JPH10196381A - Control device of internal combustion engine mounted with variable nozzle type turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent useless reduction in output of a variable nozzle type turbocharger by detecting abnormality of a closed side stick of a variable nozzle on the basis of an increasing tendency of a rate of change of supercharging pressure when an internal combustion engine is put in a prescribed accelerating condition. SOLUTION: An electronic control unit 12 discriminates that an internal combustion engine 10 is accelerating when an increase rate of engine speed of the internal combustion engine 10 exceeds a prescribed value. Next, when judged that engine speed of the internal combustion engine 10 at accelerating time is smaller than prescribed engine speed and throttle opening is larger than prescribed opening, a condition of requiring to detect abnormality of a closed side stick of a turbocharger 56 is practiced. The occurrence of closed side abnormality in the turbocharger 56 of the internal combustion engine 10 is recognized when a rate of change of supercharging pressure is not more than a prescribed value by this practice, and its abnormality is stored in the electronic control unit 12, and a driver of a vehicle is warned of the occurrence of the abnormality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for an internal combustion engine equipped with a variable nozzle type turbocharger.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No.
As disclosed in No. 32, an internal combustion engine equipped with a variable nozzle type turbocharger is known. The variable nozzle type turbocharger includes a variable nozzle for increasing or decreasing an effective area of a flow path inside the exhaust turbine.

[0003] The variable nozzle is controlled so that the effective area of the flow path is reduced in a low load / low rotation region where the flow rate of exhaust gas is small. Further, the variable nozzle is controlled so that the effective area of the flow path becomes large in a high load / high rotation region where the flow rate of the exhaust gas is large. When the variable nozzle is controlled as described above, the variable nozzle type turbocharger can obtain excellent responsiveness and high efficiency in a wide operation region from a low load / low rotation region to a high load / high rotation region. .

In the variable nozzle type turbocharger, an abnormality in which the variable nozzle is fixed in any state, that is, a stick abnormality may occur. The above-described conventional apparatus compares a target angle of a variable nozzle determined according to an operation state of an internal combustion engine with an actual actual angle, and when a difference between the two exceeds a predetermined value, occurrence of a stick abnormality. It has a function to recognize According to the above conventional method,
Stick abnormality of the variable nozzle can be accurately detected.

[0005] Incidentally, the stick abnormality of the variable nozzle is an abnormality in which the variable nozzle sticks in a state of forming a flow path having a small effective area inside the exhaust turbine, that is, a close stick abnormality and the variable nozzle is caused by the exhaust turbine. Can be classified into an abnormality that sticks in a state in which a distribution route having a large effective area is formed inside the inside, that is, an abnormality on the open stick.

[0006] When the close stick abnormality occurs in the variable nozzle, the exhaust pressure tends to be excessive in a region where a large amount of exhaust gas flows. When exhaust pressure becomes excessive, with the the exhaust resistance increases, the intake air amount for the same supercharging pressure P _B is a small amount compared to normal. On the other hand, without directly detecting the intake air amount, in an internal combustion engine for calculating a fuel injection amount based on the supercharging pressure P _B, the fuel injection amount regardless of the closed side stick is calculated in the same amount . For this reason, in such an internal combustion engine, when the close-side stick abnormality occurs, the air-fuel ratio of the air-fuel mixture becomes fuel-rich, and as a result, the exhaust gas temperature may become unduly high.

[0007] The above-mentioned conventional internal combustion engine is provided with a bypass passage for bypassing the exhaust turbine in the exhaust system.
The bypass passage is provided with a bypass valve whose opening is increased when occurrence of a stick abnormality is recognized. For this reason, in the above-mentioned conventional internal combustion engine, even if the variable stick type turbocharger has a closed stick abnormality, the exhaust pressure does not become excessively large due to the abnormality, and the exhaust gas temperature becomes unduly high. Nothing.

