JPH09317568A - Abnormality detecting device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a reduction in the output of an engine when an EGR valve is normal by providing an EGR valve opening control part for setting an EGR valve opening based on an operation state and a target EGR rate and a meant for detecting an actual EGR rate and by detecting abnormality of the EGR valve based on the actual EGR rate and the target EGR rate. SOLUTION: When a failure judging signal is input by a failure judging part 17, a fuel injection amount it limited such that the temperature of an EGR valve mounting portion is not above the heat resistance temperature of a mounting member. The pressure in a combustion chamber is measured by a pressure sensor 15 in a cylinder. An actual EGR rate calculating part 16 calculates an actual EGR rate by using the output of the pressure sensor 15 in a cylinder, the output of an engine rotational angle sensor 4, the output of a fuel injection amount setting part 3 and a model which models a combustion phenomenon in the cylinder. The failure judging part 17 compares a target EGR rate with the actual EGR rate to input the difference between them, which prevents a reduction in the output of the engine when an EGR valve is normal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an abnormality detection device for a diesel engine.

[0002]

2. Description of the Related Art As a conventional diesel engine abnormality detecting device, there is, for example, one shown in FIGS.

FIG. 13 shows an outline of the configuration as a first conventional example.

1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor, 8 is a target EGR rate. A setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, and 11 is E
It comprises a GR valve target opening calculation unit.

The fuel pump 2 supplies fuel to the diesel engine according to the output of the fuel injection amount setting unit 3. The fuel injection amount setting unit 3 includes an engine rotation angle sensor 4,
The fuel injection amount is obtained using the output of the accelerator opening sensor 7, the output of the air flow meter 5, and a predetermined map. The target EGR rate setting unit 8 outputs the target EGR rate using the output of the fuel injection amount setting unit 3 and the engine rotation angle sensor 4 and a predetermined map.
In the engine model 9, the fuel injection amount that is the output of the fuel injection amount setting unit 3, the output of the engine rotation angle sensor 4,
The fresh air flow rate, which is the output of the air flow meter 5, the output of the EGR valve target opening calculation unit 11, and the engine dynamics of the engine to be controlled are modeled in advance using an engine model. Calculate the delay coefficient in the system and the cylinder intake gas mass flow rate estimated value. The target EGR flow rate calculation unit 10 calculates the target EGR flow rate from the target EGR rate that is the output of the target EGR rate setting unit 8 and the cylinder intake gas mass flow rate estimated value that is the output of the engine model 9. In the EGR valve target opening calculation unit 11, the target E
Using the target EGR flow rate that is the output of the GR flow rate calculation unit 10, the differential pressure across the EGR valve that is the output of the engine model 9, and the delay coefficient in the intake system, the target opening degree of the EGR valve is calculated,
The opening degree of the EGR valve 6 is controlled. When the EGR valve 6 is stuck open, the amount of fresh air passing through the air flow meter 5 decreases. Therefore, the fuel injection amount set by the fuel injection amount setting unit 3 decreases.

As a second conventional example shown in FIG.
An outline of the configuration of Japanese Patent No. 13134 is shown. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4
Is an engine rotation angle sensor, 5 is an air flow meter, 6
Is an EGR valve, 7 is an accelerator opening sensor, 8 is a target EGR
A rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, 12 is a combustion chamber temperature sensor, 13 is a fail determination unit, and 14 is a fuel injection amount limiting unit. It consists of

The reference numerals 1 to 11 are the same as those in the first conventional example, and the description thereof will be omitted.

The fuel injection amount setting unit 3 outputs the target fuel injection amount to the fuel injection amount limiting unit 14. The fuel injection amount limiting unit 14 outputs the output from the fuel injection amount setting unit 3 to the fuel pump 2 as it is while the fail occurrence signal is not input. The fuel pump 2 supplies fuel to the diesel engine 1 according to the output of the fuel injection amount limiting unit 14.
The combustion chamber temperature sensor 12 measures the temperature in the combustion chamber,
It is output to the fail determination unit 13. The fail determination unit 13 compares a preset abnormality determination temperature with the output of the combustion chamber temperature sensor 12, and if the abnormality determination temperature is exceeded, outputs a failure occurrence signal to the fuel injection amount limiting unit 14. When the fail generation signal is input, the fuel injection amount limiting unit 14 limits the fuel injection amount so that the temperature in the combustion chamber falls to a predetermined value.

