JPH11326136A - Diagnosing device for exhaust gas circulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the diagnosis on an exhaust gas circulating device to be completed surely, by increasing frequency for establishing conditions of permitting diagnosis. SOLUTION: Whether or not a set first diagnosis permitting condition comes into existence in an EGR area in which a vehicle is normally run is discriminated in S1 and, when the condition does not come into existence, a second diagnosis permitting condition which is contingent on a no-load condition and a prescribed number of revolutions is discriminated (S2). When the second condition comes into existence, the circulation of an exhaust gas is forcibly started (S11). A diagnosing device selects reference values for discrimination under each condition (S2 and S10) and proceeds to the diagnoses in and after S3. In S3-S7, the device successively integrates rotation varying parameters related to the circulating rate of the exhaust gas and, after integrating the parameters a prescribed number of times, compares the computed value of the integrated parameter with the reference values for discrimination. When the computed value is smaller than the reference values, the device discriminates that a negative pressure control valve is normal and sets a diagnosis-completion flag (S8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a diagnostic device for self-diagnosing an abnormality of an exhaust gas recirculation device of an internal combustion engine, particularly an abnormality of a negative pressure control valve.

[0002]

2. Description of the Related Art An exhaust gas recirculation device for recirculating a part of exhaust gas to an intake system in order to reduce NOx emitted from an internal combustion engine has been conventionally known. Various types of diagnostic devices for self-diagnosis of whether or not the exhaust gas recirculation device is operating normally have been conventionally proposed.

For example, as an exhaust gas recirculation device, a negative pressure control valve responsive to exhaust pressure is provided, and a control negative pressure generated by the negative pressure control valve is introduced into a negative pressure chamber of the exhaust gas recirculation control valve. Although there is a type in which the exhaust gas recirculation rate is mechanically controlled according to the engine operating conditions, in this type, the diaphragm of the negative pressure control valve is generated in the intake system by opening and closing the atmosphere introduction port. Since the negative pressure is appropriately diluted with the atmosphere and supplied as the above-mentioned control negative pressure, if the diaphragm sticks to the air introduction port, the control negative pressure becomes excessive, and as a result, exhaust gas recirculation occurs. The rate becomes excessively large. Since such an abnormality of the exhaust gas recirculation control system such as an abnormality of the negative pressure control valve appears as an increase in rotation fluctuation due to excessive exhaust gas recirculation or an increase in the combustion period until the in-cylinder pressure becomes maximum, these parameters are detected. Then, by comparing with a predetermined determination reference value, it is possible to diagnose the presence or absence of the abnormality (see, for example,
-288303, JP-A-8-177644 and the like).

[0004]

SUMMARY OF THE INVENTION
It is necessary to perform it while exhaust gas recirculation is actually being performed,
In particular, in order to increase the accuracy of the diagnosis, it is necessary to perform the diagnosis in a region where a large difference occurs in the above-described parameters between normal and abnormal cases. Therefore, the diagnosis is performed on condition that the load and the rotation speed of the engine are within a predetermined diagnosis region which is set in a part of the predetermined EGR region. In order to eliminate the effects of cycle-to-cycle variations and any disturbances,
Since it is necessary to detect a parameter such as a rotation fluctuation parameter, the diagnosis is not completed unless the load and the number of revolutions of the engine remain within the above-mentioned diagnosis area for a certain period.

However, since the diagnosis area must be set in a relatively narrow range as described above, the probability of completing the diagnosis during the actual operation is relatively low. Therefore, the abnormality of the exhaust gas recirculation device may be overlooked for a long time. In addition, for example, at the time of maintenance and inspection, even if an attempt is made to actively diagnose the exhaust gas recirculation device, unless the actual traveling is performed for a long time, the diagnosis is not started, and it is not possible to determine whether there is an abnormality. is there.