[0008] When the open stick abnormality has occurred in the variable nozzle, the exhaust pressure does not become excessive, that is, an unduly high exhaust temperature does not occur even in a region where a large amount of exhaust gas flows. Therefore, when the abnormality of the variable nozzle is the abnormality of the open stick, there is no need to increase the opening degree of the bypass valve. Therefore, when the abnormality of the variable nozzle is the valve opening stick abnormality, it is desirable that the opening degree of the bypass valve is not increased from the viewpoint of preventing the output of the internal combustion engine from being unnecessarily reduced.

[0009]

However, according to the stick abnormality detection method described above, although the occurrence of a stick abnormality can be recognized, the stick abnormality is a closed stick abnormality or an open stick abnormality. Can not be distinguished. For this reason, in the above-mentioned conventional internal combustion engine, when the stick abnormality is recognized, the opening of the bypass valve is uniformly increased. In this regard, the above-described conventional internal combustion engine has a characteristic of unnecessarily reducing the output when an abnormality occurs in the variable nozzle type turbocharger.

The present invention has been made in view of the above points, and provides a control apparatus for an internal combustion engine equipped with a variable nozzle type turbocharger capable of accurately detecting an abnormality in the closing stick of the variable nozzle. This is the first object. In addition, the present invention is equipped with a variable nozzle type turbocharger capable of accurately detecting the closing stick abnormality of the variable nozzle and preventing the mixture from becoming fuel rich when the closing stick abnormality is detected. A second object is to provide a control device for an internal combustion engine that performs the following.

[0011]

A first object of the present invention is to provide a control apparatus for an internal combustion engine equipped with a variable nozzle type turbocharger having a variable nozzle inside an exhaust turbine. Is a predetermined acceleration state, an acceleration state detection means for detecting a change rate of a supercharging pressure of the variable nozzle type turbocharger, and a boost pressure change rate detection means for detecting a change rate of the change rate Change rate increasing / decreasing tendency detecting means, and stick abnormality detecting means for detecting a closing stick abnormality of the variable nozzle based on the increasing / decreasing tendency of the change rate when the internal combustion engine is in the predetermined acceleration state. This is achieved by a control device for an internal combustion engine equipped with a variable nozzle type turbocharger.

In the present invention, in the variable nozzle type turbocharger, an abnormality in which the variable nozzle sticks in a state of forming a flow path with a small effective area inside the exhaust turbine, that is, an abnormality in the closed side stick may occur. is there. Further, in the variable nozzle turbocharger, there may be an abnormality in which the variable nozzle sticks in a state of forming a flow path with a large effective area inside the exhaust turbine, that is, an open stick abnormality.

[0013] If neither the closed stick abnormality nor the open stick abnormality has occurred in the variable nozzle type turbocharger, that is, if the variable nozzle type turbocharger is normal, the supercharge generated by the variable nozzle type turbocharger. The pressure increases efficiently in all rotational ranges as the internal combustion engine is accelerated. In this case, as long as the internal combustion engine maintains a predetermined acceleration state, the rate of change of the supercharging pressure always shows an increasing tendency.

When an open stick abnormality occurs in the variable nozzle type turbocharger, the supercharging pressure generated by the variable nozzle type turbocharger gradually increases in a low rotation speed region as the internal combustion engine is accelerated. However, it rises efficiently in the high rotation region. In this case, although it is slower than the case where the variable nozzle type turbocharger is normal, as long as the internal combustion engine maintains a predetermined acceleration state,
The rate of change of the boost pressure always shows an increasing tendency.

[0015] When the variable stick type turbocharger has a closed stick abnormality, the supercharging pressure generated by the variable nozzle type turbocharger increases efficiently in a low rotation speed region as the internal combustion engine is accelerated. I do. However, in a high rotation region where a large amount of exhaust gas is generated,
The turbo efficiency of the variable nozzle type turbocharger is remarkably deteriorated, and the increasing tendency of the supercharging pressure becomes extremely moderate. For this reason, in such a situation, the change rate of the supercharging pressure tends to decrease even though the internal combustion engine maintains the predetermined acceleration state. In the present invention, when the internal combustion engine maintains a predetermined acceleration state, and the above-described decreasing tendency appears in the change rate of the supercharging pressure, the closing stick is generated in the variable nozzle type turbocharger. Is determined to be.