[0009]

However, such a conventional diesel engine abnormality detection device has the following problems.

When the fuel injection amount is increased to increase the engine output, the exhaust temperature rises. In a normal state, the EGR valve is fully closed at the time of high output, so that no problem occurs.

However, when the EGR valve is stuck in the open state, high temperature exhaust gas passes through the EGR valve. When a material having low heat resistance such as aluminum is used for the mounting portion of the EGR valve for the purpose of weight reduction and cost reduction, exhaust leakage from the EGR valve occurs.

In the case of the first conventional example, the exhaust temperature exceeds the heat resistance limit of the aluminum member only by reducing the fuel injection amount due to the decrease in the output of the air flow meter. (In the simulation, the temperature rose to about 350 °.) In order to avoid this, the exhaust temperature is the heat-resistant limit of aluminum (about 270 °) even in normal conditions.
The upper limit of the fuel injection amount must be set as follows. However, if the maximum value of the fuel injection amount is set so that the exhaust temperature becomes 270 ° or less, the output of the engine will decrease even when the EGR valve is normal.

Similarly, in the case of the second conventional example, the abnormality judgment temperature must be set below the heat resistant temperature of aluminum.
Therefore, the amount of fuel injection is limited so that the exhaust temperature does not exceed 270 °, so that even when the EGR valve is normal,
The output of the engine decreases.

The present invention has been made by paying attention to such a conventional problem. By calculating an actual EGR rate and making an abnormality determination based on the actual EGR rate, the EGR valve malfunctions without output reduction in a normal state. It is an object of the present invention to provide a diesel engine abnormality detection device that prevents exhaust leakage due to exhaust gas.

[0015]

In order to solve the above problems, the present invention provides a target fuel injection amount setting unit for setting a target fuel injection amount based on the operating state of a diesel engine, and a target fuel injection amount setting unit according to the target fuel injection amount. A fuel pump that supplies fuel to a diesel engine, a target EGR rate setting unit that sets a target EGR rate according to an operating state, an EGR valve, an operating state, and an opening degree of the EGR valve based on the target EGR rate E
EG for diesel engine having GR valve opening control section
The R device has a means for detecting the actual EGR rate, and detects an abnormality of the EGR valve based on the actual EGR rate and the target EGR rate.

Further, a target fuel injection amount setting section for setting a target fuel injection amount based on the operating condition of the diesel engine, a fuel pump for supplying fuel to the diesel engine according to the target fuel injection amount, and a operating condition for the operating condition. Target EGR
EG for a diesel engine having a target EGR rate setting unit for setting a rate, an EGR valve, an operating state, and EGR valve opening control for setting an EGR valve opening based on the target EGR rate
The R device includes an EGR rate estimation unit that calculates an estimated EGR rate from the operating state and a unit that detects an actual EGR rate,
An abnormality of the EGR valve is detected based on the estimated EGR rate and the actual EGR rate.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a first embodiment of the present invention.

First, the structure will be described. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor. , 8 is a target EGR rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, 15 is a cylinder pressure sensor, 16 is an actual EGR rate calculation unit, and 17 is It is composed of a fail judgment unit.

Reference numerals 1, 2, and 4 to 11 are the same as those in the first conventional example, and therefore the description thereof will be omitted.

The fuel injection amount setting unit 3 performs exactly the same processing as the first conventional example when there is no fail determination signal from the fail determination unit 17. When the fail determination signal is input, the fuel injection amount is limited so that the temperature of the EGR valve mounting portion does not exceed the heat resistant temperature of the mounting member.
The in-cylinder pressure sensor 15 measures the pressure in the combustion chamber. Actual EG
In the R ratio calculation unit 16, the output of the in-cylinder pressure sensor 15, the output of the engine rotation angle sensor 4, the output of the fuel injection amount setting unit 3, and a model that models the combustion phenomenon in the cylinder, or is set in advance. Real E using the map
Calculate the GR rate. An embodiment of the actual EGR rate calculator 16 is shown in FIG.

The fail judgment section 17 compares the input target EGR rate with the actual EGR rate, and when the error exceeds a permissible error, a fail judgment signal is sent to the fuel injection amount setting section 3
Enter

A method for obtaining the actual EGR rate by map search will be described below.