[0006]

SUMMARY OF THE INVENTION Accordingly, the invention according to claim 1 is an exhaust gas recirculation control system which is interposed in an exhaust gas recirculation passage communicating an exhaust system and an intake system of an engine and opens in response to a control negative pressure. A valve, and EGR stopping means for shutting off the supply of the control negative pressure based on a control signal so as to stop the exhaust gas recirculation when the load and the rotation speed of the engine are out of the predetermined EGR range. Diagnostic condition determining means for determining whether or not a predetermined diagnostic permission condition including no load and being equal to or higher than a predetermined rotational speed is satisfied, and Diagnostic exhaust gas recirculation executing means for permitting exhaust gas recirculation via the EGR stop means for diagnosis, and parameter detection for detecting engine fluctuation parameters related to the exhaust gas recirculation rate during execution of the diagnostic exhaust gas recirculation. hand When the abnormality determination means for determining the presence or absence of an abnormality of the detected variable parameter is compared with a predetermined determination reference value the vacuum control valve, and comprising the city.

According to a fourth aspect of the present invention, there is provided an exhaust gas recirculation control valve which is interposed in an exhaust gas recirculation passage communicating an exhaust system and an intake system of an engine and is opened in response to a control negative pressure. EGR stop means for shutting off the supply of the control negative pressure based on a control signal so as to stop the exhaust gas recirculation when the rotational speed is out of the predetermined EGR range. In the apparatus, a first determination is made as to whether or not a predetermined first diagnosis permission condition including that a load and a rotation speed of the engine are within a predetermined diagnosis region set in the EGR region is satisfied. Diagnostic condition determining means, second diagnostic condition determining means for determining whether a predetermined second diagnostic permission condition including that the engine is not loaded and the engine speed is equal to or higher than a predetermined rotational speed is satisfied, and When the diagnosis permission condition 2 is satisfied, And diagnostic exhaust gas recirculation execution means for allowing the exhaust gas recirculation via the EGR stop means in order, the first
And a parameter detecting means for detecting a variation parameter of the engine related to the exhaust gas recirculation rate when the second diagnosis permission condition is satisfied, and comparing the detected variation parameter with a predetermined determination reference value to determine whether the negative pressure control valve is abnormal. Abnormality determination means for determining the presence / absence of

That is, when the transmission is in the neutral position,
And with the engine speed increased to a certain speed,
The diagnosis is permitted, and the exhaust gas recirculation is executed. In such a no-load state, exhaust gas recirculation for exhaust gas purification is
Not usually done. That is, it is outside the EGR range, and the EGR
Although the exhaust gas recirculation is stopped by EGR stop means including a cut solenoid valve, etc., the recirculation of exhaust gas is permitted with the permission of the diagnosis. Then, in the state where the exhaust gas recirculation is forcibly performed, a fluctuation parameter related to the exhaust gas recirculation rate is detected, and by comparing this with a determination reference value, it is determined whether there is an abnormality.

As this abnormality, for example, an abnormality of the negative pressure control valve is determined. In other words, in the ninth aspect, the exhaust gas recirculation device includes a negative pressure control valve that generates the control negative pressure by opening and closing the atmosphere introduction port according to the exhaust pressure upstream of the exhaust gas recirculation control valve in the exhaust gas recirculation passage. It is characterized in that an abnormality of the negative pressure control valve is determined as an abnormality of the exhaust gas recirculation device.

[0010] As the variation parameter, for example, a rotation variation parameter indicating the magnitude of the rotation variation of the internal combustion engine is used. In addition, a change in the combustion period until the in-cylinder pressure becomes maximum may be used as the fluctuation parameter.

Such a state where there is no load and the number of rotations is equal to or higher than the predetermined number of revolutions can be reproduced very easily by an operator at the time of maintenance and inspection, for example, so that the diagnosis can be completed quickly and reliably. Then, even when there is no load, by maintaining the rotation speed to some extent, it is possible to avoid the deterioration of drivability and the like due to the exhaust gas recirculation.

One of the conditions for permitting the diagnosis in the no-load state is that, in the inventions according to the second and fifth aspects, the condition that there is no load and the rotation speed is equal to or higher than a predetermined rotation speed is continued for a certain period. .

That is, when no load and a state in which the number of rotations is equal to or higher than a predetermined number of times continues for a predetermined period, forced exhaust gas recirculation is started and diagnosis is performed.

According to the third and sixth aspects of the present invention, one of the no-load diagnosis permission conditions is that an external monitor device is connected to the control unit.

This external monitor device displays, for example, various information of the engine and the presence or absence of an abnormality. The external monitor device is used only when the external monitor device is connected to a control unit at a maintenance shop or the like. Thus, the diagnosis at the time of no load is performed.

