smaller flow passage area than the ABV valve 27, and the idle control valve 24 is used when adjusting the intake air amount with high accuracy.

In the throttle body 23, a butterfly type throttle valve 28 for opening and closing the flow path, a throttle sensor 29 for detecting the opening θTH of the throttle valve 28,
An idle switch 30 for detecting the fully closed state is provided. In the figure, 31 is a boost pressure (MAP: Manifold Absolute Pressure) sensor for detecting the intake pipe pressure Pb, which is connected to the surge tank 20.

On the other hand, the exhaust port 14 has an O ₂ sensor 4
An exhaust pipe 43 including a three-way catalyst 42 and a muffler (not shown) is connected via an exhaust manifold 41 to which 0 is attached. In addition, the EGR port 15 has a large diameter EG.
It is connected to the downstream side of the throttle valve 28 and the upstream side of the intake manifold 21 via an R pipe 44, and a stepper motor type EGR valve 45 is provided in the pipeline.

The fuel tank 50 is installed at the rear portion of the vehicle body (not shown). Then, the fuel stored in the fuel tank 50 is sucked up by the electric low-pressure fuel pump 51,
It is fed to the engine 1 side via the low-pressure feed pipe 52. The fuel pressure in the low-pressure feed pipe 52 is the first fuel pressure regulator 5 installed in the conduit of the return pipe 53.
4, the pressure is adjusted to a relatively low pressure (3.0 kg / mm ^{2 in} this embodiment, hereinafter referred to as low fuel pressure). The fuel fed to the engine 1 side is fed to each fuel injection valve 4 by a high-pressure fuel pump 55 attached to the cylinder head 2 via a high-pressure feed pipe 56 and a delivery pipe 57. In the case of the present embodiment, the high-pressure fuel pump 55 is of the swash plate axial piston type, is driven by the exhaust side camshaft 12, and is 50 kg / mm ² even during idle operation of the engine 1.
The above discharge pressure is generated. The fuel pressure in the delivery pipe 57 is set to a relatively high pressure (50 in the present embodiment) by the second fuel pressure regulator 59 provided in the conduit of the return pipe 58.
kg / mm ² . Hereinafter, it will be described as high fuel pressure). In the figure,
Reference numeral 60 denotes an electromagnetic fuel pressure switching valve attached to the second fuel pressure regulator 59, which relieves fuel in the ON state and
The fuel pressure in the delivery pipe 57 is set to a predetermined value (for example, 3.0 kg /
mm ² ). Further, 61 is a high-pressure fuel pump 55.
Is a return pipe for returning the fuel, which has been lubricated and cooled, to the fuel tank 50.

An ECU (electronic control unit) is provided in the passenger compartment.
70 is installed in the ECU 70, and a storage device (ROM, RAM, non-volatile RAM) for storing an input / output device (not shown), a control program, a control map, etc.
Etc.), a central processing unit (CPU), a timer counter, etc., and controls the engine 1 as a whole. EC
To the input side of U70, switches and the like for detecting the operating conditions of the air conditioner, the power steering device, the automatic transmission, etc., which become the load of the engine 1 at the time of operation, are connected (none are shown), and each detection signal Is supplied to the ECU 70. The fuel injection valve 4, the ignition coil 19, the EGR valve 45, and the ABV valve 27 described above are provided on the output side of the ECU 70.
In addition to being electrically connected to each other, various warning lights, devices and the like (not shown) are connected.

The ECU 70 determines the ignition timing, the EGR gas introduction amount, etc., including the fuel injection mode and the fuel injection amount, based on the input signals from the various sensors and switches described above, and the fuel injection valve 4, Ignition coil 19, EGR
The valve 45, the ABV valve 27, etc. are drive-controlled. FIG. 4 shows a fuel injection control map, in which the ECU 7 is warmed up after the engine 1 is warmed up.
0 specifies the operation mode to be executed. More specifically, based on the in-cylinder effective pressure (target average effective pressure) Pe obtained from the intake pipe pressure Pb, the throttle opening θTH, etc. and the engine rotation speed Ne, the current fuel is calculated from the fuel injection control map of FIG. In addition to driving the fuel injection valve 4 by searching the injection control region, determining the fuel injection mode and the fuel injection amount, and AB
It also controls the opening of the V valve 27 and the EGR valve 45.

For example, during low load / low speed operation such as idle operation, the latter injection lean region in FIG.
The CU 70 selects the late injection mode (also referred to as the late lean mode) and opens the ABV valve 27 and the EGR valve 40 in accordance with the operating state to provide a lean air-fuel ratio (about 20 to 40 in this embodiment). ) Is injected.
At this time point, the vaporization rate of the fuel rises, and the intake flow flowing from the intake port 13 forms the reverse tumble flow 80 shown by the arrow as shown in FIG. Stored in. as a result,
At the time of ignition, an air-fuel mixture near the stoichiometric air-fuel ratio is formed around the spark plug 3, and it is possible to ignite even with an extremely lean air-fuel ratio as a whole (for example, a total air-fuel ratio of about 40). As a result, CO and HC emissions are extremely small, and NOx emissions are suppressed to a low level by the exhaust gas recirculation. Then, the ABV valve 27 and the EG
Fuel consumption is greatly improved in combination with the reduction of pumping loss due to the opening of the R valve 40. The control of the idle speed according to the increase / decrease of the load is performed by increasing / decreasing the fuel injection amount, so that the control responsiveness becomes very high.

In the latter injection mode, the combustion fluctuation control described later is executed to adjust the EGR amount and the like. Further, in the latter-stage injection mode, the fuel spray injected from the injection valve 4 must reach the spark plug 3 by riding on the above-described reverse tumble flow. Therefore, it is necessary to accurately control the timing of starting and ending the fuel injection.

Further, during low-medium speed running, depending on the load condition and the engine speed Ne, the previous period injection lean region or stoichio feedback region (theoretical air-fuel ratio feedback control region, which is SF / B area), the ECU 70 determines that the lean mode or the S-F
The / B mode (these two modes and the open loop control mode to be described later are collectively referred to as the first term injection mode) is selected, and the fuel is injected so as to have a predetermined air-fuel ratio.

That is, in the first-half lean mode,
A lean air-fuel ratio (about 20 to 23 in this embodiment)
The opening amount of the ABV valve 27 and the fuel injection amount so that
However, in the S-F / B mode, the ABV valve 27 and the EGR valve 4
Opening and closing control of 5 and O ₂Output voltage of sensor 40
The air-fuel ratio feedback control is performed according to in this case
As shown in FIG.
Fuel injection disclosed because the air flow forms a reverse tumble flow 80
By adjusting the timing or end timing, the previous period injection lean
Even in the range, it is lean due to the effect of the turbulence due to the reverse tumble.
Ignition is possible even with an air-fuel ratio. Comparison in S-F / B range
Owing to the relatively high compression ratio, a large output is obtained and O₂
Feedback control keeps the air-fuel ratio close to the theoretical air-fuel ratio.
It has a good drivability because it is maintained, and combustion fluctuations hardly occur.
Is obtained stably and harmful exhaust gas components are
Since it is purified by the medium 42, the amount of NOx emissions is also small
Held in a state.

Since the open loop control range shown in FIG. 4 is set during the rapid acceleration or the high speed running, the ECU 70 selects the first injection mode and closes the ABV valve 27 to throttle opening θTH and engine speed. Depending on Ne, etc.
The fuel is injected so that the air-fuel ratio becomes relatively rich. At this time, the compression ratio is high and the intake flow is the reverse tumble flow 8
In addition to forming 0, the intake port 13 is substantially upright with respect to the combustion chamber 5, so that a high output can be obtained due to the inertia effect.

Further, during coasting operation during medium-high speed traveling, the fuel cut region in FIG. 4 is reached, so the ECU 70 completely stops fuel injection. As a result, the fuel consumption is improved and at the same time, the emission amount of the harmful exhaust gas component is reduced. The fuel cut is immediately stopped when the engine rotation speed Ne becomes lower than the return rotation speed or when the driver depresses the accelerator pedal.

Next, the combustion fluctuation control procedure according to the present invention will be described with reference to the flow charts shown in FIGS. First, the combustion fluctuation detection procedure will be described. The ECU 70 executes a combustion fluctuation detection interrupt routine shown in FIG. 7 every time the crank angle sensor 17 detects a predetermined crank angle position. In this interrupt routine, the ECU 70
Measures the detection time interval of the crank angle position each time the STG signal from the crank angle sensor 17 is input, that is, the time Ti required for the engine to rotate 180 ° at the crank angle. This measurement is performed, for example, by reading the counter value of a counter (not shown) every time the STG signal is input (step S10). Next, the angular acceleration A of the engine is calculated based on the value Ti-1 measured last time and the value Ti this time.
i is calculated by the following equation (M1) (step S12).

