JPH11200926A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate exhaust oxygen concentration in each cylinder from an output of one oxygen concentration sensor arranged on collected exhaust pipes of an engine. SOLUTION: When every cylinder fuel injection amount control is necessary, a fuel injection amount of the specific cylinder is increased (step 104). EGR is cut, and waste gate valve is fully opened (step 105). The timing Ta is sensed where the fluctuation of exhaust oxygen concentration caused by increasing the fuel injection amount of the specific cylinder is sensed by an oxygen concentration sensor (step 106). Afterward, an output of the oxygen concentration sensor is read (step 108). Corresponding relation between a weight factor (flow amount ratios of the cylinders) and a crank angle is corrected based on the timing Ta. The exhaust oxygen concentration in each cylinder is calculated from the weight factor and the output of the oxygen concentration sensor (step 109). The fuel injection amounts of the cylinders are so corrected as to obtain the same exhaust oxygen density in all the cylinders, based on the calculated exhaust oxygen concentration in each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine having a function of detecting an exhaust oxygen concentration of each cylinder of the internal combustion engine and correcting a fuel injection amount of each cylinder.

[0002]

2. Description of the Related Art In this type of fuel injection control device,
If one oxygen concentration sensor is installed for each cylinder, the cost increases. Therefore, as shown in JP-A-59-101562, one oxygen concentration sensor is provided in a common exhaust pipe of an internal combustion engine. The delay time from the reference timing to the exhaust gas of each cylinder reaching the oxygen concentration sensor is obtained in advance according to the operating state, and the exhaust oxygen concentration for each cylinder is detected from the output of one oxygen concentration sensor based on the delay time. Then, it has been proposed to perform feedback control on the target value.

However, the exhaust gas passing through the collective exhaust pipe of the internal combustion engine is mixed due to the shape of the exhaust pipe, the overlap of the exhaust valve opening timing of each cylinder, and the like. If an attempt is made to detect the concentration with one oxygen concentration sensor, the output of the oxygen concentration sensor will always be an output obtained by mixing the exhaust oxygen concentration of all cylinders,
It is impossible to detect the exhaust oxygen concentration of one cylinder independently. Therefore, it is not possible to accurately detect the exhaust oxygen concentration for each cylinder, and it is difficult to accurately control the exhaust oxygen concentration of each cylinder to a target value.

[0004] In order to solve this problem, Japanese Patent Laid-Open Publication No.
In Japanese Patent Application Publication No. 80040, a model that simulates the behavior of an exhaust system is constructed by regarding the output of an oxygen concentration sensor as a weighted average value obtained by multiplying the combustion history of each cylinder by a predetermined weighting coefficient, and constructs a model for simulating the exhaust oxygen A technique has been proposed in which the concentration is observed by an observer, and the exhaust oxygen concentration for each cylinder is estimated based on the output of the observer, thereby feedback-controlling the exhaust oxygen concentration for each cylinder to a target value.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 5-180 is disclosed.
In Japanese Patent No. 040, the timing at which the exhaust gas of each cylinder is detected by the oxygen concentration sensor is determined according to the engine speed and the load. However, the timing of detection by the oxygen concentration sensor changes due to individual differences and aging of the oxygen concentration sensor, the resistance of the exhaust turbine of the supercharger, etc., so the detection timing is determined according to the engine speed and load. Then, the exhaust oxygen concentration for each cylinder is accurately separated,
Difficult to extract.

The present invention has been made in view of such circumstances, and accordingly, has as its object to accurately estimate the exhaust oxygen concentration for each cylinder from the output of one oxygen concentration sensor installed in a collective exhaust pipe. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can perform fuel injection control for each cylinder with high accuracy.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection control apparatus for an internal combustion engine, comprising: an output of an oxygen concentration sensor installed in a common exhaust pipe; The oxygen concentration is multiplied by a predetermined weighting factor (corresponding to the flow rate ratio of each cylinder) to be regarded as a weighted average exhaust gas oxygen concentration. From the output of this oxygen concentration sensor, the exhaust gas oxygen concentration for each cylinder is determined in consideration of the weighting coefficient. It is estimated by another exhaust oxygen concentration estimating means. At this time, the weighting factor is determined by the weighting factor determining means according to the crank angle at the time of detecting the exhaust oxygen concentration, but when it is determined from the output of the oxygen concentration sensor that the weighting factor is not appropriate (that is, the fuel injection amount for each cylinder). If it is determined that the variation is large), the correspondence between the weight coefficient and the crank angle is corrected by the correction control means. Thus, even if the timing at which the exhaust oxygen concentration of each cylinder is detected by the oxygen concentration sensor changes, the correspondence between the weight coefficient (flow rate ratio of each cylinder) and the crank angle is corrected accordingly. The exhaust oxygen concentration for each cylinder can be accurately estimated from the output of one oxygen concentration sensor installed in the exhaust pipe, and the fuel injection control for each cylinder can be accurately performed.