In the present invention, the change rate of the supercharging pressure detected by the supercharging pressure change rate detecting means is a value corresponding to a change amount of the supercharging pressure per unit time and a unit of the engine speed. It includes both values corresponding to the change amount of the supercharging pressure per change amount. A second object of the present invention is to provide a control apparatus for an internal combustion engine equipped with a variable nozzle type turbocharger according to the first aspect, wherein the magnitude of the supercharging pressure is reflected. A variable nozzle turbocharger comprising: a fuel injection amount calculating unit for calculating a fuel injection amount; and an injection amount reducing unit for reducing the fuel injection amount when a close stick abnormality of the variable nozzle is detected. This is achieved by a control device for an internal combustion engine.

In the present invention, the amount of fuel injected into the internal combustion engine reflects the supercharging pressure. That is, the amount of air drawn into the internal combustion engine increases as the supercharging pressure increases, and decreases as the supercharging pressure decreases.
In the present invention, the supercharging pressure is reflected in the fuel injection amount so that a predetermined air-fuel ratio is realized with respect to the intake air amount thus changed according to the supercharging pressure.

When a close stick error occurs in the variable nozzle type turbocharger, the exhaust pressure becomes higher than when the variable nozzle type turbocharger operates normally.
When the exhaust pressure becomes high, the exhaust resistance increases, and the intake air amount for the same supercharging pressure becomes smaller than that in the normal case.
For this reason, when the same amount of fuel is injected into the internal combustion engine as in the normal state when the close stick abnormality occurs, excess fuel is injected with respect to the intake air amount, and the fuel is supplied to the internal combustion engine. The resulting mixture becomes fuel-rich. In the present invention, the fuel injection amount is reduced in such a case.
For this reason, even if the close-side stick abnormality occurs in the variable nozzle turbocharger, the mixture supplied to the internal combustion engine does not become unduly fuel-rich.

[0019]

FIG. 1 is a system configuration diagram of an internal combustion engine 10 equipped with an exhaust gas recirculation device according to a first embodiment of the present invention. In the present embodiment, the internal combustion engine 10
Is an electronic control unit 12 (hereinafter, referred to as ECU 12)
Is controlled by

The internal combustion engine 10 has a cylinder block 14. A water jacket 16 is formed in the wall of the cylinder block 14. The piston 18, the connecting rod 20, and the crankshaft 22 are housed inside the cylinder block 14.

A water temperature sensor 24 for detecting the temperature of the cooling water flowing inside the water jacket 16 and a crank angle sensor 26 for detecting the rotation angle of the crankshaft 22 are provided on the wall surface of the cylinder block 14. Have been. The output signal of the water temperature sensor 24 and the output signal of the crank angle sensor 26 are both supplied to the ECU 12. The ECU 12 detects the temperature THW of the cooling water and the crank angle CA based on these output signals.

An oil pan 28 is fixed below the cylinder block 14. Engine oil 30 is stored inside the oil pan 28. A cylinder head 32 is fixed to an upper portion of the cylinder block 14. A main combustion chamber 33 is formed between the cylinder head 32 and the piston 18. Inside the cylinder head 32, an intake port 34, a sub-combustion chamber 36, and an exhaust port 38 communicating with the main combustion chamber 33 are formed.

The cylinder head 36 is provided with a fuel injection valve 40 whose tip is exposed to the auxiliary combustion chamber 36 and a glow plug 42 whose tip is similarly exposed to the auxiliary combustion chamber 36. The cylinder head 36 is provided with an intake valve (not shown) for opening and closing the intake port 34 and an exhaust valve 44 for opening and closing the exhaust port 38.