[0043]

[Equation 1]

Since the detected angular angle Ai varies in magnitude relatively depending on the engine speed, it is normalized by the fuel injection amount Qi at the time of detection, and this is I
It is stored as an ai value (step S14). Iai = absolute value (Ai / Qi) (M2) Then, the process proceeds to step S16, where the Iai value is the predetermined value CIa.
It is determined whether or not it is larger, that is, whether or not there is a combustion fluctuation that should be a problem from the rotation fluctuation (step S1).
6). If this determination result is negative (No), step S17 described below is skipped and the process proceeds to step S18. However, if the determination is affirmative (Yes), in step S17, the calculation of the V value that is the combustion fluctuation evaluation parameter value is performed. To do. That is, Iai obtained at step S14 this time to the previous value Vi-1
The values are added and stored as the current value Vi, and the process proceeds to step S18.

Vi = Vi-1 + Iai (M3) In this way, when a significant combustion fluctuation occurs, the Iai value is added each time, and this addition is repeated for a predetermined period described later. In step S18, the combustion fluctuation detection count CN
Is being counted. That is, the count value CN is incremented by 1 and stored. Then, it is determined whether or not the count value CN has reached a predetermined value XCN (for example, a value corresponding to 128 strokes of the engine 1) (step S2).
0) If not reached, the routine is ended while the combustion fluctuation is detected for a predetermined period (the period corresponding to the value XCN). When the count value CN reaches the predetermined value XCN, the process proceeds to step S22, the integrated value Vi is stored as the combustion fluctuation evaluation parameter value Vs, and the above-described counter value CN is cleared to the value 0, and the routine ends. The combustion fluctuation evaluation parameter value Vs thus obtained is updated every time a predetermined period (XCN) elapses. The evaluation parameter value Vs is an integrated value of the value Iai representing the magnitude of the combustion fluctuation in each predetermined period, but if the viewpoint is changed, it represents the average value of the magnitude of the combustion fluctuation in the predetermined period.

As the evaluation parameter value of the combustion fluctuation, the angular acceleration of the engine 1 is detected and used in this embodiment, but various modified examples are conceivable, and the magnitude of the vibration of the engine 1 and the cylinder internal pressure are considered. May be detected and the evaluation parameter value may be obtained from these detected values. Further, the cylinder pressure Pi is detected, and the detected value is used as the fuel injection amount Qi.
The value (Pi / Qi) normalized by can be used as the evaluation parameter, or the combustion index BS obtained from the following equation (M0) can be used as the evaluation parameter.

[0047]

[Equation 2]

Here, P (ATDC60) is the in-cylinder pressure of 60 ° after the top dead center, and means the effective pressure (torque) when the combustion pressure rises and becomes stable. P (BTDC60) is 60 before top dead center
The cylinder internal pressure is °, and means the effective pressure (torque) in a state where ignition is not performed (immediately before ignition). P (BTDC120) is the in-cylinder pressure at 120 ° before top dead center, and means the effective pressure (torque) before being substantially compressed. When the combustion index BS exceeds a predetermined value, it may be determined that combustion fluctuation has occurred.

Next, a procedure for controlling the combustion fluctuation based on the combustion fluctuation evaluation parameter value VS obtained as described above will be described with reference to FIG. The combustion fluctuation control routine shown in FIG. 8 is executed every time the crank angle sensor 17 outputs the crank angle signal STG at a predetermined crank position. First, the ECU 70 determines in step S28 whether or not the value of the flag FEGR that is a program control variable is 1. As will be described later, this control variable FEGR is determined to be suspected to be abnormal in the operation of the EGR valve when the control for reducing the EGR amount due to the combustion fluctuation is continuously repeated a predetermined number of times, and this is stored. It is for.

If the determination result in step S28 is negative, the process proceeds to step S30 to execute the EGR correction amount calculation routine. 9 and 10 show the details of this EGR correction amount calculation routine. The ECU 70 first determines whether or not the evaluation parameter value Vs stored in the combustion variation detection routine described above has been updated ( Step S3
00), if it has not been updated, the routine is ended, the process returns to the combustion fluctuation control routine of FIG. 8, and this routine is also ended. That is, even if the routine is executed every time the predetermined crank position is detected, the EGR amount is not corrected unless the evaluation parameter value has been updated.

When the evaluation parameter value Vs is updated, the EGR correction amount according to the Vs value is calculated in the determination steps of steps S302 and S306. More specifically, in step S302, it is determined whether or not the Vs value is larger than the predetermined value CV2. Predetermined value CV2
Is a value set by an experiment or the like to determine that the combustion fluctuation is large. If the determination result is negative, step S304 is not executed and step S30 is performed.
6, the step S304 is executed when the Vs value is larger than the predetermined value CV2, and the correction amount ΔERG for controlling the EGR valve 45 to the closing side is calculated.

In the calculation of the correction amount .DELTA.ERG in step S304, first, the current product value SVi is added to the previous product value SVi-1 to obtain the current product value SVi, which is stored. SVi = SVi-1 + Vs (E1) Then, based on the product value SVi and the evaluation parameter value Vs, the correction amount .DELTA.EGR is calculated by the following equation (E2).

ΔEGR = Kpc * Vs + Kic * SVi (E2) where “*” is a multiplication symbol (the same applies hereinafter), and K
pc and Kic are feedback gains of the proportional term and integral term when the EGR valve is closed. These coefficient values Kpc and Kic are
It is set to a predetermined negative value by referring to the graph of the Pi fluctuation rate with respect to the EGR position shown in FIG. In particular, the proportional term coefficient Kpc is set to a value (a value that changes abruptly) that is approximately the same as the slope of the Pi fluctuation rate near the fluctuation limit, as shown by the chain double-dashed line in FIG.

In step S306, the Vs value is the predetermined value CV.
Determine if it is less than 1. Predetermined value CV1 (CV
1 <CV2) is a value set by an experiment or the like to determine that the combustion fluctuation is small. If the determination result is negative, the process proceeds to step S310 without executing step S308. However, if the Vs value is smaller than the predetermined value CV1, step S308 is executed, and the correction amount ΔERG for controlling the EGR valve 45 to the open side is calculated.
If the evaluation parameter value Vs is smaller than the predetermined value CV1,
Combustion fluctuation is small and preferable from the viewpoint of drivability, but from the viewpoint of exhaust gas characteristics, the EGRE amount should be further increased to reduce NO.
x means that there is room to reduce emissions.
Therefore, when the evaluation parameter value Vs is smaller than the predetermined value CV1, the target position of the ERG valve is corrected to the open side so as to increase the EGR amount. Accordingly, when the combustion fluctuation is small, the EGR amount can be increased within a range where the combustion fluctuation does not occur, and the exhaust gas performance and the fuel consumption can be improved.

The correction amount .DELTA.ERG in step S308 is calculated by adding the current evaluation parameter value Vs to the previous product value SVi-1 and the current product value SVi (= SVi-1 + Vs) by the equation (E1) as in step S304. ) And memorize this. Then, the product value SVi and the evaluation parameter value Vs
Based on, the correction amount ΔEGR is calculated from the following equation (E3). ΔEGR = Kpo * Vs + Kio * SVi (E3) Here, Kpo and Kio are feedback gains of the proportional term and the integral term when the EGR valve is open, and these values are also the Pi variation with respect to the EGR position shown in FIG. It is set to a positive predetermined value by referring to the rate graph. Especially the proportional term coefficient K
As indicated by the alternate long and short dash line in FIG. 1, po is set to a value (a value that changes gently) so that the EGR position has a slope substantially the same as the slope of the Pi fluctuation rate below the fluctuation limit.

If the Vs value is neither larger than the predetermined value CV2 nor smaller than the predetermined value CV1, the EGR amount is an appropriate amount, the correction amount for correcting the EGR valve position is not calculated, and step S310 is executed. It Step S31
At 0, the learning correction value for the EGR position is calculated. First, the learning correction amount LEGRi for this time is calculated from the following equation (E4).

LEGRi = Kp * Vs (E4) As the correction coefficient Kp, the above-mentioned correction coefficient value Kpc is used when the EGR position is corrected to the closing side, and when it is corrected to the opening side. The above-mentioned correction coefficient value Kpo is preferably used, but it may be experimentally set to an appropriate value. Next, the average value ΔEGRL of the learning correction value LEGRi obtained this time and the correction value ΔEGRLi-1 obtained so far is calculated by the following equation (E5).
Ask more.