Here, when correcting the correspondence between the weight coefficient and the crank angle, the fuel injection amount of the specific cylinder is increased or decreased, and the exhaust oxygen concentration generated by the increased or decreased amount is specified. The timing at which the change in the angle is detected by the oxygen concentration sensor may be detected by the crank angle, and the correspondence between the weight coefficient and the crank angle may be corrected based on the detection result. In this case, by increasing or decreasing the fuel injection amount of the specific cylinder, it is possible to accurately detect the delay time until the exhaust oxygen concentration of the specific cylinder is detected,
From this detection result, a weight coefficient that accurately reflects the flow rate ratio of each cylinder can be obtained.

In this case, when increasing or decreasing the fuel injection amount of the specific cylinder, the fuel injection amounts of the cylinders other than the specific cylinder are changed so that the total fuel injection amount per cycle does not change. The correction may be made. By doing so, it is possible to suppress fluctuations in the output of the internal combustion engine when the fuel injection amount of the specific cylinder is increased or decreased, and to maintain good drivability.

Alternatively, when the fuel injection amount of a specific cylinder is increased, the fuel injection timing of the specific cylinder may be retarded. With this configuration, an increase in the output due to an increase in the fuel injection amount of the specific cylinder can be suppressed by retarding the fuel injection timing, and a torque difference between the cylinders can be prevented. Fluctuations can be suppressed. As a result, it is possible to prevent a difference in the exhaust valve opening time of each cylinder from occurring, suppress a change in the flow rate ratio of each cylinder, and improve the estimation accuracy of the exhaust oxygen concentration for each cylinder.

Further, when the fuel injection amount of the specific cylinder is increased, the increased amount of fuel is post-injected in the expansion stroke of the specific cylinder to thereby increase the fuel injection amount of the specific cylinder. May be increased. As described above, if the increased amount of fuel is post-injected and burned in the expansion stroke of the specific cylinder, the increase in the torque of the specific cylinder can be reduced as compared with the case where the main injection amount of the specific cylinder is increased. ,
The torque difference between the cylinders can be reduced.

Further, in the internal combustion engine having the exhaust gas recirculation device, the flow rate ratio of each cylinder fluctuates due to the variation of the exhaust gas recirculation rate for each cylinder. When increasing or decreasing the amount of exhaust gas, it is preferable to stop the exhaust gas recirculation by the exhaust gas recirculation device. In this way, the exhaust oxygen concentration for each cylinder can be accurately estimated without being affected by the exhaust gas recirculation.

When the present invention is applied to an internal combustion engine provided with a supercharging device with a waste gate valve, when increasing or decreasing the fuel injection amount of a specific cylinder, it is possible to reduce the waste amount. It is preferable to open the gate valve. In this way, when the wastegate valve is opened, much of the exhaust gas that has been stirred by the exhaust turbine flows to the wastegate, so that the exhaust gas can be less stirred between the cylinders by the exhaust turbine. The exhaust oxygen concentration can be accurately estimated.