First, in FIG. 3, the cylinder pressure, the fuel injection timing, and E
An outline of the relationship between the GR rate and the fuel injection amount is shown. In FIG. 3A, when only the EGR rate is increased at the same fuel injection amount and the same fuel injection timing, the combustion start timing (the time from the intake bottom dead center to the combustion after the fuel injection starts. Combustion start timing = fuel injection timing + Ignition delay time) does not change (T1), and the maximum cylinder pressure decreases (Pmax → Pmax
′), The combustion period becomes long (T2 → T2 ′).

In FIG. 3B, when the fuel injection timing is delayed with the same fuel injection amount and the same EGR rate, the combustion start time is delayed (T1 → T1 ') and the maximum in-cylinder pressure decreases (Pmax).
→ Pmax ′), and the combustion period becomes long (T2 → T2 ′).

In FIG. 3C, when the fuel injection amount is reduced at the same fuel injection timing and the same EGR rate, the combustion start timing does not change (T1) and the maximum cylinder pressure decreases (Pmax →
Pmax ′), and the combustion period becomes short (T2 → T2 ′).

Further, when the engine speed becomes high, even if the fuel injection amount, fuel injection timing and EGR rate are the same, the combustion start timing is relatively delayed, and the combustion period is converted into crank angle, become longer.

A map of the above relationships is shown in FIG.
As shown in FIG.

FIG. 4 is an example of map A and shows the relationship between the combustion start timing and the fuel injection timing. This relationship changes depending on the engine speed.

FIG. 5 is an example of map B and shows the relationship between fuel injection timing, maximum in-cylinder pressure and EGR rate. This relationship is
It changes depending on the engine speed and the fuel injection amount. this is,
This is because, for example, if the fuel injection amount increases, the maximum in-cylinder pressure increases even with the same EGR rate.

Based on the above facts, the actual EGR rate calculator 16
The embodiment will be described with reference to FIG.

The first map selecting section 18 determines which map is to be used to search the fuel injection timing in the map A group from the output of the engine rotation angle sensor 4. Map A group is a map for obtaining the fuel injection timing from the combustion start timing. In the combustion start timing detection unit 19, from the output of the in-cylinder pressure sensor 15 and the output of the engine rotation angle sensor 4,
The combustion start time (T1 in FIG. 3) is calculated. The combustion start timing is the time when a difference of a predetermined value or more occurs with respect to the change in the cylinder pressure when the fuel injection amount is 0. A schematic diagram is shown in FIG. The maximum in-cylinder pressure detection unit 20 determines the maximum in-cylinder pressure (Pmax in FIG. 3) from the output of the in-cylinder pressure sensor 15. The fuel injection timing search unit 21 obtains the fuel injection timing using the map selected by the first map selection unit 18 and the output of the combustion start timing detection unit 19. An example of how to determine the fuel injection timing is shown in FIG.

The second map selecting section 22 determines which map of the map B group should be used to retrieve the actual EGR rate from the output of the fuel injection amount setting section 3 and the output of the engine rotation angle sensor 4. Here, a means for measuring the fuel injection amount may be provided and the measured value may be used.

The map B group is a map set for each engine speed and fuel injection amount, and is a map for obtaining the actual EGR rate from the maximum in-cylinder pressure and fuel injection timing. Map example Figure 5
Shown in In the actual EGR rate search unit 23, the output of the maximum in-cylinder pressure detection unit 20, the output of the fuel injection timing search unit 21, and the second
The actual EGR is performed using the map selected by the map selection unit 22.
Find the rate. An example of how to determine the actual EGR rate is shown in FIG.

FIG. 7 shows the EG used in the fail judgment section 17.
An example of the R rate allowable error is shown.

Generally, when the fuel injection amount is large, that is, when the exhaust temperature is high, the target EGR rate becomes low. Therefore, when the target EGR rate is low, the allowable EGR rate error becomes small. It is said that the fuel will be restricted when a failure is judged, but there is a method of turning on a warning lamp.

When the step motor or the like is used to drive the EGR valve in open loop control, there is a possibility that the EGR valve may not be fixed but may be out of synchronization even if a failure judgment is made. . Therefore, a method of driving the step motor in the closing direction to reconfirm the EGR rate error before limiting the fuel is also conceivable.