A fuel injection pump 46 is connected to the fuel injection valve 40 via a fuel pipe (not shown). The fuel injection pump 46 is a pump that operates using the output torque of the internal combustion engine 10 as a driving force, and supplies high-pressure fuel to fuel injection valves disposed in each cylinder of the internal combustion engine 10 at appropriate timing. The fuel injection valves disposed in the respective cylinders, when receiving a supply of high-pressure fuel from the fuel pump 46,
Fuel is injected into the sub-combustion chamber 36. Fuel pump 46
Has a built-in NE sensor 48 that detects the rotational speed NE of the internal combustion engine 10. The output signal of the NE sensor 48 is E
It is supplied to the CU 12. The ECU 12 detects the engine speed NE based on the output signal of the NE sensor 48.

An intake passage 50 communicates with an intake port 34 of the internal combustion engine 10. The intake passage 50, the internal pressure of the intake passage 50 (hereinafter, referred to as supercharging pressure P _B) boost pressure sensor 52 for detecting the, and the temperature of the intake air flowing through the intake passage 50, i.e., the intake air temperature THA An intake air temperature sensor 54 for detecting is provided. The output signal of the supercharging pressure sensor 52 and the output signal of the intake air temperature sensor 54 are both EC
U12. ECU12, based on these output signals, for detecting the supercharging pressure P _B and the intake air temperature THA.

A compressor 58 of a variable nozzle type turbocharger 56 (hereinafter, simply referred to as a turbocharger) communicates with the intake passage 50. Turbocharger 5
An air filter (not shown) communicates with the compressor 58 of No. 6. The turbocharger 56 is connected to the internal combustion engine 10.
During the operation of, the air filtered by the air filter is supercharged from the compressor 58 to the intake passage 50. Compressor 58
Has a wastegate valve 60 incorporated therein.
Waist gate valve 60 is opened when the internal pressure of the compressor 58 exceeds a predetermined value, excessive supercharging pressure P _B can be prevented.

An exhaust passage 62 communicates with the exhaust port 38 of the internal combustion engine 10. An exhaust turbine 64 of a turbocharger 56 communicates with the exhaust passage 62. Further, a catalytic converter and a muffler (not shown) communicate with the exhaust turbine 64. The compressor 58 uses the energy of the exhaust gas flowing inside the exhaust turbine 64 to supercharge the air guided from the air filter into the intake passage 50. Exhaust gas flowing from the exhaust passage 62 into the exhaust turbine 64 passes through a flow path formed inside the exhaust turbine 64 toward the catalytic converter.

[0028] If the internal flow path formed of the exhaust turbine 64 has a large effective area, in order to obtain a suitable supercharging pressure P _B by the compressor 58, is needed a large amount of exhaust gas flow rate You. Therefore, when the internal combustion engine 10 is operating at low load and low-speed region, high in order to obtain a sufficient supercharging pressure P _B under the responsiveness, effective exhaust turbine 64 inside the distribution channel area Is desirably small.

On the other hand, when the effective area of the flow path inside the exhaust turbine 64 is small, the exhaust pressure _PEX becomes unduly high in an environment where a large amount of exhaust gas flows into the exhaust turbine 64, that is, the exhaust gas is exhausted. The resistance increases and the internal combustion engine 10
Is realized. Therefore, in a situation where a large amount of exhaust gas is generated, that is, when the internal combustion engine 10 is operating in a high load / high rotation range, the flow path formed inside the exhaust turbine 64 has a large effective area. Is desirable.

The exhaust turbine 64 of the turbocharger 56
Is provided with a plurality of variable nozzles 66 for changing the effective area of the flow path formed therein. These variable nozzles 66 have a vacuum pump (V /
Negative pressure actuators 68 and 70 that operate using a negative pressure supplied from P) as a power source are connected. Negative pressure actuators 68 and 70 change the angle of variable nozzle 66 according to a control signal supplied from ECU 12.

When the internal combustion engine 10 is operating in the low load / low rotation range, the ECU 12 adjusts the angle of the variable nozzle 66 so that the effective area of the flow path formed in the exhaust turbine 64 becomes small. I do. Also, the ECU 12
When the internal combustion engine 10 is operating in a high load / high rotation range, the angle of the variable nozzle 66 is adjusted so that the effective area of the flow path formed in the exhaust turbine 64 is increased. When the variable nozzle 66 is controlled in this way, it is possible to satisfy the above requirement regarding the effective area of the flow path,
The turbocharger 56 can exhibit excellent responsiveness and high supercharging ability in a wide operating range.