According to a fourth aspect of the present invention, a diagnosis under the first diagnosis permission condition during normal operation and a diagnosis under the second diagnosis permission condition at no load can be performed. In the invention according to claim 7, the abnormality determining means has different reference values for the first diagnosis permission condition and the second diagnosis permission condition.

For example, when attention is paid to engine rotation fluctuation as a fluctuation parameter related to the exhaust gas recirculation rate, the air flow rate is smaller in a no-load state than in a normal EGR region, and the rotation fluctuation is relatively small. It will be big,
If the same criterion value is set, there is a possibility of erroneous diagnosis. Therefore, the accuracy of diagnosis can be improved by giving appropriate determination reference values.

[0018]

According to the exhaust gas recirculation device diagnostic apparatus of the present invention, the exhaust gas recirculation device can be forcibly diagnosed in a state where there is no load and the rotation speed is equal to or higher than a predetermined number of revolutions. The presence or absence of an abnormality can be easily confirmed. Therefore, the abnormality of the exhaust gas recirculation device is not overlooked for a long time. Further, at the time of maintenance and inspection, it is possible to easily and surely check for any abnormality without actually running for a long time.

Further, by making the judgment reference value for the diagnosis during normal running different from the judgment reference value for the diagnosis under no load, it is possible to maintain the diagnosis accuracy in each case sufficiently high. it can.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of an exhaust gas recirculation apparatus provided with a diagnostic device according to the present invention. In the figure, reference numeral 1 denotes an internal combustion engine, 2 denotes an intake passage, 3 denotes a throttle valve, and 4 denotes an exhaust passage. An exhaust recirculation passage 5 guides a part of exhaust gas from the exhaust passage 4 to the intake passage 2. Is provided.

The exhaust gas recirculation passage 5 is provided with an exhaust gas recirculation control valve 6 for opening and closing the passage 5. The exhaust gas recirculation control valve 6 has a diaphragm 62 separating a negative pressure chamber 63 and an atmospheric pressure chamber 64, and a valve body 61 attached to the diaphragm 62 opens and closes a communication hole of a valve seat 66. I have. That is, when the control negative pressure introduced into the negative pressure chamber 63 is higher than the set pressure by the spring, the communication hole is opened,
The exhaust gas will recirculate. An EGR orifice 51 is interposed in the exhaust gas recirculation passage 5 upstream of the valve seat 66.

The control negative pressure introduced into the exhaust gas recirculation control valve 6 is generated via a negative pressure control valve 7. The negative pressure control valve 7 has a diaphragm 72 that separates an exhaust pressure chamber 71 and an atmosphere chamber 73, and a valve body 76 provided on the atmosphere chamber 73 side of the diaphragm 72 opens and closes an atmosphere introduction port 75. ing. Note that the diaphragm 72 is provided with the coil spring 7.
4 is urged toward the exhaust pressure chamber 71 side. The air introduction port 75 communicates with the negative pressure passage 8 that extends from the downstream side of the throttle valve 3 of the intake passage 2 to the negative pressure chamber 63. Is introduced, and the control negative pressure introduced into the exhaust gas recirculation control valve 6 is weakened. In addition, the exhaust pressure chamber 71
Is connected to the exhaust gas recirculation control valve 6 downstream of the EGR orifice 51 via the exhaust pressure passage 9, and exhaust pressure between the exhaust gas recirculation control valve 6 and the valve seat 66 is introduced. That is, when the exhaust gas recirculation control valve 6 is opened and the exhaust gas is recirculated, the exhaust pressure introduced into the exhaust pressure chamber 71 decreases, the diaphragm 72 descends, the atmosphere introduction port 75 opens, and the control negative pressure weakens. When the exhaust gas recirculation control valve 6 is closed due to the decrease in the control negative pressure,
The exhaust pressure increases, the atmosphere introduction port 75 closes, and the control negative pressure increases. As a result of such operations being repeated, the exhaust gas recirculation rate is controlled to a predetermined value.

The negative pressure passage 8 is provided with an EGR cut solenoid valve 11 serving as EGR stop means. The EGR cut solenoid valve 11 is formed of a three-way solenoid valve, and can shut off the negative pressure passage 8 and release the negative pressure chamber 63 to the atmosphere passage 10.