FIG. 8 is a diagram showing a second embodiment of the present invention.

First, the structure will be described. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor. , 8 is a target EGR rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, 15 is a cylinder pressure sensor, 16 is an actual EGR rate calculation unit, and 18 is an estimated EGR. A rate calculation unit, which is composed of a fail determination unit 19 and.

The reference numerals 1 to 16 are the same as those in the first embodiment, and the description thereof will be omitted.

In the estimated EGR rate calculation unit 18, the differential pressure across the EGR valve 6, the delay coefficient in the intake system, which is the output from the engine model 9, and the target output from the EGR valve target opening calculation unit 11 are output. The estimated EGR rate is calculated from the EGR valve opening and the output of the air flow meter 5 using the following formula.

The EGR rate is defined by the following equation (1).

[0043]

[Equation 1]

It is assumed that the fresh air sucked into the collector is Qw and the delay due to the collector is a first-order delay, and its time constant is τ.
Then, the fresh air component sucked into the cylinder is Q cyl_w
Is given by the following equation (2).

[0045]

[Equation 2]

The EGR gas Qegr sucked into the collector is given by the following equation (3).

[0047]

(Equation 3)

Similar to the equation (2), the EGR gas component Q cyl_egr sucked into the cylinder is given by the following equation (4).

[0049]

(Equation 4)

Qw: Air flow output Qegr: EGR gas sucked into the collector Q cyl_w: Fresh air component of gas sucked into the cylinder Q cyl_egr: EGR gas component of gas sucked into the cylinder Aegr: EGR valve target opening degree ρegr : EGR gas density ΔP: differential pressure across EGR valve τ: delay coefficient in intake system where ρegr may be a constant or a measured value.

Represents the derivative.

The fail judgment section 19 compares the input estimated EGR rate with the actual EGR rate, and when the error exceeds a permissible error, a fail judgment signal is sent to the fuel injection amount setting section 3
Enter

FIG. 9 shows the EG used in the fail judgment section 19.
An example of the R rate allowable error is shown.

(Third Embodiment) FIG. 10 is a block diagram showing a third embodiment of the present invention.

First, the structure will be described. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor. , 8 is a target EGR rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, 17 is a fail determination unit, 20 is an O ₂ sensor, and 21 is an actual EGR. And a rate calculation unit.

Since the reference numerals 1 to 17 are the same as those in the first embodiment, the description thereof will be omitted.

The O ₂ sensor 20 measures the oxygen concentration in the exhaust gas. In the actual EGR rate calculation unit 21, the cylinder intake gas mass flow rate estimated value which is the output from the engine model 9, the fuel injection amount which is the output of the fuel injection amount setting unit 3, and the exhaust gas which is the output of the O ₂ sensor 20 The actual EGR rate is calculated using the oxygen concentration. The actual EGR rate is calculated by the following formula. Here, the oxygen concentration q1 in the fresh air and the oxygen amount α required to completely burn the unit fuel may be constants using standard values or may be actually measured.

[0058]

(Equation 5)

Qw: flow rate of fresh air component sucked into the cylinder Qegr: flow rate of gas passed through EGR valve sucked into cylinder Q egr_w: flow rate of gas having the same composition as fresh air contained in Qegr Q egr_e: Qegr Qrrl: Gas flow rate other than egr_w Qcrl: Flow rate sucked into cylinder Q4: Flow rate exhausted from cylinder Qf: Fuel injection amount q1: Oxygen concentration in fresh air q3: Oxygen concentration in Qcrl q4: Oxygen concentration in Q4 (Output of O ₂ Sensor) α: Amount of Oxygen Required to Completely Burn Unit Fuel FIG. 11 is a configuration diagram showing a fourth embodiment of the present invention.

First, the structure will be described. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor. , 8 is a target EGR rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, and 18 is an estimated EG.
An R rate calculation unit, 19 is a failure determination unit, 20 is an O ₂ sensor, and 21 is an actual EGR rate calculation unit.

Since the reference numerals 1 to 17 are the same as those in the first embodiment, the description thereof will be omitted. Since 18 is the same as that of the second embodiment, its explanation is omitted. 20-21 is the third
The description is omitted because it is the same as the embodiment.