An accelerator opening sensor 74 for detecting the opening θ of the accelerator pedal 72 is connected to the ECU 12. The ECU 12 detects the accelerator opening θ based on the output signal of the accelerator opening sensor 74, and further estimates the load of the internal combustion engine 10 based on the accelerator opening θ.

Next, with reference to FIGS. 2 and 3, a description will be given of the relationship between the state and the supercharging pressure P _B of the turbocharger 68. Figure 2 shows the relationship between the engine speed NE is achieved when the internal combustion engine 10 is full acceleration from idling supercharging pressure P _B. The characteristic indicated by the dashed line in FIG.
This shows the characteristics realized when the turbocharger 56 is normal. In addition, the characteristics indicated by the solid line and the broken line in FIG. 2 indicate that the variable stick 66 of the turbocharger 56 has a closed stick abnormality, and
This shows the characteristics realized when an open stick abnormality has occurred.

As described above, the variable nozzle 66 of the turbocharger 56 is controlled according to the operating state of the internal combustion engine 10. When the turbocharger 56 is normal, that is, when the angle of the variable nozzle 66 changes appropriately, FIG.
As indicated by a one-dot chain line in boost pressure P _B from the low rotation region up to the high rotation region, shows a sharp increase over a wide operating range.

On the other hand, when an open stick abnormality occurs in the variable nozzle 66 of the turbocharger 56, characteristics similar to those of a turbocharger having a flow path with a large effective area inside the exhaust turbine can be obtained. In this case, as shown by the broken line in FIG. 2, the supercharging pressure P _B has a small value in the low rotation region and tends to rapidly increase in the high rotation region.

If the variable nozzle 66 of the turbocharger 56 has a stick failure on the closing side, the same characteristics as those of a turbocharger having a flow path with a small effective area inside the exhaust turbine can be obtained. In this case, the supercharging pressure P _B, as shown by a solid line in FIG. 2, shows a sharp increase characteristics in a low rotational region, and shows a very gradual increase in the high rotation region.

FIG. 3 shows the elapsed time t (hereinafter referred to as the full-open acceleration time t) after the full-open acceleration is started when the internal combustion engine 10 is fully accelerated from the idling state, and the supercharging pressure P
_The relationship that is established between the rate of change ΔB of _{B and} ΔNE is shown. The relationship shown by the dashed line, the solid line and the broken line in FIG.
The characteristic realized when the turbocharger 56 is normal, the characteristic realized when the turbocharger 56 has a closed stick abnormality, and the characteristic realized when the turbocharger 56 has an open stick abnormality Represents the characteristics realized. The rate of change ΔP _B /
ΔNE is a variation occurring in the supercharging pressure P _B during the engine speed NE is changed by unit rotation speed corresponds to the slope of the various characteristics curve shown in FIG.

As shown by the one-dot chain line in FIG. 3, when the turbocharger 56 is normal, the rate of change ΔP _B / ΔNE always increases after the full-open acceleration is started. Similarly, if the open-side stick abnormality in the turbocharger 56 has occurred, as shown by the dashed line in FIG. 3, the rate of change [Delta] P _B
/ ΔNE always shows an increasing tendency after the full-open acceleration is started. On the other hand, as shown by the solid line in FIG. 3, when the close-side stick abnormality occurs in the turbocharger 56, the change rate ΔP is maintained for a while after the full-open acceleration is started.
_B / ΔNE shows an increasing trend, but thereafter the rate of change Δ
P _B / ΔNE shows a decreasing tendency.