ΔEGRL = α * ΔEGRLi-1 + (1-α) * LEGRi (E5) where α is a weighting coefficient for obtaining the average value and the value 1
It is set to a smaller positive appropriate value. If α is a value close to 1, the learning value ΔEGRi changes little with time.
When the learning correction value is calculated, step S31 in FIG.
In step 1, the current learning correction value ΔEGRL is compared with the stored learning correction value ΔEGRLE, and it is determined whether or not the deviation between the two is larger than the predetermined value ΔEo. If the deviation is small, the learning correction value is not updated, but if the deviation between the current learning correction value and the stored learning correction value is large (if the determination result in step S310 is affirmative), the learning correction value is determined. The stored value ΔEGRLE of is rewritten to the learning correction value ΔEGRL this time (step S312), and the routine ends.

The EGR correction amount ΔEGR and the learning correction value ΔEGRLE obtained as described above are E shown in FIG.
It is called when the GR valve drive routine (built into the main routine) is executed, and is used to calculate the EGR target position PEGR shown by the following equation (M4). And EGR
When the setting of the target position PEGR is completed, a drive signal corresponding to the set value is output to the EGR valve 45, and the EGR valve 4
5 is opened to a position corresponding to the target position PEGR (step S110).

PEGR = PEGR0 + ΔEGR + ΔEGRLE (M4) Note that PEGR0 in the formula (M4) is a basic position, and is set according to the engine speed, the load, the target air-fuel ratio, and the like. In this way, the EGR amount is constantly controlled to the optimum value by the correction based on the combustion fluctuation and the learning correction with respect to the basic position set according to the operating region of the engine 1.

Returning to step S30 in FIG. 8, when the calculation of the EGR correction amount is completed, the process proceeds to step S34, where the correction amount ΔEGR is a negative value, that is, the calculated ΔEGR.
Based on the GR value, it is determined whether the EGR valve 45 is drive-controlled to the closing side. If the EGR valve 45 is not controlled to be closed, it means that no problematic combustion fluctuation has occurred. In such a case, step S36 is performed.
At, the counter value N is reset to 0 and the routine ends.

When the EGR valve 45 is drive-controlled to the closing side (when the determination result of step S34 is affirmative), the process proceeds to step S38, the counter value N is incremented by 1 and the process proceeds to step S40. The counter N is for counting the number of times (period) that the EGR reduction correction control is continuously executed. In step S40, the EGR reduction correction control is continuously executed for a predetermined period NEGR from the start (N> NEGR holds), and the correction amount Δ
Whether EGR exceeds a predetermined value XE (absolute value ΔEGR> X
E) Determine whether or not. If the two conditions are not satisfied at the same time, the routine is terminated, but if they are satisfied, E
It is determined that the valve operation of the GR valve 45 may be abnormal, and the failure flag FEGR is set to the value 1 in step S42, and then the EGR / air-fuel ratio control routine is executed when the combustion fluctuation is large (step S42). S50). Once the failure flag FEGR is set to the value 1, the determination result in step S28 described above becomes affirmative, and the routine of step S50 is repeatedly executed until the value is reset to 0.

12 and 13 show a flowchart of the EGR / air-fuel ratio control in the case where the state of large combustion fluctuations continues, and the ECU 70 first sets the target position PEGR of the EGR valve 45 to a predetermined decrease value at the time of failure, In this embodiment, the value PEGRF0 corresponding to the fully closed position is set, and the drive signal corresponding to this set value is output (step S500). EGR
When the valve 45 does not move due to being stuck due to soot or the like, the valve opening degree of the EGR valve 45 does not change even if such a drive signal is output, but as a control at the time of failure, this step is executed every time. And outputs a signal for driving the EGR valve 45 to the fully closed position.

Next, it is determined whether or not the evaluation parameter value Vs updated and stored in the above-described combustion fluctuation detection routine has been updated (step S501), and if it has not been updated, this routine is ended. At the same time, the routine returns to the combustion fluctuation control routine of FIG. 8 and this routine is finished.
That is, even if the routine is executed every time the predetermined crank position is detected, the target air-fuel ratio AF is not corrected unless the evaluation parameter value has been updated.

When the evaluation parameter value Vs is updated, the air-fuel ratio correction amount corresponding to the Vs value is calculated in the determination steps of step S502 and step S504. More specifically, in step S502, it is determined whether or not the Vs value is larger than the predetermined value CV2. Predetermined value CV2
Is the same as the discriminant value used in step S302 of FIG. 9, but a discriminant value different from this may be set. If the determination result is negative, the process proceeds to step S504 without executing step S503, but the Vs value is the predetermined value CV2.
If it is larger, step S503 is executed, and the correction amount ΔAF for correcting the target air-fuel ratio to the rich side is calculated.

The calculation of the correction amount ΔAF in step S503 is performed by the same method as the method of calculating the EGR correction amount. More specifically, the product value SVi is calculated by the above-mentioned equation (E1) using the combustion fluctuation evaluation parameter VS, and then,
The air-fuel ratio correction amount ΔAF is calculated by the following formula (F1). ΔAF = Kpr * Vs + Kir * SVi (F1) where Kpr and Kir are feedback correction coefficients for the proportional term and the integral term, and feedback correction coefficient values Kpc, Kic (steps in FIG. 9) at the time of EGR amount correction. These values may be set according to the same idea as in S304) or may be set experimentally as appropriate.

In step S504, the Vs value is the predetermined value CV.
Determine if it is less than 1. This predetermined value CV1
(CV1 <CV2) is also a value set by an experiment or the like in order to determine that the combustion fluctuation is small.
Is the same as the discriminant value used in step S306 of
A discriminant value different from this may be set. If the determination result is negative, the process proceeds to step S506 without executing step S505, but if the Vs value is smaller than the predetermined value CV1, step S505 is executed to correct the target air-fuel ratio to the lean side. The correction amount AF is calculated. If the evaluation parameter value Vs is smaller than the predetermined value CV1, combustion fluctuation is small and it is preferable from the viewpoint of drivability, but lean combustion is performed from the viewpoint of exhaust gas characteristics and fuel consumption, and the ABV valve 27 is used.
This means that there is room for increasing the amount of lean air from the vehicle to reduce NOx emissions and improve fuel efficiency. Therefore, when the evaluation parameter value Vs is smaller than the predetermined value CV1, the target air-fuel ratio is corrected to the lean side so as to increase the lean air amount. This makes EGR
Even when the combustion fluctuation cannot be controlled by the EGR reduction control due to the failure of the valve 45, the combustion fluctuation is controlled by adjusting the air-fuel ratio, and when the combustion fluctuation is small, the combustion fluctuation does not occur within a range. By correcting the target air-fuel ratio to the lean side, exhaust gas performance and fuel economy can be improved.

The calculation of the correction amount ΔAF in step S505 is performed by adding the current evaluation parameter value Vs to the previous product value SVi-1 and the current product value SVi (= SVi-1 + Vs) by the equation (E1) as in step S503. ) And memorize this. Then, based on the product value SVi and the evaluation parameter value Vs, the correction amount ΔAF is calculated by the following formula (F2). ΔAF = Kpl * Vs + Kil * SVi (F2) where Kpl and Kil are feedback gains of the proportional term and the integral term, and feedback correction coefficient values Kpo and Kio at the time of EGR amount correction (step S308 in FIG. 9). These values may be set according to the same idea as in (see) or may be set experimentally as appropriate. When correcting the air-fuel ratio to a lean value, the ΔAF value is set to a negative value.

If the Vs value is neither larger than the predetermined value CV2 nor smaller than the predetermined value CV1, the target air-fuel ratio AF is a proper value, and the correction amount ΔAF for correcting the target air-fuel ratio is set to the value 0 ( Step S506) and step S507 are executed. In step S507, the present target air-fuel ratio AFi is calculated by the following formula (F3) based on the correction amount ΔAF obtained as described above.

AFi = AFi-1−ΔAF (F3) The initial value of the previous target air-fuel ratio AFi-1 is the reference target air-fuel ratio A set in the region where the engine 1 is currently operating.
Set to Ft. This time, the target air-fuel ratio AFi gradually changes to the rich side or the lean side according to the correction amount ΔAF every time this step is repeatedly executed.