In the case where the present invention is applied to an internal combustion engine having a variable geometry turbo,
When increasing or decreasing the fuel injection amount of the specific cylinder, it is preferable to open the guide plate of the variable geometry turbo so as to reduce the exhaust resistance. This can reduce the agitation of the exhaust gas between the cylinders in the variable geometry turbo.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] FIG. 1 shows an embodiment (1) in which the present invention is applied to a diesel engine.
This will be described with reference to FIG. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An intake pipe 14 of a turbocharger 13 (supercharger) is installed in an intake pipe 12 of a diesel engine 11 which is an internal combustion engine. The intake turbine 14 of the turbocharger 13
Exhaust turbine 15 connected to the diesel engine 1
The exhaust turbine 1 is installed in the
5 is driven to rotate by the kinetic energy of the exhaust gas, thereby rotating the intake turbine 14 to generate a supercharging pressure. The collective exhaust pipe 16 is provided with a wastegate 17 that bypasses the upstream side and the downstream side of the exhaust turbine 15, and the flow rate of exhaust gas passing through the wastegate 17 is controlled by an electromagnetic wastegate valve 18. A limiting current type oxygen concentration sensor 19 for detecting an exhaust oxygen concentration is provided downstream of the waste gate 17 in the collective exhaust pipe 16.

Collective exhaust pipe 1 on the upstream side of exhaust turbine 15
An EGR pipe 20 is connected between the intake pipe 6 and the intake pipe 12 on the downstream side of the intake turbine 14, and an electronically controlled EGR valve 21 is provided in the middle of the EGR pipe 20. Is adjusted, the EGR flow rate passing through the EGR pipe 20 is controlled. An exhaust gas recirculation device (EGR device) 2 is connected between the EGR pipe 20 and the EGR valve 21.
2 are configured. A fuel injection valve 23 is attached to a cylinder head of each cylinder of the diesel engine 11.

The air supercharged by the turbocharger 13 is supplied to the diesel engine 1 via an intake manifold 24.
Each cylinder is sucked. Fuel is injected from the fuel injection valve 23 into the high-temperature air compressed in each cylinder and self-ignites, and the exhaust gas of each cylinder merges into one collective exhaust pipe 16 through the exhaust manifold 25 and is discharged into the atmosphere. Is done.

The operating state of the diesel engine 11 is detected by a crank angle sensor 26, an accelerator sensor 27, a vehicle speed sensor 28, an oxygen concentration sensor 19 and the like, and output signals of these are read into a control circuit 29 for engine control. The control circuit 29 is mainly composed of a microcomputer, and various engine control programs such as the cylinder-by-cylinder injection amount correction program of FIG. 2 are stored in a built-in ROM (storage medium), and these programs are executed. Thus, the fuel injection control, the EGR control, and the control of the waste gate valve 18 are executed. Since the programs other than the cylinder-by-cylinder injection amount correction program of FIG. 2 are the same as the conventional ones, only the cylinder-by-cylinder injection amount correction program of FIG. 2 will be described below.

The cylinder-by-cylinder injection amount correction program of FIG. 2 is executed by the control circuit 29 at every predetermined crank angle or at every predetermined time as follows. First, in step 101, output signals of the accelerator sensor 27, the crank angle sensor 26, and the vehicle speed sensor 28 are read, and in the next step 102, based on the accelerator opening, the engine speed, and the vehicle speed detected from these signals. It is determined whether the current operation state is a steady operation. If it is not a steady operation, it is difficult to detect the exhaust oxygen concentration for each cylinder, so this program is terminated without performing the subsequent processing.

On the other hand, during steady operation, the routine proceeds from step 102 to step 103, where it is determined whether or not cylinder-specific fuel injection amount control is necessary. For example, when the cylinder-by-cylinder fuel injection amount control has never been executed, or when a predetermined integrated traveling distance has been reached since the previous cylinder-by-cylinder fuel injection amount control was executed, or when steady-state operation was performed. When the output change (amplitude) of the oxygen concentration sensor 19 is large, it is determined that the fuel injection amount control for each cylinder is necessary. If it is determined that the cylinder-by-cylinder fuel injection amount control is not necessary, without performing the subsequent processing,
Exit this program.

If it is determined in step 103 that the fuel injection amount control for each cylinder is necessary, the process proceeds to step 104, where the fuel injection amount of a specific cylinder, for example, cylinder # 1, is reduced by a predetermined amount △
The fuel injection amount of the other cylinders # 2 to # 4 is corrected by decreasing the amount by 減 of の Q so that the total fuel injection amount per cycle does not change. This allows
The exhaust oxygen concentration is reduced only in the cylinder # 1, and the engine output is kept constant before and after the correction.