As described above, in the internal combustion engine 10, the change rate ΔP _B / ΔNE during the full-open acceleration tends to decrease only when the close-side stick abnormality occurs in the turbocharger 56. By the way, the above-mentioned change rate ΔP _B / ΔN
The increase / decrease tendency of E also appears when the internal combustion engine 10 is being accelerated in a region where the wastegate valve 60 does not open, in addition to the case where the internal combustion engine 10 is performing full-open acceleration. Therefore, according to the system of the present embodiment, when the internal combustion engine 10 is in the acceleration state satisfying the above condition, it is determined whether or not the rate of change ΔP _B / ΔNE has a decreasing tendency, so that the turbocharger 56 is determined. It is possible to determine the presence or absence of the close stick abnormality.

FIG. 4 is a flowchart showing an example of a control routine executed by the ECU 12 to determine whether or not the close-side stick abnormality has occurred in the turbocharger 56 by using the above-described method. The control routine shown in FIG. 4 is a periodic interruption routine that is started every predetermined time. FIG.
Is activated, first, the process of step 100 is executed.

In step 100, it is determined whether or not the internal combustion engine 10 is accelerating. In this step 100,
When the rate of increase dNE / dt of the engine speed NE exceeds a predetermined value, it is determined that the internal combustion engine 10 is accelerating. If it is determined in step 100 that the internal combustion engine 10 is not accelerating, the current routine is terminated without any further processing. On the other hand, when it is determined that the internal combustion engine 10 is accelerating, the process of step 102 is executed next.

In step 102, it is determined whether or not the engine speed NE is smaller than the predetermined speed NE ₀ and the throttle opening θ is larger than the predetermined opening θ ₀ .
The predetermined rotation speed NE ₀ is a threshold value for determining whether the waste gate valve 60 is open. In the internal combustion engine 10, when the NE <NE ₀ is not established, it can be determined that there is a possibility that the waste gate valve 60 is open. The predetermined opening degree θ ₀ is a threshold value related to the fuel injection amount. In the internal combustion engine 10, when the throttle opening θ is smaller than the predetermined value θ ₀ , the air-fuel ratio of the air-fuel mixture becomes unduly fuel-rich even if the close-side stick abnormality occurs in the turbocharger 56. Never.

Therefore, when the condition of step 102 is not satisfied, there is a possibility that a state where the close-side stick abnormality can be accurately detected may not be realized, or a state where it is not necessary to detect the close-side stick abnormality. It can be determined that it is formed. In this case, the current routine is terminated without any further processing.
On the other hand, when the condition of step 102 is satisfied, the closing stick abnormality can be accurately detected, and
It can be determined that the state in which the closing stick abnormality needs to be detected is realized. In this case, the process of step 104 is executed next.

In step 104, the change rate ΔP _B / ΔN
It is determined whether E exceeds a predetermined value α. The predetermined value α is a value slightly smaller than the minimum change rate ΔP _B / ΔNE that occurs when the internal combustion engine 10 is in an acceleration state. Therefore, when the rate of change ΔP _B / ΔNE is equal to or smaller than α, that is, when ΔP _B / ΔNE> α is not established, it can be determined that the turbocharger 56 has not been supercharged. In this case, then step 10
6 is executed.

In step 106, it is recognized that an abnormality has occurred in the intake system or the turbocharger system of the internal combustion engine 10. If an abnormality is recognized in step 106,
The abnormality is stored in the ECU 12 and the occurrence of the abnormality is warned to the driver of the vehicle. Present step 106
When this process is completed, the current routine ends.

In the above step 104, ΔP _B / ΔNE>
If it is determined that α is satisfied, then step 108
Is performed. In step 108, the change rate ΔP
_It is determined whether the time differential value d (ΔP _B / ΔNE) / dt of _B / ΔNE is smaller than a predetermined value β. Predetermined value β
Is a value that does not occur during acceleration of the internal combustion engine 10 unless the turbocharger 56 has a closed stick abnormality. Therefore, when the above condition is not satisfied, it can be determined that the close-side stick abnormality has not occurred in the turbocharger 56. In this case, the current routine is terminated without any further processing. On the other hand, when the above condition is satisfied, it can be determined that the close-side stick abnormality has occurred in the turbocharger 56. In this case, the process of step 110 is executed next.