When the calculation of the current target air-fuel ratio AFi is completed as described above, the evaluation parameter value Vs is reset to the value 0 in step S507, and then the current target air-fuel ratio AFi is reset.
Deviation from the stoichiometric air-fuel ratio (eg, 14.7) is a predetermined value X
Is it below AF0 (absolute value (AFi -14.7) <
It is determined whether or not XAF0 is established (step S5).
08). The predetermined value XAF0 is based on the air-fuel ratio at which a so-called rich misfire occurs when the target air-fuel ratio (overall air-fuel ratio) is made rich in the late lean mode and the local air-fuel ratio near the spark plug 3 becomes overrich. It is set.
If the determination result in step S508 is negative, the process proceeds to step S510, and the second lean mode operation is continuously instructed.

FIG. 14 shows a flow chart of an ABV valve drive routine (executed in the main routine) executed during the latter lean mode operation.
The correction amount ΔQa of the lean air supplied through the ABV valve 27 is calculated by the following formula (F4) (step S13).
0). ΔQa = (ΔAF / AFi) * Qa (F4) where ΔAF and AFi are the same as those in step S503 described above.
(Or S505) and the air-fuel ratio correction amount and the target air-fuel ratio calculated in step S507. Qa is an intake air amount and may be obtained by multiplying the boost pressure Pb by the volume efficiency obtained from the map by the detected boost pressure Pb or throttle valve opening θTH and the engine speed Ne. You may make it detect directly by an air flow sensor.

Next, the correction amount Δ obtained as described above
The ABV valve 27 is driven based on Qa to decrease or increase the lean air amount by the correction amount ΔQa (step S13).
2). In this way, the target air-fuel ratio AFi is adjusted by the correction amount ΔA.
The fuel is supplied to the cylinder because the valve is gradually enriched (enriched) or leaned (diluted) to F and the ABV valve 27 is also gradually closed or opened according to the air-fuel ratio correction amount ΔAF. The amount of fuel discharged is kept substantially constant, torque fluctuation does not occur, and drivability does not deteriorate.

Returning to step S508 in FIG. 13, if the determination result in this step is affirmative, that is, combustion fluctuation continues to occur, and the deviation between the target air-fuel ratio AFi and the theoretical air-fuel ratio becomes smaller than the predetermined value XAF0. If so, the rich misfire may occur in the fuel control in the late lean mode any longer, and the process proceeds to step S512 and the ABV valve 27 is activated.
After outputting a drive signal for fully closing the
Then, the command signal for the previous period stoichiometric mode operation is output. By this command signal, as described above, fuel is injected mainly into the combustion chamber in the intake stroke, and the engine 1
Although the intake air may be supplementarily supplied from the idle control valve 24, it is mainly supplied via the throttle valve 29, and is adjusted so that the overall air-fuel ratio becomes substantially the theoretical air-fuel ratio. In the first-stage stoichio mode operation, a mixture having a substantially stoichiometric air-fuel ratio is generated in the cylinder, so stable combustion with little combustion fluctuation is obtained, and good drivability is achieved despite the failure of the EGR valve 45. Can be secured. Further, since the basic target air-fuel ratio is set to the stoichiometric air-fuel ratio, the exhaust gas purifying action of the three-way catalyst 42 can be efficiently performed, and the exhaust gas characteristics such as NOx are improved.

As described above, when there is a risk of deterioration of drivability and deterioration of exhaust gas characteristics due to failure of the EGR valve during lean combustion, switching is made to the stoichiometric operation in the previous period in which stable combustion is obtained, and the EGR valve 45 is also fully closed. In order to switch to the position, the fail-safe function at the time of failure will be exhibited. Further, such a fail-safe function can be realized at low cost because it is not necessary to provide a special sensor. ( Reference Mode 1 ) Next, reference will be made to a description of an embodiment of the present invention.
As a first aspect, an apparatus for controlling combustion fluctuation during the first-term lean mode operation of the in-cylinder gasoline engine described above will be described.

During the first-half lean mode operation, as described above, the engine is operated in a fuel lean state with an overall air-fuel ratio of about 20 to 23, and the ABV valve 45 is opened to recirculate an appropriate EGR amount to the engine 1 to make it lean. Even with combustion, NOx emissions are suppressed within an allowable range, and pumping loss is reduced to improve fuel efficiency.

Even during this first-term lean mode operation, the above-described combustion fluctuation detection interrupt routine of FIG. 7 is executed to detect the evaluation parameter value Vs. Then, FIGS.
The combustion fluctuation control routine shown in is executed, the combustion fluctuation is constantly monitored by the above-mentioned evaluation parameter value Vs, and the combustion fluctuation control is executed. In the combustion variation control routine of the reference mode 1 , the ECU 70 firstly executes step S of FIG.
Flag FLG1 which is a program control variable in 60
It is determined whether or not the value 1 is set in. This flag FLG1 is set when it is determined that the combustion fluctuation is large as will be described later, and the control for reducing the EGR amount to the predetermined reduction value is executed. The determination of step S62 described later is repeatedly executed.

If the flag FLG1 is not 1 and the determination result in step S60 is negative, step S60
In step 62, it is judged if the evaluation parameter value Vs is larger than the predetermined value KV2, that is, if the combustion fluctuation is larger than the allowable value KV2. This discriminant value KV2 may be the same as the discriminant value CV2 used in the first embodiment. When the combustion fluctuation larger than the predetermined value KV2 has not occurred, nothing is done and the routine is ended.

When the determination result in step S62 is affirmative and it is determined that the combustion fluctuation is large, the deviation ΔVE between the evaluation parameter value Vs detected this time and the above-mentioned predetermined value KV2 is calculated (step S63). ΔVE = Vs−KV2 (G1) Then, the correction amount ΔPEGR of EGR according to the deviation ΔVE
From the ΔVE · PEGR map (step S6)
4). This map is stored in advance in the storage device of the ECU 70 described above, and the larger the PEGR value is, the larger the ΔVE is according to the current target position PEGR of the EGR valve 45 and the deviation ΔVE. Large correction amount Δ
PEGR is calculated. These map values are experimentally obtained, and are appropriately set in consideration of the exhaust gas performance and the output performance. Thus, the correction amount ΔPEGR is set to a value according to the deviation ΔVE, so that the EGR amount is not excessively reduced and corrected, and the exhaust gas characteristics and the fuel consumption are not significantly deteriorated.

When the calculation of the correction amount ΔPEGR is completed, EG
The current target position PEGRi of the R valve 45 is set to a predetermined decrease value by the following equation (G2), and a drive signal corresponding to this set value is output to close the EGR valve 45 to the predetermined decrease value. PEGRi = PEGRi-1−ΔPEGR (G2) where PEGRi-1 is the previous target position of the EGR valve 45. When the EGR valve 45 is operating normally, the predetermined reduction value PEGRi set this time does not deteriorate the exhaust gas characteristics, particularly the NOx emission amount, to a predetermined amount or more,
The combustion fluctuation is set to a value that can be reduced, and in some cases it may be a value corresponding to the fully closed position of the EGR valve 45. In this case, the normal combustion fluctuation can be promptly and reliably reduced.

FIG. 17 shows changes with time in the evaluation parameter value Vi, the target position PEGR, and the target air-fuel ratio AF. As shown in FIG. 17A, the Vi value exceeds the predetermined value KV2 at time t0, Vs in step S62
It is determined that the value is larger than the predetermined value KV2,
After the time t0, the time t1 is reached when the determination result in step S20 becomes affirmative. Then, at the time point t1, the EGR valve 45 is closed to the closed position where the EGR valve 45 is throttled to the predetermined decrease value smaller by ΔP EGR as described above (time point t1 in FIG. 17).

Then, in step S66, the flag F
The value 1 is set in LG1, and the counter value CT is advanced by 1 in step S68 (CT = CT + 1).
Then, it is determined whether or not the counter value CT is larger than the predetermined value XT1 (step S70). It is preferable to wait until the time required for the EGR valve 45 to close to the predetermined decrease value, and the CT counter (timer) is set to the predetermined value XT1 (XT1 value is set in step S2 in FIG. 7) set corresponding to this period.
It is preferable to set it to a value sufficiently larger than the discriminant value XCN used at 0). Step S7
If the determination result of 0 is negative, the EGR amount reduction control is being performed, and in such a case, the routine is ended. Then, at the time of execution of the next routine, the flag FLG1
Is set to the value 1 in step S66 described above, the determination result in step S60 is affirmative, the process proceeds to step S68 described above, and this step and S70 are repeatedly executed until the counter value CT reaches the XT1 value. It will be.