FIG. 12 is a configuration diagram showing a fifth embodiment of the present invention.

First, the structure will be described. 1 is a diesel engine, 2 is a fuel pump, 3 is a fuel injection amount setting unit, 4 is an engine rotation angle sensor, 5 is an air flow meter, 6 is an EGR valve, 7 is an accelerator opening sensor. , 8 is a target EGR rate setting unit, 9 is an engine model, 10 is a target EGR flow rate calculation unit, 11 is an EGR valve target opening calculation unit, 17 is a fail determination unit, 20 is an O ₂ sensor, and 22 is an actual EGR. And a rate calculation unit.

Since the reference numerals 1 to 20 are the same as those in the third embodiment, the description thereof will be omitted. The O ₂ sensor 20 measures the oxygen concentration of the gas taken in by the cylinder. Real EGR
The rate calculation unit 22 uses the cylinder intake gas mass flow rate estimated value which is the output from the engine model 9 and the oxygen concentration of the gas sucked by the cylinder which is the output of the O ₂ sensor 20,
Calculate the actual EGR rate. The actual EGR rate is calculated by the following formula.
Here, the oxygen concentration q1 in the fresh air may be a constant using a standard value, or may be measured. The EGR rate when the oxygen concentration (q3) of the gas sucked into the cylinder is measured from the above equations (6) and (9),

[0065]

(Equation 6)

The above equation (12) is modified to obtain the following equation (13).

[0067]

(Equation 7)

Qcrl: Flow rate sucked into the cylinder q1: Oxygen concentration in fresh air q3: Oxygen concentration in Qcyl According to the embodiment of the present invention, the output reduction at the time of EGR valve failure is the same as the conventional one, and is normal. It is possible to cope with the failure of the EGR valve without sacrificing the engine output at the time.

[0069]

As described above, according to the present invention, the actual EGR rate is calculated to obtain the target EGR rate,
Alternatively, by comparing with the estimated EGR rate and making a fail judgment based on the error, the output reduction at the time of EGR valve failure is the same as in the conventional case, and it is possible to cope with the EGR valve failure without sacrificing the engine output at the time of normal operation.

In addition to the common effects described above, each embodiment has the following effects.

According to the invention of the second embodiment,
An estimated EGR rate calculator is added to the first embodiment,
The fail judgment unit is changed. Therefore, EG
If the accuracy of the estimated EGR rate when the R valve is normal is high, the allowable error can be reduced as compared with the first embodiment, the accuracy of fail determination can be improved, and the possibility of erroneous failure can be reduced.

According to the invention of the fourth embodiment,
An estimated EGR rate calculator is added to the third embodiment,
The fail judgment unit is changed. Therefore, EGR
If the accuracy of the estimated EGR rate when the valve is normal is high, the allowable error can be reduced as compared with the third embodiment, the accuracy of fail determination can be improved, and the possibility of erroneous failure can be reduced.

According to the invention in the fifth embodiment,
In contrast to the third embodiment, the configuration uses the oxygen concentration of the cylinder intake gas. Therefore, the actual EGR rate can be accurately calculated even when the fuel injection amount is excessively large and complete combustion cannot be achieved even if all the oxygen sucked into the cylinder is consumed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an internal configuration of an actual EGR rate calculation unit according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing the concept of the relationship among in-cylinder pressure, EGR rate, fuel injection timing, and fuel injection amount.

FIG. 4 is a diagram showing an example of a map A for obtaining a fuel injection timing from a combustion start timing.

FIG. 5 is a diagram showing an example of a map B for obtaining an actual EGR rate from the fuel injection timing and the maximum in-cylinder pressure.

FIG. 6 is a schematic diagram showing changes in in-cylinder pressure due to combustion.

FIG. 7 is a diagram showing an example of an EGR rate allowable error used in a fail determination unit.

FIG. 8 is an overall configuration diagram of a second embodiment of the present invention.

FIG. 9 is a diagram showing an example of an EGR rate allowable error used in a fail determination unit.

FIG. 10 is an overall configuration diagram of a third embodiment of the present invention.

FIG. 11 is an overall configuration diagram of a fourth embodiment of the present invention.

FIG. 12 is an overall configuration diagram of a fifth embodiment of the present invention.

FIG. 13 is an overall configuration diagram of a first conventional example.