In step 110, the turbocharger 5
It is recognized that a closed stick abnormality has occurred in 6. If an abnormality is recognized in step 110, the ECU 1
The abnormality is stored in the memory 2 and the occurrence of the abnormality is alerted to the driver of the vehicle, and a correction for reducing the fuel injection amount is disclosed as described later. When the process of step 110 ends, the current routine ends.

As described above, according to the system of the present embodiment, when the close-side stick abnormality occurs in the turbocharger 56, the abnormality can be reliably detected by distinguishing it from the open-side stick abnormality. In the above-described embodiment, the supercharging pressure P _B is changed while the engine speed NE changes by the unit speed.
As the rate of change [Delta] P _B / [Delta] NE and the amount of change occurring, tendency of increase or decrease its value, namely, whether the closed side stick abnormality based on the time differential value _{d (ΔP B / ΔNE) /} dt of the change rate [Delta] P _B / [Delta] NE Although the be determined, the present invention is not limited thereto, as the supercharging pressure P change rate the variation [Delta] P _B / Delta] t of _B per unit time, increasing or decreasing trend of the values, i.e., supercharging 2 derivative value d ² ([Delta] P of pressure P _B
B / ΔNE) / dt ² may be used to determine the presence or absence of the closing stick abnormality.

When the close stick abnormality occurs in the turbocharger 56, a higher exhaust pressure is generated in a region where a large amount of exhaust gas flows as compared with a normal state. When the exhaust pressure becomes high, the exhaust resistance increases, so that the intake air amount decreases as compared with normal times. In the internal combustion engine 10, the intake air amount is estimated based on the boost pressure P _B, as appropriate air-fuel ratio is obtained for the estimated amount of intake air,
The fuel injection amount is determined. For this reason, when the closing stick abnormality occurs in the turbocharger 56 and as a result, the amount of intake air is reduced, and if the same amount of fuel is injected as in normal time, the mixing supplied to the internal combustion engine 10 is stopped. Qi becomes fuel rich.

The exhaust gas temperature of the internal combustion engine 10 becomes higher as the mixture supplied to the internal combustion engine 10 becomes richer in fuel.
For this reason, as described above, the fuel-rich mixture is generated by the internal combustion engine 1.
If it is supplied to 0, there is a possibility that the exhaust gas temperature becomes unduly high. Such a disadvantage is caused, for example, by providing a bypass passage that bypasses the exhaust turbine 64 and a bypass control valve that controls the conduction state of the bypass passage in the exhaust system of the internal combustion engine 10, and closing the stick-side abnormality of the turbocharger 56. When is detected, open the bypass valve,
This can be avoided by preventing the generation of high exhaust pressure.

However, in order to realize the above configuration, it is necessary to provide a bypass passage having a diameter enough to accommodate the bypass valve in the exhaust system of the internal combustion engine 10. Therefore, in order to realize such a configuration, it is necessary to secure a sufficient space around the exhaust port 38 of the internal combustion engine 10.

The system according to the present embodiment can prevent the exhaust gas temperature from becoming unduly high when a close-side stick abnormality occurs, without providing the bypass passage as described above. FIG. 5 shows a flowchart of an example of a control routine executed by the ECU 12 to realize such a function. FIG.
Is a periodic interruption routine started every predetermined time. When the routine shown in FIG. 5 is started, first, the process of step 200 is executed.

In step 200, the throttle opening θ and the engine speed N are obtained from various sensors of the internal combustion engine 10.
E, the cooling water temperature THW and boost pressure P _B are read.
In step 202, a fuel injection amount Q to be injected when the turbocharger 56 is normal is calculated based on the various data read in step 200.

In step 204, it is determined whether or not a close stick abnormality has been detected. As a result, if the close stick abnormality is not detected, the current routine is terminated without any further processing. In this case, the fuel injection amount Q obtained in step 202 is supplied to the internal combustion engine 10. On the other hand, if it is determined in step 204 that the close-side stick abnormality has been detected, then the process of step 206 is executed.