When the period corresponding to the XT1 value has elapsed, the determination result of step S70 becomes affirmative, and step S72 of FIG. 16 is executed. In this determination step, it is determined whether or not the evaluation parameter value Vs is larger than the predetermined value KV3. The predetermined value KV3 is smaller than the above-mentioned predetermined value KV2, but is larger than the value obtained from the combustion fluctuation that occurs when the EGR valve 45 operates normally and the EGR amount decreases to the above-mentioned predetermined decrease value. It is set to an appropriate value.

If the determination result in step S72 is negative,
That is, when the Vs value is smaller than the predetermined value KV3, E
This means that the effect of suppressing the combustion fluctuation is sufficiently obtained by the GR reduction control. In such a case, the flag FLG1
The value is reset to 0 and the routine ends. On the other hand, if the determination result of step S72 is affirmative, that is, EG
If the combustion fluctuation is not sufficiently suppressed even by the R reduction control, the routine proceeds to step S74, where the deviation ΔVA between the present evaluation parameter value VS and the above-mentioned predetermined value KV3 is calculated, and ΔVA = Vs−KV3. G3) Next, according to the deviation ΔVA, the correction amount ΔAF of the target air-fuel ratio
Is calculated from the ΔVA · AF map (step S7).
5). This map is also stored in advance in the storage device of the ECU 70 described above, and the current target air-fuel ratio AF and the deviation ΔV are stored.
Depending on A, the larger the AF value, the larger, and ΔV
The larger A is, the larger the correction amount ΔAF is calculated. These map values are set experimentally, and are set to appropriate values that are slightly lean outside the throttle fully open region. in this way,
Since the correction amount ΔAF is set to a value according to the deviation ΔVA, the target air-fuel ratio is not over-enriched and the exhaust gas characteristics and fuel consumption are not significantly deteriorated.

Next, the routine proceeds to step S76, where A is set according to the correction amount ΔAF of the target air-fuel ratio calculated as described above.
The intake air amount ΔQa to be corrected by the BV valve 27
Calculate from (F3). Then, the ABV valve 27 is driven to the closing side based on the calculated correction amount ΔQa, and the lean air amount supplied to the engine 1 via the ABV valve 27 is corrected by the correction amount ΔQa.
Just (step S78). In this way, ABV
The valve 27 is suddenly throttled to the target opening degree, and the target air-fuel ratio in the combustion chamber is changed to a predetermined enrichment value on the fuel rich side to become rich (at time t2 in FIG. 17A). The predetermined enrichment value may be set to a value that can reduce the combustion fluctuation without deteriorating the fuel consumption by a predetermined value or more, and is preferably set to a value corresponding to the theoretical air-fuel ratio.

As described above, the EGR reduction control by the EGR valve 45 and the air-fuel ratio enrichment control by the ABV valve 27 are
Although it takes time for the valve operation to change to the target valve opening, the target position PEGR and the target air-fuel ratio AF are changed stepwise (see FIGS. 17B and 17C), so the combustion fluctuation is controlled with good responsiveness. can do. The combustion fluctuation control device of the first embodiment has been described by taking as an example the one applied to the control of the combustion fluctuation during the previous period lean mode operation of the in-cylinder injection engine as described above. It can be similarly applied to the control of combustion fluctuation during operation. ( Reference Mode 2 ) Next, reference will be made to a description of an embodiment of the present invention.
As a second aspect, a control device for controlling the combustion fluctuation during the above-described lean mode operation of the in-cylinder gasoline engine, which is similar to the first aspect but a different aspect, will be described. This reference form
In state 2 , as shown in FIG. 18, when a state in which the combustion fluctuation is large is detected (at time t11), the EGR valve 45 sets the target position value to a gradually smaller value and gradually closes the valve. Then, the EGR amount gradually decreases to a predetermined decrease value. Then, at the time point when the EGR valve 45 is closed to the target valve opening degree (time point t12), the target air-fuel ratio is gradually changed to a predetermined enriched value on the rich fuel side to reduce the combustion fluctuation. It is a thing.

Details of the combustion fluctuation control according to the second embodiment as described above will be described with reference to the flowcharts of FIGS. 19 to 22. During the first-term lean mode operation, as described above, the operation is performed in a fuel lean state with an overall air-fuel ratio of about 20 to 23, and the ABV valve 45 is opened to return an appropriate EGR amount to the engine 1. There is no change. Further, even during the first-term lean mode operation, the combustion variation detection interrupt routine of FIG. 7 described above is executed, and the evaluation parameter value Vs is still detected. Then, the combustion fluctuation control routine shown in FIGS. 19 to 22 is executed, the combustion fluctuation is constantly monitored by the above-described evaluation parameter value Vs, and the control of the combustion fluctuation is executed as follows.

In the combustion fluctuation control routine of the second embodiment ,
The ECU 70 firstly executes steps S80 to S82 of FIG.
At, it is determined whether or not the value 1 is set in the flags FLG2 to FLG4. These flags are program control variables, and as will be described later, the evaluation parameter value Vs
And the target position value PEGR are set, and their initial values are 0.

While the combustion fluctuation is not detected, step S
The determination results of 80 to S82 are negative, and step S
In step 83, it is judged if the evaluation parameter value Vs is larger than the predetermined value KV12, that is, if the combustion fluctuation is larger than an allowable value. This discriminant value KV12 may be the same as the discriminant value KV2 used in the second embodiment. If there is no combustion fluctuation such that the Vs value is larger than the predetermined value KV12, nothing is done and the routine is ended.

When the determination result in step S83 is affirmative and it is determined that the combustion fluctuation is large (t1 in FIG. 18).
1), the deviation ΔVE between the evaluation parameter value Vs detected this time and the above-mentioned predetermined value KV12 is calculated in the same manner as in the first embodiment (step S84), and ΔVE = Vs−KV12 (G4) , EGR correction amount ΔPEGR according to the deviation ΔVE,
It is read from the ΔVE / PEGR map (step S85).
This map may be the same as the map of the reference embodiment 1 described above, but may be another map that conforms to the reference embodiment 2 , and its map value is experimentally obtained in advance as in the reference embodiment 1, and is based on the combustion limit. EC set to a value on the slightly closed side
It is stored in the storage device of U70. Thus, the correction amount ΔPEGR is set to a value according to the deviation ΔVE,
The EGR amount is not excessively reduced and corrected, and the exhaust gas characteristics and the fuel economy are not significantly deteriorated.

When the calculation of the correction amount ΔPEGR is completed, the previous target position PEGRi-1 of the EGR valve 45 is changed to the valve closing start position PEG.
It is stored as RS (= PEGRi-1). Then, the value 1 is set in the flag FLG4 and the process proceeds to the next step S86. In step S86, the current target position PEGRi of the EGR valve 45 is calculated from the following equation (G5). Further, the correction amount ΔPEGR calculated in step S85 by the following equation (G6) is used as an initial value, and a predetermined amount KEGR is sequentially subtracted from this value, and the current correction remaining amount ΔPEGRi is stored for each subtraction.

PEGRi = PEGRi-1−KEGR (G5) ΔPEGRi = ΔPEGRi-1−KEGR (G6) where PEGRi-1 is the previous target position value of the EGR valve 45. Then, the current correction value amount Δ calculated by the equation (G6)
It is determined whether PEGRi has become 0 or less (step S8).
7), if not less than 0, the process proceeds to step S88 and the above equation (G
A drive signal corresponding to the current target position value PEGRi obtained in 5) is output to set the EGR valve 45 to the current target position value P.
Close the valve to EGRi. While the determination result of step S87 is negative, the flag value FLG4 in step S82
The step S86 and the step S87 are repeatedly executed according to the determination of the step S86, and the target position value PEGR is gradually set to a smaller value as shown between the time points t11 and t12 in FIG. To be closed.

On the other hand, if it is determined in step S87 that the current correction remaining amount ΔPEGRi calculated by the equation (G6) is 0 or less, step S89 is executed and the current target position value is calculated by the following equation (G7). Calculated again. PEGRi = PEGRS-ΔPEGR (G7) The value PEGRS and the value ΔPEGR in the above equation (G7) are calculated in step S.
The value calculated and stored at 85 is used. The current target position value PEGRi set in this way is EC
The drive signal corresponding to the target position value is constantly output while being stored in the storage device of U70.
The valve position of 5 is maintained at the target position value PEGRi this time.

In this way, the EGR valve 45 is closed and the EGR valve is closed.
When the EGR valve 45 is operating normally, the exhaust gas characteristic, especially the NOx emission amount, is deteriorated to a predetermined amount or more by reducing the amount to a predetermined decrease value that is smaller by the correction value ΔPEGR at the position value. Combustion fluctuation can be reduced. Also in this reference embodiment 2 , the above-mentioned predetermined decrease value may be a value corresponding to the fully closed position of the EGR valve 45, and in this case, the normal combustion fluctuation can be promptly and surely reduced.