The switching of the EGR cut solenoid valve 11 is controlled by a control unit 12 for controlling the entire internal combustion engine 1. The control unit 12 controls the fuel injection, ignition timing, exhaust gas recirculation, etc. of the internal combustion engine 1 and has a function as a diagnostic device for the exhaust gas recirculation device. The self-diagnosis of the exhaust gas recirculation device is performed. The control unit 12 receives input signals of a crank angle sensor 13 for detecting rotation of a crankshaft, an air flow meter 14 for detecting an intake air amount corresponding to a load, and a water temperature sensor 15 for detecting an engine cooling water temperature. I have.

In this embodiment, an external monitor device 16 for diagnosis is detachably connected to the control unit 12 via a connector 17. The external monitor device 16 displays the engine operating conditions at that time, the result of the diagnosis, the completion of the diagnosis, and the like.

FIG. 2 shows an example of an EGR region with respect to the operating conditions of the internal combustion engine 1, that is, the load and the rotation speed. In the illustrated EGR region, the EGR cut solenoid valve 11 is turned off, and the exhaust gas recirculation control is performed. It becomes possible to introduce a control negative pressure to the valve 6, and exhaust gas recirculation is performed. If the load or the rotation speed is outside the EGR range, the EGR cut solenoid valve 11 is turned ON, the negative pressure chamber 63 of the exhaust gas recirculation control valve 6 is released to the atmosphere, and the exhaust gas recirculation control valve 6 is kept closed. . That is, the recirculation of exhaust gas stops. In addition, EGR
Even within the range, the exhaust gas recirculation is stopped by the EGR cut solenoid valve 11 under a predetermined condition in which the exhaust gas recirculation is not preferable, for example, when the cooling water temperature is low.

As shown in the figure, a first diagnostic region is set in the EGR region. In addition, a second diagnostic region indicated by hatching is set in a predetermined rotational speed range with no load. This second diagnostic area is EGR
The EGR cut solenoid valve 11
Exhaust gas recirculation is stopped via.

FIG. 3 is a flow chart showing a flow of diagnosis of the exhaust gas recirculation device executed by the control unit 12. The program shown in this flowchart is started when the engine is started, and is executed on condition that a diagnosis end flag described later is in an initial state. First, in step (abbreviated as S in the figure) 1,
It is determined whether the first diagnosis permission condition is satisfied. The first diagnosis permission condition is a basic condition that the load and rotation speed of the engine are within the first diagnosis region described above, and further, for example, that the water temperature is equal to or higher than a predetermined temperature. Additional conditions have been added. This first
If the diagnosis permission condition is not satisfied, the routine proceeds to step 9, where a second diagnosis permission condition described later is determined.

If the first diagnosis permission condition is satisfied, the routine proceeds to step 2, sets a first reference value "A" as a judgment reference value, and proceeds to diagnosis after step 3. When the first diagnosis permission condition is satisfied, the engine load and the engine speed are, as a matter of course, equal to the aforementioned EG.
It is in the R region, and exhaust gas recirculation is performed.

In step 3, as an engine fluctuation parameter related to the exhaust gas recirculation rate, a rotation fluctuation parameter indicating the magnitude of the rotation fluctuation is measured for each ignition.
Then, the values are sequentially integrated. The rotation fluctuation parameter is given, for example, as a variation in the time required for rotating a predetermined crank angle after ignition, and the like, and becomes larger as the rotation fluctuation is larger. Further, this is correlated with the exhaust gas recirculation rate, and the combustion becomes more unstable as a large amount of exhaust gas recirculation is given. Therefore, if the exhaust gas recirculation rate is large, the rotation fluctuation parameter tends to be large.

In step 5, the number of times of integration of the rotation fluctuation parameter, that is, the number of ignitions after the start of diagnosis is counted.
In step 6, it is determined whether or not the number has reached the specified number of calculations. Then, the integration of the rotation fluctuation parameters is repeated until the specified number of calculations is reached, and when the specified calculation rotation is reached, the process proceeds to step 7 where the calculated parameter calculation value is used as the above-mentioned determination reference value, specifically, the first determination reference value A. Compare with Here, if the parameter calculation value is smaller than the determination reference value A, it is determined that the exhaust gas recirculation device, especially the negative pressure control valve 7 is normal, and a diagnosis end flag indicating the end of diagnosis is set in step 8, and End diagnosis of. An often occurring abnormality of the negative pressure control valve 7 is that the valve body 76 on the diaphragm 72 sticks to the air introduction port 75,
This is a phenomenon in which the introduction of the atmosphere from the atmosphere introduction port 75 becomes impossible. In such an abnormality, the exhaust gas recirculation rate becomes excessively large and the rotation fluctuation parameter increases.