In step 206, a process for correcting the fuel injection amount Q to decrease is executed. When the processing of the steps of the present embodiment ends, the current routine ends. in this case,
The amount of fuel supplied to the internal combustion engine 10 is smaller than when the turbocharger 56 is normal. If the fuel injection amount is corrected to be reduced by executing the process of step 206, the air-fuel mixture will not become fuel-rich even if the close-side stick abnormality has occurred in the turbocharger 56. Therefore, according to the system of the present embodiment, it is possible to reliably prevent the exhaust gas temperature from being unduly high even though the bypass passage is not provided.

In the above embodiment, the ECU 12
Executes the processing of steps 100 to 104, whereby the “acceleration state detection means” calculates the rate of change ΔP _B / ΔNE.
The “supercharging pressure change rate detecting means” described above is used to calculate the change rate ΔP _B / Δ
NE differential value d (ΔP _B / ΔNE) / "change rate increases or decreases the tendency detecting means" of claim 1, wherein by dt calculates a is, the claims by performing the processes in steps 108 and 110 1 The described “stick abnormality detecting means” is realized respectively.

In the above embodiment, the ECU 1
2 executes the processing of steps 200 and 202, and the “fuel injection amount calculating means” according to claim 2 executes the processing of steps 204 and 206 to execute “injection of fuel” according to claim 2. Means of weight loss "
Have been realized respectively.

[0058]

As described above, according to the first aspect of the present invention, it is possible to accurately determine whether or not the variable stick type turbocharger has a closed stick abnormality based on the increasing / decreasing tendency of the rate of change of the supercharging pressure. Can be determined.

According to the second aspect of the present invention, when a close stick abnormality occurs in the variable nozzle type turbocharger, that is, the amount of intake air for the same supercharging pressure is smaller than that in normal time. In this case, it is possible to prevent the mixture supplied to the internal combustion engine from becoming extremely rich in fuel.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an internal combustion engine corresponding to one embodiment of the present invention.

2 is a characteristic diagram showing the relationship between the engine rotational speed NE and the supercharge pressure P _B that is implemented by an internal combustion engine shown in FIG.

FIG. 3 is a characteristic diagram showing a relationship between an elapsed time t after the internal combustion engine shown in FIG. 1 has shifted to a fully-open acceleration state and a rate of change ΔP _B / ΔNE of a supercharging pressure P _B.

FIG. 4 is a flowchart of an example of a close stick abnormality detection routine executed in the internal combustion engine shown in FIG. 1;

FIG. 5 is a flowchart of an example of a fuel injection amount calculation routine executed in the internal combustion engine shown in FIG. 1;

[Explanation of symbols]

Reference Signs List 10 internal combustion engine 12 electronic control unit (ECU) 56 variable nozzle type turbocharger (turbocharger) 64 exhaust turbine 66 variable nozzle

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/22 380 F02B 37/12 301Q

Claims (2)

[Claims] 1. A control device for an internal combustion engine equipped with a variable nozzle type turbocharger having a variable nozzle inside an exhaust turbine, comprising: an acceleration state detection means for detecting that the internal combustion engine is in a predetermined acceleration state; A charging pressure change rate detecting means for detecting a charging pressure change rate of the nozzle type turbocharger; a change rate increasing / decreasing tendency detecting means for detecting an increasing / decreasing tendency of the change rate; and the internal combustion engine is in the predetermined acceleration state. And a stick abnormality detecting means for detecting a stick-side abnormality of the variable nozzle based on the increasing / decreasing tendency of the rate of change, a control device for an internal combustion engine equipped with a variable nozzle type turbocharger. 2. A control device for an internal combustion engine equipped with a variable nozzle type turbocharger according to claim 1, wherein a fuel injection amount calculating means for calculating a fuel injection amount so as to reflect the magnitude of the supercharging pressure. A control device for an internal combustion engine equipped with a variable nozzle turbocharger, comprising: an injection amount reduction unit configured to reduce the fuel injection amount when a close stick abnormality of the variable nozzle is detected.