In step S89, when the output of the target position value PEGRi is completed, the flag FLG3 is set to the value 1 to store that the EGR reduction control is completed. When the EGR reduction control is completed, step S90 is executed, and it is determined again whether or not the current evaluation parameter value Vs is larger than the above-mentioned determination value KV12. If this determination result is affirmative, it means that the determination result is the same as the determination result in step S83 described above, even though the EGR reduction control was performed, and the combustion fluctuation is still large. That is, although the EGR valve 45 is driven to the closing side, the EGR valve 45 is likely to be stuck due to soot or the like, failing to close, and malfunctioning. In such a case, it is memorized that the EGR valve 45 is out of order by determining that the EGR valve 45 is out of order, setting a failure flag, turning on a warning light (not shown), and the like. To warn that there is a failure (step S91). Then, the ECU 70
Is a control at the time of failure predetermined by the failure flag,
For example, the late injection lean mode operation and the early injection lean mode operation are prohibited, and the stoichio feedback operation is executed. This failure flag may be reset when the ignition key switch is turned off and the engine 1 is once inactivated, and then the ignition key switch is turned on again. In this case, if the EGR valve 45 is still in the failed state when the engine is restarted, the failure flag is set again in step S91.

If the determination result of step S90 is negative, it means that the EGR reduction control has an effect of suppressing the combustion fluctuation. In this case, the EGR valve 45 is operating and there is no malfunction. The above step S91 is skipped and the process proceeds to step S92. In this step, it is judged whether or not the evaluation parameter value Vs is larger than the judgment value KV13. This discriminant value KV13 is set to be smaller than the above-mentioned discriminant value KV12, and may be the same value as the discriminant value KV2 of the first embodiment . Further, it is desirable to set it to a value larger than the discriminant value CV1 of the first embodiment.

If the determination result in step S92 is negative, it is determined that the combustion fluctuation can be sufficiently suppressed by the EGR reduction control, and the combustion fluctuation control by adjusting the air-fuel ratio described later is not performed. Then, the flag FLG3
FLG4 is reset to the value 0, and the routine ends. If the determination result of step S92 is affirmative, the EGR reduction control had an effect of suppressing combustion fluctuation, but it is determined that the effect is not sufficient, and step S9 is performed.
The combustion fluctuation is controlled by the air-fuel ratio of 4 or less. In step S94, the deviation ΔVA between the current evaluation parameter value Vs and the above-mentioned predetermined value KV13 is calculated, and ΔVA = Vs−KV13 (G7) Then, the correction amount ΔAF of the target air-fuel ratio according to the deviation ΔVA.
Is calculated from the ΔVA · AF map (step S9)
5). This map may be the same as the map used in the reference embodiment 1 , or a map adapted to the reference embodiment 2 may be experimentally set appropriately. In this way, since the correction amount ΔAF is set to a value according to the deviation ΔVA, the target air-fuel ratio is not excessively enriched and corrected,
Exhaust gas characteristics and fuel economy are not significantly deteriorated.

Next, in step S96, the flag F
After setting the value 1 to LG2, the process proceeds to step S97,
The correction amount ΔQa of the lean air supplied to the engine 1 via the ABV valve 27 will be calculated. In the calculation of the correction amount in step S97, since the value 1 is set in the flag FLG2, step S97 is immediately executed by the determination in step S80 described above, and this step S is repeatedly executed. ..

The current correction amount ΔQai in step S97 is calculated by the equations (G8) and (G9). AFi = AFi-1-dAF (G8) ΔQai = (dAF / AFi) * Qai (G9) ΔAFi = ΔAFi-1-dAF (G10) where dAF is the amount per engine step It is a predetermined enrichment amount (correction amount) that determines the enrichment speed of the air-fuel ratio, and if this value is set to a large value, combustion fluctuations are quickly suppressed,
Since there is a possibility that torque fluctuations may occur, these are taken into consideration and set to an appropriate value. AFi and AFi-1 are target air-fuel ratios of the present time and the previous time, respectively. ΔAFi means the correction remaining amount at this time, and the correction remaining amount ΔAFi-at the previous time is set with the correction amount ΔAF obtained in step S95 as an initial value.
It is obtained by subtracting the predetermined concentration amount dAF from 1 each time.

When the correction amount ΔQai is calculated as described above, the ABV valve 27 is driven to the closing side based on the calculated correction amount ΔQai, and the lean air amount supplied to the engine 1 via the ABV valve 27 is calculated. Narrow down the correction amount ΔQai (step S
98). In this way, the target air-fuel ratio AF is set to the value shown in FIG.
As shown in FIG. 8 (c), the lean air supplied to the engine 1 via the ABV valve 27 is gradually enriched (enriched) toward the predetermined enrichment value, and the lean enriched air also corresponds to the predetermined enrichment amount dAF. The fuel amount injected and supplied from the fuel injection valve 4 into the cylinder is maintained substantially constant, and the air-fuel ratio (predetermined enrichment value) in which combustion fluctuation is less likely to occur while securing the required torque is maintained. I will shift to driving in.

When the air-fuel ratio correction remaining amount ΔAFi calculated in step S97 becomes 0 or less (the determination result in step S99 is affirmative, the time t13 in FIG. 18C), the flag FLG2 is set to 0 in step S100.
To reset the routine to end. Flag FLG
When 2 is reset, the determination of step S92 is executed again. If the combustion fluctuation is sufficiently suppressed by the air-fuel ratio enrichment control and the evaluation parameter value Vs is less than or equal to the predetermined determination value KV13, in step S93, the flag FLG is set.
The routines 3 and 4 are reset to 0 and the routine is terminated. On the other hand, if the result of the determination in step S92 is negative, the steps from step S94 onward are executed again and the deviation ΔVA between the evaluation parameter value Vs and the predetermined determination value KV13.
The air-fuel ratio is enriched by the enrichment amount according to.

In the second embodiment as well, the combustion fluctuation control device has been described as an example in which it is applied to the control of the combustion fluctuation during the previous lean mode operation of the in-cylinder injection engine. It can be similarly applied to control of combustion fluctuation during lean combustion operation of the engine. Second Example Next, a second example which is a modified example of the second embodiment will be described. In the second embodiment as well, the combustion fluctuation control during the previous lean mode operation of the in-cylinder gasoline engine will be described as an example, but the combustion fluctuation control during the lean combustion operation of the intake passage injection type engine is similarly performed. Can be applied.

In this embodiment, as shown in FIG. 23, when a state where the combustion fluctuation is large is detected (at time t21), E
The GR amount is once changed to an intermediate decrease value (a value corresponding to ΔPEGRM in the figure) having a smaller decrease amount than a predetermined decrease value (a value corresponding to ΔPEGR in terms of the target position value of the EGR valve 45). Then, after the EGR amount is reduced to the intermediate reduction value, the EGR amount is gradually reduced toward the above-described predetermined reduction value (between t21 and t22 in FIG. 23). EG at this time
Decreasing amounts of R amount may be set to the same value as the reference embodiment 2 correction amount KEGR, it may be set to a value compatible with the second embodiment. When the EGR amount reaches a predetermined decrease value (at time t22), the timer measures the elapsed time and waits for a predetermined period T1. The EGR reduction control ends, and the EG
By starting the air-fuel ratio enrichment control after waiting for the R amount to stabilize, it is possible to prevent the air-fuel ratio from varying due to the influence of EGR. When the gradual decrease amount KEGR is set to a small value and the EGR amount is gradually decreased, the predetermined period T1 may be 0. That is, the waiting period may not be provided. In some cases, the measurement of the elapsed time by the timer may be started at the time when the EGR amount is reduced to the above-described intermediate decrease value (time t21 in FIG. 23).