FIG. 4 shows an example of the characteristics of the rotation fluctuation parameters when the negative pressure control valve 7 is normal and abnormal. As shown in the drawing, the rotation fluctuation parameter changes depending on the load, but the diagnosis region is within the range shown as the EGR region. Therefore, even if the variation in a certain range is taken into consideration, it is possible to reliably determine normality and abnormality based on the determination reference value A. The above-described diagnosis based on the first diagnosis permission condition is performed during a normal operation in which the external monitor device 16 is not connected.

On the other hand, if the first diagnosis permission condition is not satisfied in step 1, the process proceeds to step 9 where it is determined whether the second diagnosis permission condition is satisfied. The second diagnosis permission condition may be that the engine operating condition is in the above-described second diagnostic region (no-load, predetermined rotation speed range) and that the operating condition has continued for a certain period of time.
Is connected. That is, the diagnosis permission condition is set when either the state where the transmission is in the neutral state and the so-called idling is continued for a predetermined time or the external monitoring device 16 is connected and the idling is performed in the neutral state of the transmission. It is determined to be established.
As described above, when the second diagnosis permission condition is satisfied, the process proceeds to step 10, sets the second reference value "B" as a determination reference value, and further proceeds to step 11 to recirculate exhaust gas for diagnosis. Start. In other words, the EGR cut solenoid valve 11, which is normally turned on under this operating condition, is turned off to allow the exhaust gas to recirculate. Then, in the state where the exhaust gas recirculation is forcibly executed, the process proceeds to the diagnosis after step 3.

The diagnosis in steps 3 to 8 is basically the same as the processing performed under the above-described first diagnosis permission condition, but in step 7, the integrated parameter operation value is determined by the second determination. It is compared with the reference value B. Here, the criterion value B is set to a value larger than the first criterion value A, as shown in FIG. This is because, as shown in FIG. 4, in the case of no load (NL), the normal E
In consideration of the fact that the air flow rate is smaller than in the GR region and the rotation fluctuation parameter becomes relatively large,
By setting the determination reference value B to a relatively large value in this way, it is possible to reliably determine whether the negative pressure control valve 7 is normal or abnormal, and to eliminate the possibility that the normal one is erroneously determined to be abnormal. When the external monitor device 16 is connected, the result of the diagnosis and the end of the diagnosis based on the setting of the diagnosis end flag are displayed on the external monitor device 16.

Therefore, in this embodiment, for example, at the time of maintenance and inspection, the external monitor device 16 is connected, and the operator can depress the accelerator pedal only slightly to perform the diagnosis without fail and easily check that there is no abnormality. You can check. Even when the external monitor device 16 is not used, if the accelerator pedal is continuously depressed for a certain period of time, the same diagnosis is performed, and it can be easily confirmed that there is no abnormality. Therefore, even if the user uses the vehicle in such a manner as to repeat running for a short time,
This prevents the abnormality of the negative pressure control valve 7 from being overlooked for a long time.

In the above flow chart,
If the parameter operation value is larger than the determination reference value in step 7, the diagnosis end flag is not set. That is,
Although it is determined to be abnormal once, a definite diagnosis of failure is not made, and thereafter, the diagnosis is re-executed every time the diagnosis permission condition is satisfied.

Of course, if it is determined in step 7 that the value is equal to or greater than the determination reference value, it is possible to immediately make a final diagnosis of the abnormality and set the diagnosis end flag.

In this embodiment, the so-called B
Although the PT type exhaust gas recirculation device has been described, the present invention can be similarly applied to a so-called VVT (Venturi Vacuum Transducer) type exhaust gas recirculation device. Further, the present invention can also be applied to an exhaust gas recirculation device that simply performs exhaust gas recirculation on and off.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing the configuration of an exhaust gas recirculation device including a diagnostic device according to the present invention.

FIG. 2 is a characteristic diagram showing an EGR region and first and second diagnosis regions with respect to an engine load and an engine speed.