Thereafter, at step 105, the EGR valve 21
, The exhaust gas recirculation is stopped (EGR cut), and the waste gate valve 18 is fully opened, so that the exhaust gas flowing toward the exhaust turbine 15 is discharged to the waste gate 17.
To bypass. Thereafter, at step 106, the output signal of the oxygen concentration sensor 19 is read, and the timing T at which the exhaust oxygen concentration of the cylinder # 1 whose amount has been increased and corrected is best detected.
a (Crank angle) is detected. That is, as shown in FIG. 3, when the fuel injection amount of the cylinder # 1 is increased and corrected, the cylinder # 1 is increased.
Since the amount of oxygen consumed during the combustion of the cylinder increases and the exhaust oxygen concentration of the cylinder # 1 decreases, the output Ta of the oxygen concentration sensor 19 (the detected value of the exhaust oxygen concentration) after the increase correction is the timing Ta. Is detected, the timing Ta at which the exhaust gas of the cylinder # 1 reaches the oxygen concentration sensor 19 is detected.

Then, after the fuel injection amount correction is completed in step 107, the output signal of the oxygen concentration sensor 19 is read again in step 108. The exhaust gas flowing through the collective exhaust pipe 16 is not completely layered due to the influence of the overlap of the exhaust valves between the cylinders, and flows in a state where the exhaust gases of the respective cylinders are mixed. The output (detected value of the exhaust oxygen concentration) is also a value in which the exhaust oxygen concentration of each cylinder is mixed.

Therefore, in the next step 109, the exhaust oxygen concentration for each cylinder is calculated from the output of the oxygen concentration sensor 19 as follows. The output of the oxygen concentration sensor 19 can be regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by the weight coefficient of each cylinder. The weight coefficient of each cylinder is a flow rate ratio of the exhaust gas of each cylinder passing through the oxygen concentration sensor 19 when detecting the exhaust oxygen concentration.

(Output of Oxygen Concentration Sensor 19) = Σ (Exhaust Oxygen Concentration by Cylinder) × (Weight Coefficient) For example, in the case of a four-cylinder engine, it can be specifically expressed by the following determinant.

[0026]

(Equation 1)

In this determinant, the weighting factors An to Dn
Is corrected as follows according to the timing Ta detected in step 106. Timing detected this time Ta (i)
Is compared with the previously detected timing Ta (i-1), and if Ta (i) is later than Ta (i-1), the delay angle ΔTa
Is calculated by the following equation. ΔTa = Ta (i) −Ta (i-1)

Thereafter, the correspondence between the weighting factors An to Dn and the crank angle n is corrected by the following equation. n (current value) = n (previous value) + ΔTa The weight coefficients An to Dn of the above-mentioned determinant are updated, and the output of the oxygen concentration sensor 19 at each crank angle is substituted into the above-mentioned determinant. The exhaust oxygen concentration is calculated. Step 109 for performing the above-described processing plays a role as a cylinder-by-cylinder exhaust oxygen concentration estimating means, a weight coefficient determining means, and a correction control means.

After calculating the exhaust oxygen concentration for each cylinder, step 1
Proceeding to 10, the correction amount of the fuel injection amount for each cylinder is calculated based on the calculated value of the exhaust oxygen concentration for each cylinder so that the exhaust oxygen concentration for all cylinders is the same, and the fuel amount for each cylinder is calculated based on this correction amount. The fuel injection of each cylinder is performed by correcting the injection amount. After this,
In step 111, it is determined whether or not the output amplitude of the oxygen concentration sensor 19 is within a predetermined width. In other words, if the variation in the exhaust oxygen concentration for each cylinder is reduced by the correction of the fuel injection amount for each cylinder performed in step 110, the amplitude of the output of the oxygen concentration sensor 19 is reduced, but the variation in the exhaust oxygen concentration for each cylinder is reduced. Is larger, the oxygen concentration sensor 19
Output amplitude increases. From this relationship, when the amplitude of the output of the oxygen concentration sensor 19 exceeds the predetermined width, it is determined that the variation of the exhaust oxygen concentration for each cylinder exceeds the allowable value, and the process returns to step 101 and repeats the above-described processing.
That is, the process of calculating the exhaust oxygen concentration for each cylinder and correcting the fuel injection amount for each cylinder is repeated so that the exhaust oxygen concentration for all cylinders becomes the same.