At the time when the predetermined period T1 has elapsed (t23 in FIG. 23)
At the time point), as in the second embodiment , the evaluation parameter value Vs
Is greater than a predetermined determination value KV23, and if it is determined that the combustion fluctuation is not sufficiently suppressed (Vs> KV23), the air-fuel ratio enrichment control is started. In this air-fuel ratio enrichment control, the target air-fuel ratio AF has an intermediate enrichment value (a value smaller by ΔAFM, which is a smaller enrichment amount than a predetermined enrichment value on the fuel rich side (a value smaller by the correction amount ΔAF). , ΔAFM <ΔAF). In this way, once the target air-fuel ratio is set to the intermediate enrichment value, it is enriched (enriched) to the predetermined enrichment value at once.
It is possible to prevent a marked deterioration in fuel consumption.
Then, after the target air-fuel ratio AF is once changed to the intermediate enrichment value (at time t23 in FIG. 23 (c)), it is gradually changed to a smaller value toward the above-mentioned predetermined enrichment value. The gradual decrease amount dAF of the target air-fuel ratio in this case is the same as the value used in the second embodiment.
It may be of, or may be set experimentally to a value compatible with the second embodiment. As described above, excessive enrichment of the target air-fuel ratio may significantly deteriorate fuel efficiency, and this is prevented by gradually enriching the target air-fuel ratio from the intermediate enrichment value.

The above-mentioned predetermined decrease value and predetermined intermediate value depend on the magnitude of the deviation between the evaluation parameter value Vs and the predetermined discrimination value KV22. It is preferable to set each according to the magnitude of the deviation between the predetermined discrimination value KV23 and the predetermined discrimination value KV23. As a result, the EGR amount is not excessively reduced and corrected, and the target air-fuel ratio is not excessively enriched and corrected, and it is possible to prevent the exhaust gas performance and the fuel consumption from being significantly deteriorated.

[0106] Specific procedures of the control of the above-described combustion variation can easily be the flowchart shown in FIGS. 19 to 22 of the flow chart and reference embodiment 2 shown in FIG. 16 from FIG. 15 of the reference embodiment 1 reference Since it can be understood, the description with the flowchart is omitted. Determining the third embodiment shown in (Third Embodiment) FIG. 24 is a further modification of the second embodiment shown in FIG. 23, the combustion variation in t31 time shown in FIG. 24 (a) is greater Then, the EGR amount is an intermediate decrease with a smaller decrease amount than a predetermined decrease value (as shown in FIG. 24B, a target position value of the EGR valve 45 is a value corresponding to a position closed by ΔPEGR). Value (Δ in the figure
The value is gradually reduced to the value corresponding to PEGRM (see FIG. 24).
(between t31 and t32). The gradual decrease amount of the EGR amount at this time may be set to the same value as the correction amount KEGR of the reference embodiment 2 , or may be set to a value suitable for the third embodiment . Then, after the EGR amount is reduced to the intermediate reduction value (time t32 in FIG. 24B), the EGR amount is reduced to the predetermined reduction value at once. When the EGR amount is reduced to a predetermined decrease value (at time t32), the timer measures the elapsed time and waits for a predetermined period T2. In this case as well, the air-fuel ratio enrichment control is started after waiting for the EGR amount reduction control to stabilize and the EGR amount becoming stable, thereby preventing the air-fuel ratio from varying due to the influence of EGR.

When the predetermined period T2 has elapsed (t33 in FIG. 24)
At the time point), as in the second embodiment , the evaluation parameter value Vs
Is greater than the predetermined determination value KV33, and if it is determined that the combustion fluctuation is not sufficiently suppressed by this determination (Vs> KV33), the air-fuel ratio enrichment control is started. In this air-fuel ratio enrichment control, the target air-fuel ratio AF has an intermediate enrichment value (a value smaller by ΔAFM, which is a smaller enrichment amount than a predetermined enrichment value on the fuel rich side (a value smaller by the correction amount ΔAF). , ΔAFM <ΔAF), the target air-fuel ratio AF is once enriched to an intermediate enrichment value (at time t34 in FIG. 24C), and then is immediately changed to the above-mentioned predetermined enrichment value. It Decreasing amounts dAF of the target air-fuel ratio in this case San
It values may be same for a and used in Remarks Embodiment 2, the
It may be experimentally set to a value compatible with the three examples .

The predetermined decrease value and the predetermined intermediate value are the evaluation parameter value Vs according to the magnitude of the deviation between the evaluation parameter value Vs and the predetermined discrimination value KV32. It is preferable to set them according to the magnitude of the deviation between the predetermined discrimination value KV33 and the predetermined discrimination value KV33. As a result, the EGR amount is not excessively reduced and corrected, and the target air-fuel ratio is not excessively enriched and corrected, and it is possible to prevent the exhaust gas performance and the fuel consumption from being significantly deteriorated.

The specific procedure of controlling the combustion fluctuation of the third embodiment will be described with reference to the flow charts shown in FIGS. 15 to 16 of the reference embodiment 1 and the flow charts shown in FIGS. 19 to 22 of the reference embodiment 2 . Since it can be easily understood, description with the flowchart is omitted. Although various embodiments of the present invention have been described above, various other modes of controlling combustion fluctuation according to the present invention are conceivable. For example, FIG.
It is also possible to combine the EGR reduction control shown in FIG. 24 and the air-fuel ratio enrichment control shown in FIG.

Further, although the air-fuel ratio enrichment means described above enriches the air-fuel ratio by changing the opening degree of the air bypass valve, it can be enriched by changing the fuel injection amount.

[0111]

As described in the foregoing, according to the combustion change control system for an internal combustion engine of the present invention, to detect the combustion fluctuation of the internal combustion engine by the combustion variation detecting means, and calculating an evaluation parameter value related to the combustion variation, When the evaluation parameter value is equal to or more than a predetermined value by the determination means, it is determined that the combustion is deteriorated, the exhaust gas recirculation device controls the recirculation amount of the exhaust gas recirculated from the exhaust system to the intake system, and the exhaust gas recirculation amount correction means controls the recirculation amount. When the determination means determines that the combustion has deteriorated, the exhaust gas recirculation amount is reduced to a predetermined reduction value, and the air-fuel ratio changing means starts the reduction of the exhaust gas recirculation amount by the exhaust gas recirculation amount correcting means, and then a predetermined period of time elapses. Change the target air-fuel ratio to the specified enrichment value on the fuel rich side
In addition, the exhaust gas recirculation amount correction means is based on the determination means.
If it is determined that combustion has deteriorated, the exhaust gas recirculation amount
Temporarily changed to an intermediate decrease value with a smaller decrease amount even with a constant decrease value
However, the exhaust gas recirculation amount decreases until the intermediate reduction value is reached.
Exhaust gas from the intermediate reduction value to the specified reduction value
Since it is set to be different from the reduction rate of the engine recirculation amount, the EGR amount adjustment and the air-fuel ratio adjustment are combined with respect to the engine combustion fluctuations to have a large influence on the combustion deterioration.
By first reducing the GR amount and quickly reducing the deterioration of combustion, by delaying for a predetermined period to enrich the air-fuel ratio,
It is possible to effectively prevent misfire and engine stall, and prevent deterioration of drivability and deterioration of exhaust gas characteristics.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an EGR valve position related to an EGR amount and a cylinder pressure fluctuation rate related to combustion fluctuation.

FIG. 2 is a schematic configuration diagram showing an embodiment of an engine control device according to the present invention.

FIG. 3 is a vertical cross-sectional view of a cylinder injection gasoline engine according to an embodiment.

FIG. 4 is a fuel injection control map that is defined according to the engine in-cylinder average effective pressure Pe and the engine speed Ne, and shows the late injection lean operation range, the early injection lean operation range, the early injection stoichio feedback operation range, etc. is there.

FIG. 5 is a perspective view of a combustion chamber showing a fuel injection form in the latter injection mode.

FIG. 6 is a perspective view of a combustion chamber showing a fuel injection form in the first-term injection mode.

FIG. 7 is a flowchart of a combustion variation detection interrupt routine showing a procedure for calculating a combustion variation evaluation parameter value.

FIG. 8 illustrates a procedure of combustion fluctuation control according to the first embodiment.
It is a flow chart of a combustion fluctuation control routine.

9 is executed in step S30 of FIG. 8 and EG
8 is a flowchart of an EGR correction amount calculation routine for explaining a procedure for calculating an R correction amount.

10 is the rest of the flowchart of the EGR correction amount calculation routine that follows the flowchart of FIG.

FIG. 11 is a flowchart of an EGR valve drive routine showing an EGR valve drive procedure.

FIG. 12 is a part of a flowchart of an EGR / air-fuel ratio control routine, which is executed in step S50 of FIG. 8 and shows a control procedure of the EGR amount and the air-fuel ratio when the state where the combustion fluctuation is large continues.

13 is the rest of the flowchart of the EGR / air-fuel ratio control routine that follows the flowchart of FIG.

FIG. 14 is a flow chart of an ABV valve drive routine showing an ABV valve drive procedure.

FIG. 15 is a part of a flowchart of a combustion fluctuation control routine for explaining a procedure of combustion fluctuation control of the second embodiment.