FIG. 3 is a flowchart showing the flow of a diagnostic process according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a rotation fluctuation parameter and a determination reference value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 6 ... Exhaust gas recirculation control valve 7 ... Negative pressure control valve 11 ... EGR cut solenoid valve 12 ... Control unit 16 ... External monitoring device

Claims (9)

[Claims] An exhaust gas recirculation control valve, which is interposed in an exhaust gas recirculation passage communicating an exhaust system and an intake system of an engine and opens in response to a control negative pressure, has a predetermined engine load and a predetermined engine speed.
To stop exhaust gas recirculation when it is out of the range,
EG that shuts off the supply of the control negative pressure based on the control signal
R stop means, in an exhaust gas recirculation system for an internal combustion engine, comprising: a diagnostic condition determining means for determining whether a predetermined diagnostic permission condition including no load and a predetermined rotational speed or more is satisfied. A diagnostic exhaust gas recirculation executing means for permitting the exhaust gas recirculation through the EGR stop means for diagnosis when the diagnosis permission condition is satisfied, and an engine recirculating ratio related to the exhaust gas recirculation rate during execution of the diagnostic exhaust gas recirculation. Exhaust gas recirculation, comprising: parameter detection means for detecting a fluctuation parameter; and abnormality determination means for comparing the detected fluctuation parameter with a predetermined determination reference value to determine whether or not the exhaust gas recirculation device is abnormal. Device diagnostic device. 2. One of the conditions for permitting diagnosis is as follows:
2. The diagnostic device for an exhaust gas recirculation device according to claim 1, wherein the condition that there is no load and the rotation speed is equal to or higher than a predetermined rotation speed has been continued for a certain period. 3. One of the conditions for permitting diagnosis is as follows:
2. The diagnostic device for an exhaust gas recirculation device according to claim 1, wherein the external monitor device is connected to the control unit. 4. An exhaust gas recirculation control valve, which is interposed in an exhaust gas recirculation passage communicating an exhaust system and an intake system of the engine and is opened in response to a control negative pressure, and an engine load and a rotation speed of a predetermined EGR.
To stop exhaust gas recirculation when it is out of the range,
EG that shuts off the supply of the control negative pressure based on the control signal
R stop means, the first recirculation device for an internal combustion engine, wherein a predetermined first diagnosis permission including a condition that the load and the number of revolutions of the engine are within a predetermined diagnosis region set in the EGR region. First diagnostic condition determining means for determining whether or not the condition is satisfied; and whether or not a predetermined second diagnostic permission condition including that the engine has no load and is at or above a predetermined rotational speed is satisfied. A second diagnosis condition determining means for determining whether or not the EGR is required for the diagnosis when the second diagnosis permission condition is satisfied.
Diagnostic exhaust gas recirculation executing means for permitting exhaust gas recirculation via the stopping means, parameter detecting means for detecting a variation parameter of the engine related to the exhaust gas recirculation rate when the first and second diagnosis permitting conditions are satisfied, An abnormality determining means for comparing the detected variation parameter with a predetermined determination reference value to determine whether there is an abnormality in the exhaust gas recirculation device, and a diagnostic device for the exhaust gas recirculation device. 5. The exhaust gas recirculation device according to claim 4, wherein one of the second diagnosis permission conditions includes a condition in which no load and a predetermined number of revolutions or more continue for a certain period of time. Diagnostic device. 6. The diagnostic device for an exhaust gas recirculation device according to claim 4, wherein one condition of the second diagnostic permission condition is that an external monitor device is connected to a control unit. . 7. The apparatus according to claim 4, wherein said abnormality determination means has different determination reference values for the first diagnosis permission condition and the second diagnosis permission condition, respectively. A diagnostic device for the exhaust gas recirculation device according to the above. 8. The diagnostic device for an exhaust gas recirculation system according to claim 1, wherein a rotation fluctuation parameter indicating a magnitude of rotation fluctuation of the internal combustion engine is used as the fluctuation parameter. 9. The exhaust gas recirculation device includes a negative pressure control valve that generates the control negative pressure by opening and closing an air introduction port in accordance with exhaust pressure upstream of the exhaust gas recirculation control valve in the exhaust gas recirculation passage. And determining whether there is an abnormality in the negative pressure control valve as an abnormality in the exhaust gas recirculation device.
The diagnostic device for an exhaust gas recirculation device according to any one of claims 1 to 8.