If the amplitude of the output of the oxygen concentration sensor 19 falls within a predetermined range due to such correction of the fuel injection amount for each cylinder, it is determined that the variation of the exhaust oxygen concentration for each cylinder is within an allowable value. Proceeding to 112, the detection timing Ta
Is updated to the timing Ta detected in step 106, and the program ends.

According to the embodiment (1) described above,
The fuel injection amount of the specific cylinder is increased and corrected, the timing Ta at which the change in the exhaust oxygen concentration caused by the increased correction is detected by the oxygen concentration sensor 19 is detected by the crank angle, and a weight coefficient (for each cylinder) is determined based on the result. Since the correspondence between the flow rate ratio and the crank angle is corrected, even if the timing at which the exhaust oxygen concentration of each cylinder is detected by the oxygen concentration sensor 19 changes, the weight coefficient and the crank angle are changed accordingly. The correspondence can be accurately corrected, and the exhaust oxygen concentration for each cylinder can be accurately estimated from the output of one oxygen concentration sensor 19 installed in the collective exhaust pipe 16.
The fuel injection control for each cylinder can be accurately performed.

Further, in this embodiment (1), when the fuel injection amount of the specific cylinder is increased and corrected, the fuel injection amounts of the cylinders other than the specific cylinder are changed so that the total fuel injection amount per cycle does not change. Since the decrease correction is performed, the fluctuation of the engine output when the fuel injection amount of the specific cylinder is corrected for the increase can be suppressed, and the drivability can be favorably maintained.

In addition, when the fuel injection amount of a specific cylinder is increased and corrected, EGR cut is performed to prevent fluctuation of the flow rate ratio of each cylinder due to variation of the EGR rate of each cylinder, and the waste gate valve 18 is fully opened. To stop the supercharging and reduce the agitation of the exhaust gas between the cylinders by the exhaust turbine 15.
, The exhaust oxygen concentration for each cylinder can be accurately estimated.

Incidentally, depending on the operating state of the engine 11, there is a possibility that the engine output will change due to EGR cut or supercharging stop (full opening of the waste gate valve 18). For example, when the engine 11 is at a low rotation speed and no supercharging is performed, an increase in the engine output due to the EGR cut may be considered. When the load is high, E
Since the GR rate is low, a decrease in engine output due to supercharging stop may be considered. In such a case, a map of the fuel injection amount for predicting the change of the engine output and correcting the change is stored in advance, and when performing the EGR cut or the supercharging stop, the fuel injection amount of all the cylinders is used by using this map. The amount may be corrected by the same amount to suppress fluctuations in the engine output.

In the present embodiment (1), the fuel injection amount of the specific cylinder is corrected to increase, but may be corrected to decrease. To reduce the fuel injection amount of a specific cylinder,
If the fuel injection amounts of the other cylinders are increased and corrected so that the total fuel injection amount per cycle does not change, the timing Ta at which the output of the oxygen concentration sensor 19 rises most in step 106 is detected. good.

[Embodiment (2)] In the embodiment (1), when the fuel injection amount of the specific cylinder # 1 is increased and corrected, 1
In order not to change the total fuel injection amount per cycle,
Fluctuations in the engine output are suppressed by reducing the fuel injection amounts of the cylinders # 2 to # 4 other than the specific cylinder # 1. However, the embodiment (2) of the present invention shown in FIGS. In step 104a, when the fuel injection amount of the specific cylinder # 1 is increased and corrected, the fluctuation of the engine output is suppressed by retarding the fuel injection timing of the specific cylinder # 1. The other processing is the same as the processing in FIG. 2 described in the embodiment (1), and a description thereof will not be repeated.

As described above, when the fuel injection amount of the specific cylinder # 1 is increased and corrected, if the fuel injection timing of the specific cylinder # 1 is retarded, the fluctuation of the engine output can be suppressed and the torque fluctuation between the cylinders can be suppressed. , The occurrence of a difference in the exhaust valve opening time of each cylinder can be prevented, the change in the flow rate ratio of each cylinder can be suppressed, and the estimation accuracy of the exhaust oxygen concentration for each cylinder can be improved. In addition, vibration due to rotation fluctuation can be reduced.