16 is a flowchart of the remaining part of the combustion fluctuation control routine following the flowchart of FIG.

FIG. 17 is a combustion fluctuation evaluation parameter value Vi and an EGR valve target position value PEG in the combustion fluctuation control of the second embodiment.
6 is a graph showing the relationship between R 1 and the target air-fuel ratio AF over time.

FIG. 18 is a combustion fluctuation evaluation parameter value Vi and EGR valve target position value PEG in combustion fluctuation control of the third embodiment.
6 is a graph showing the relationship between R 1 and the target air-fuel ratio AF over time.

FIG. 19 is a part of a flowchart of a combustion fluctuation control routine for explaining the procedure of the combustion fluctuation control of the third embodiment.

20 is another part of the flowchart of the combustion fluctuation control routine following the flowchart of FIG.

FIG. 21 is another part of the flowchart of the combustion fluctuation control routine following the flowchart of FIG. 20.

22 is the rest of the flowchart of the combustion fluctuation control routine that follows the flowchart of FIG.

FIG. 23 is a combustion fluctuation evaluation parameter value Vi and an EGR valve target position value PEG in the combustion fluctuation control of the fourth embodiment.
6 is a graph showing the relationship between R 1 and the target air-fuel ratio AF over time.

FIG. 24 is a combustion fluctuation evaluation parameter value Vi and an EGR valve target position value PEG in the combustion fluctuation control of the fifth embodiment.
6 is a graph showing the relationship between R 1 and the target air-fuel ratio AF over time.

[Explanation of symbols]

1 engine 4 Fuel injection valve 5 Combustion chamber 17 Crank angle sensor (engine speed detection means) 24 Idle control valve 27 ABV valve 44 EGR pipe 45 EGR valve 70 Electronic Control Unit (ECU)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02D 45/00 301 F02D 45/00 301F 345 345A 368 368S 376 376C F02M 25/07 550 F02M 25/07 550F 550G 550L 550R (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 21/08 301 F02D 41/14 310 F02D 41/22 305 F02D 43/00 301 F02D 45/00 301 F02D 45/00 345 F02D 45/00 368 F02D 45 / 00 376 F02M 25/07 550

Claims (21)

(57) [Claims] 1. A detecting combustion fluctuation of the internal combustion engine, a combustion variation detecting means for calculating an evaluation parameter value related to the combustion variation, a determination unit and the combustion deterioration when the evaluation parameter value is equal to or larger than a predetermined value, An exhaust gas recirculation device that controls the recirculation amount of exhaust gas that is recirculated from the exhaust system to the intake system, and an exhaust gas recirculation amount correction device that reduces the exhaust gas recirculation amount to a predetermined reduction value when the deterioration of combustion is determined by the determination device. When, and a fuel ratio changing means for changing the target air-fuel ratio to a predetermined enrichment value of the fuel-rich side from the reduction of the exhaust gas recirculation amount according to the exhaust gas recirculation amount compensation means is started after a predetermined period of time, The exhaust gas recirculation amount correction means uses the determination means to burn the fuel.
When it is determined that the combustion has deteriorated, the exhaust gas recirculation amount is reduced by the above
Change to an intermediate decrease value that decreases less than a small value,
Exhaust gas recirculation amount reduction rate until reaching the intermediate reduction value
Is the exhaust gas from the intermediate reduction value to the predetermined reduction value.
A combustion fluctuation control device for an internal combustion engine , characterized in that it is different from the reduction rate of the recirculation amount . 2. The combustion fluctuation control device for an internal combustion engine according to claim 1, wherein the predetermined decrease value is set to a value such that a specific exhaust gas component in the exhaust gas does not deteriorate more than a predetermined amount. 3. The combustion fluctuation control device for an internal combustion engine according to claim 1, wherein the predetermined enrichment value is set to a value at which fuel consumption does not deteriorate more than a predetermined value. 4. The combustion fluctuation control device for an internal combustion engine according to claim 1, wherein the predetermined decrease value is set to a value at which the exhaust gas recirculation device is fully closed. 5. The deviation between the evaluation parameter value obtained by the combustion fluctuation detecting means and the predetermined value is obtained, and when the deviation exceeds a determination threshold, the exhaust gas recirculation amount correcting means determines the exhaust gas recirculation amount. The combustion fluctuation control device for an internal combustion engine according to claim 1 , wherein the combustion fluctuation control device reduces the intermediate decrease value. 6. The combustion fluctuation control device for an internal combustion engine according to claim 5 , wherein the intermediate reduction value is corrected according to the magnitude of the deviation. 7. After reducing the exhaust gas recirculation amount to the intermediate reduction value, characterized in that gradually decreased in the predetermined reduced value, the combustion fluctuation of the internal combustion engine according to any one of claims 1 to 6 Control device. Wherein said predetermined time period, characterized in that the exhaust gas recirculation amount from the decrease is started in the exhaust gas recirculation amount is the period until a predetermined reduced value, claims 1 to 7
5. A combustion fluctuation control device for an internal combustion engine according to any one of 1. 9. The air-fuel ratio changing means, when the evaluation parameter value obtained by the combustion fluctuation detecting means exceeds a second predetermined value after a predetermined period has elapsed since the reduction of the exhaust gas recirculation amount was started, and changes the target air-fuel ratio of the fuel rich side to the predetermined enrichment value, the combustion variation control device for an internal combustion engine according to any of claims 1 to 8. Wherein said air-fuel ratio changing means may gradually change the target air-fuel ratio to the predetermined enrichment value, the combustion variation control device for an internal combustion engine according to any one of claims 1 to 9. 11. The air-fuel ratio changing means changes a target air-fuel ratio to the predetermined enrichment value.
10. A combustion fluctuation control device for an internal combustion engine according to any one of 9 to 9 . 12. The air-fuel ratio changing means is characterized in that the target air-fuel ratio than the predetermined thickening value temporarily changed to an intermediate thickening value of the fuel lean side, according to any one of claims 1 to 11 Fluctuation control device for internal combustion engine of the above. 13. The air-fuel ratio changing means obtains a second deviation between the evaluation parameter value obtained by the combustion variation detecting means after the elapse of the predetermined period and the second predetermined value, and the second deviation is the second discrimination value. 13. The combustion fluctuation control device for an internal combustion engine according to claim 12 , wherein the target air-fuel ratio is changed to the intermediate enrichment value when the threshold value is exceeded. 14. The intermediate thickening value, characterized in that it is corrected in accordance with the magnitude of the second difference, claim 13
A combustion fluctuation control device for an internal combustion engine as described above. 15. After the target air-fuel ratio is changed to the intermediate thickening value, characterized in that said to gradually change to a predetermined enrichment value, combustion in the internal combustion engine of any of claims 12 to 14 Fluctuation control device. 16. A failure determination means for determining that the exhaust gas recirculation device is in failure is provided when the evaluation parameter exceeds the predetermined value even after the predetermined period has elapsed. The combustion fluctuation control device for an internal combustion engine according to any one of claims 1 to 15 . 17. The exhaust gas recirculation device comprises an exhaust passage for recirculating exhaust gas from an exhaust system to an intake system, and an exhaust recirculation valve arranged in the middle of the exhaust passage for adjusting the exhaust gas recirculation amount, an average value of the evaluation parameter values that the combustion variation detecting means obtains, and corrects the valve opening reference position of the EGR valve on the basis of the average value, wherein any one of claims 1 to 16 Fluctuation control device for internal combustion engine of the above. 18. The method according to claim 1, further comprising stop means for stopping the reduction of the exhaust gas recirculation amount by the exhaust gas recirculation amount correction means when the evaluation parameter value is equal to or less than the predetermined value. 18. A combustion fluctuation control device for an internal combustion engine according to any one of 17 . 19. When the evaluation parameter value is less than the predetermined value, characterized in that it comprises a second stop means for stopping the change of the target air-fuel ratio by said air-fuel ratio changing means, according to claim 1 to 18 5. A combustion fluctuation control device for an internal combustion engine according to any one of 1. 20. When the evaluation parameter value becomes equal to or less than a third predetermined value set to a value smaller than the predetermined value,
The exhaust gas recirculation amount compensation means may increase the exhaust gas recirculation amount, the combustion variation control device for an internal combustion engine according to any one of claims 1 to 19. 21. When the evaluation parameter value is less than or equal to a fourth predetermined value set to a value smaller than the predetermined value,
The air-fuel ratio changing means is characterized by changing gradually the target air-fuel ratio to a value of the fuel lean side, claims 1 to 20
5. A combustion fluctuation control device for an internal combustion engine according to any one of 1.