FIG. 14 is an overall configuration diagram of a second conventional example.

[Explanation of symbols]

1 Diesel engine 2 Fuel pump 3 Fuel injection amount setting unit 4 Engine rotation angle sensor 5 Air flow meter 6 EGR valve 7 Accelerator opening sensor 8 Target EGR rate setting unit 9 Engine model 10 Target EGR flow rate calculation unit 11 EGR valve target opening calculation Part 12 Combustion chamber temperature sensor 13, 17, 19 Fail judgment part 14 Fuel injection amount limit part 15 Cylinder pressure sensor 16, 21, 22 Actual EGR rate calculation part 18 Actual EGR rate estimation part 20 O ₂ sensor

Claims (8)

[Claims] 1. A target fuel injection amount setting unit that sets a target fuel injection amount based on an operating state of a diesel engine, a fuel pump that supplies fuel to the diesel engine according to the target fuel injection amount, and the operating state. Target EGR that sets the target EGR rate according to
An actual EGR rate is detected in a diesel engine EGR device having a rate setting section, an EGR valve, an operating state, and an EGR valve opening degree control section that sets an opening degree of the EGR valve based on a target EGR rate. An abnormality detection device for a diesel engine, comprising means, and detecting an abnormality of the EGR valve based on the actual EGR rate and the target EGR rate. 2. A target fuel injection amount setting unit that sets a target fuel injection amount based on an operating state of a diesel engine, a fuel pump that supplies fuel to the diesel engine according to the target fuel injection amount, and the operating state. Target EGR that sets the target EGR rate according to
In an EGR device for a diesel engine having a rate setting unit, an EGR valve, the operating state, and EGR valve opening control for setting the EGR valve opening based on a target EGR rate, an estimated EGR rate is calculated from the operating state. An abnormality detection device for a diesel engine, comprising: an EGR rate estimating unit for detecting an actual EGR rate; and a means for detecting an actual EGR rate, and detecting an abnormality of the EGR valve based on the estimated EGR rate and the actual EGR rate. 3. The abnormality detecting device for a diesel engine according to claim 1, further comprising means for detecting a pressure in a combustion chamber of the diesel engine and means for detecting an engine rotation speed, and the actual EGR rate. Is an abnormality detection device for a diesel engine, which is calculated from the pressure in the combustion chamber of the diesel engine, the target fuel injection amount, and the engine rotation speed. 4. The diesel engine abnormality detection device according to claim 1, further comprising means for detecting an oxygen concentration of at least one of an air-fuel mixture and an exhaust gas sucked into a cylinder of the diesel engine, A means for detecting the flow rate of gas taken in by the cylinder of the diesel engine is provided, and the actual EGR rate is calculated from the oxygen concentration in the exhaust gas, the flow rate of gas taken in by the cylinder, and the target fuel injection amount. Characteristic diesel engine abnormality detection device. 5. The abnormality detection device for a diesel engine according to claim 2, wherein means for detecting a differential pressure across the EGR valve, means for detecting a delay of an intake system of the diesel engine, and As one, it has a means for detecting the fresh air intake amount, and the EGR rate estimating unit uses the front-rear differential pressure, the delay of the intake system, the EGR valve opening degree, and the fresh air intake amount. Estimated EG
An abnormality detection device for a diesel engine, which calculates an R rate. 6. The diesel engine abnormality detection device according to claim 5, wherein the differential pressure between the front and rear is the target fuel injection amount, the engine rotation speed, the fresh air intake amount, and the EGR valve opening degree. And an abnormality detection device for a diesel engine, which is calculated from an engine model describing dynamic characteristics of the diesel engine. 7. The diesel engine abnormality detection device according to claim 5, wherein the delay of the intake system is caused by the target fuel injection amount, the engine rotation speed, the fresh air intake amount, and the EGR valve opening. And an engine model describing dynamic characteristics of the diesel engine, an abnormality detection device for a diesel engine. 8. The abnormality detection device for a diesel engine according to claim 4, further comprising means for detecting a fresh air intake amount as one of the operating states, wherein a gas flow rate taken by the cylinder is the target. The fuel injection amount, the engine rotation speed, the fresh air intake amount, the EGR
An abnormality detection device for a diesel engine, which is calculated from a valve opening and an engine model describing dynamic characteristics of the diesel engine.