[Embodiment (3)] In the embodiment (3) of the present invention shown in FIGS. 6 and 7, when the fuel injection amount of the specific cylinder # 1 is increased and corrected, the fuel corresponding to the increased amount is specified. By performing post-injection in the expansion stroke of the cylinder # 1, the specific cylinder # 1
Is increased (step 104b). In this case, the main injection amount of the specific cylinder # 1 is different from the other cylinders # 2 to #
4 is the same as the main injection amount. The other processing is the same as the processing in FIG. 2 described in the embodiment (1), and a description thereof will not be repeated.

As described above, the increased amount of fuel is supplied to the specific cylinder # 1.
When post-injection and combustion are performed in the expansion stroke of the specific cylinder # 1, compared with the case where the main injection amount of the specific cylinder # 1 is increased,
1 can be reduced, the torque difference between the cylinders can be reduced, and the same effect as in the embodiment (2) can be obtained.

[Other Embodiments] In each of the above embodiments (1) to (3), the turbocharger 13 with the waste gate valve 18 is provided, but instead of this, the turbocharger 13 shown in FIG. The geometry turbo 30 may be used. In this case, when increasing (or decreasing) the fuel injection amount of the specific cylinder, the guide plate 31 of the variable geometry turbo 30 may be opened so as to reduce the exhaust resistance. Other controls are performed in the above embodiments (1) to (3).
Any one of the above may be adopted.

Guide plate 31 of variable geometry turbo 30
, The agitation of the exhaust gas between the cylinders by the exhaust turbine 32 in the variable geometry turbo 30 can be reduced, and substantially the same effect as when the waste gate valve 18 is fully opened can be obtained.

In each of the above embodiments (1) to (3), the change in the exhaust oxygen concentration caused by increasing (or decreasing) the fuel injection amount of the specific cylinder # 1 is detected by the oxygen concentration sensor 19 at the timing Ta. Is detected, and the correspondence between the weight coefficient and the crank angle is corrected based on the detection result.
Is monitored, and when it is determined that the weighting coefficient is not appropriate (that is, when it is determined that the variation of the fuel injection amount for each cylinder is large), the correspondence between the weighting coefficient and the crank angle is corrected. Is also good. Hereinafter, this correction method will be specifically described.

Since the output of the oxygen concentration sensor 19 is affected not only by the exhaust oxygen concentration but also by the exhaust pressure and the like, the output of the oxygen concentration sensor 19 always changes even when the exhaust oxygen concentration of each cylinder is constant during steady operation. I do. Therefore, the oxygen concentration sensor 1 in the case where the exhaust oxygen concentration of each cylinder is constant in a steady operation in advance.
Assuming the maximum change width (maximum amplitude) of the output of No. 9 and storing it as an allowable value, it is determined whether or not the amplitude of the output of the oxygen concentration sensor 19 is equal to or less than the allowable value every predetermined time during steady operation. If it exceeds the allowable value, it is determined that the variation in the exhaust oxygen concentration for each cylinder is large, that is, the weight coefficient is not appropriate.

In this case, the correspondence between the weighting factors An to Dn and the crank angle n in the determinant of Equation 1 is corrected as follows. A map of weighting factors An to Dn using n as a parameter is stored in advance in the ROM of the control circuit 29, and first, the exhaust oxygen concentration (actually, the fuel injection amount) of each cylinder is corrected with n = m. As a result, if the output amplitude of the oxygen concentration sensor 19 does not decrease so much,
Assuming that n = m + Δm, the exhaust oxygen concentration of each cylinder is corrected again. As a result, if the amplitude of the output of the oxygen concentration sensor 19 decreases to a value equal to or less than the allowable value, the value is updated as n = m + Δm. Conversely, if the amplitude of the output of the oxygen concentration sensor 19 increases, the same correction is performed with n = m-Δm. Such a correction process is repeated until the amplitude of the output of the oxygen concentration sensor 19 decreases below the allowable value.

Although both the turbocharger 13 and the EGR device 22 are provided in the system configuration example shown in FIG. 1, the present invention is also applied to a system having only one of them or a system having neither of them. It is possible.

In addition, the present invention is not limited to a diesel engine but can be applied to a gasoline engine.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an entire engine control system showing an embodiment (1).

FIG. 2 is a flowchart showing a processing flow of a cylinder-by-cylinder injection amount correction program according to the embodiment (1).

FIG. 3 is a time chart showing how the engine speed and the exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is increased and corrected in the embodiment (1).

FIG. 4 is a flowchart showing a processing flow of a cylinder-by-cylinder injection amount correction program according to the embodiment (2).

FIG. 5 is a time chart showing how the engine speed and the exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is increased and corrected in the embodiment (2).

FIG. 6 is a flowchart showing the flow of processing of a cylinder-by-cylinder injection amount correction program according to the embodiment (3).

FIG. 7 is a time chart showing how the engine speed and the exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is increased and corrected in the embodiment (3).

FIG. 8 is a diagram schematically illustrating a configuration of a variable geometry turbo used in another embodiment.

[Explanation of symbols]

11: diesel engine (internal combustion engine), 12: intake pipe, 13: turbocharger, 15: exhaust turbine, 16:
Collective exhaust pipe, 17: waste gate, 18: waste gate valve, 19: oxygen concentration sensor, 20: EGR
Piping, 21 EGR valve, 22 EGR device, 23 fuel injection valve, 29 control circuit (cylinder-specific exhaust oxygen concentration estimating means, weight coefficient determining means, correction control means), 30 variable geometry turbo, 31 guide Plate, 32 ... exhaust turbine.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/02 380 F02D 41/40 H 41/40 C F02B 37/12 301N

Claims (8)

[Claims] An oxygen concentration sensor installed in a collective exhaust pipe of an internal combustion engine for detecting an exhaust oxygen concentration, and an output of the oxygen concentration sensor is weighted average by multiplying an exhaust oxygen concentration of each cylinder by a predetermined weighting coefficient. Cylinder-specific exhaust oxygen concentration estimating means for assuming exhaust oxygen concentration and estimating cylinder-specific exhaust oxygen concentration in consideration of the weighting coefficient from the output of the oxygen concentration sensor; and a cylinder estimated by the cylinder-specific exhaust oxygen concentration estimating means. A fuel injection control device for an internal combustion engine, comprising: an injection amount correction unit that corrects a fuel injection amount for each cylinder based on another exhaust oxygen concentration, wherein the weight coefficient corresponds to a crank angle at the time of detecting the exhaust oxygen concentration. A fuel injection control device for an internal combustion engine, comprising: a weight coefficient determining means for determining; and a correction control means for correcting the correspondence between the weight coefficient and the crank angle. 2. The correction control means increases or decreases a fuel injection amount of a specific cylinder, and detects, by a crank angle, a timing at which a change in exhaust oxygen concentration caused by the increase or decrease is detected by the oxygen concentration sensor. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the correspondence between the weight coefficient and the crank angle is corrected based on the detection result. 3. The fuel injection amount of a cylinder other than the specific cylinder so that the total fuel injection amount per cycle does not change when increasing or decreasing the fuel injection amount of the specific cylinder. 3. The fuel injection control device for an internal combustion engine according to claim 2, wherein: 4. The fuel for an internal combustion engine according to claim 2, wherein the correction control means delays the fuel injection timing of the specific cylinder when increasing the fuel injection amount of the specific cylinder. Injection control device. 5. When the fuel injection amount of the specific cylinder is increased, the correction control means post-injects the increased amount of fuel in the expansion stroke of the specific cylinder to increase the fuel injection amount of the specific cylinder. 3. The fuel injection control device for an internal combustion engine according to claim 2, wherein the fuel injection amount is increased. 6. An exhaust gas recirculation device, wherein the correction control means stops the exhaust gas recirculation by the exhaust gas recirculation device when increasing or decreasing the fuel injection amount of the specific cylinder. A fuel injection control device for an internal combustion engine according to any one of claims 2 to 5. 7. A supercharger with a waste gate valve, wherein the correction control means opens the waste gate valve when increasing or decreasing the fuel injection amount of the specific cylinder. Item 7. A fuel injection control device for an internal combustion engine according to any one of Items 2 to 6. 8. A variable geometry turbo, wherein the correction control means opens a guide plate of the variable geometry turbo so as to reduce exhaust resistance when increasing or decreasing the fuel injection amount of the specific cylinder. The fuel injection control device for an internal combustion engine according to any one of claims 2 to 6, wherein: