JP2574954B2 - Diagnosis device for correction ventilation system used in internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normal operation of a correction ventilation system such as an EGR system for recirculating exhaust gas of an internal combustion engine to return it to an intake passage and a canister purge system for burning fuel vapor in the internal combustion engine. The present invention relates to a diagnostic device for a correction ventilation system for diagnosing whether or not there is a ventilation.

2. Description of the Related Art As a device for notifying a driver of a malfunction of a correction ventilation system such as an EGR system, for example, as shown in Japanese Patent Application Laid-Open No. 2-75748, an EGR valve is provided in a fuel supply stop state during deceleration. The EGR valve is forcibly opened and closed.
A method for determining whether the R system has failed has been proposed.

In the above prior art, since the EGR valve is opened and closed when the fuel supply is stopped, that is, when the engine brake is applied, the exhaust gas is rapidly sucked into the combustion chamber, and the control effect of the engine brake is reduced. However, there was a problem that was reduced. SUMMARY OF THE INVENTION It is an object of the present invention to provide a diagnostic apparatus which can accurately diagnose a correct ventilation system without impairing the braking effect of an engine brake.

SUMMARY OF THE INVENTION A feature of the present invention is that while the fuel is supplied to the engine, the influence of the correction ventilation system other than the correction ventilation system to be diagnosed is eliminated, and the engine at that time is removed. The diagnosis of the correction ventilation system to be diagnosed is performed based on the change in the physical quantity occurring in the system.

With this configuration, the fuel is supplied to the engine, and the diagnosis is executed while eliminating the influence of the correction ventilation system other than the correction ventilation system to be diagnosed.
Therefore, it is possible to diagnose the correct ventilation system accurately without impairing the braking effect of the engine brake.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of an engine system to which an embodiment of the present invention is applied. An intake pipe 2 and an exhaust pipe 3 of the internal combustion engine 1 are connected by an EGR passage 4 for recirculating exhaust gas, and an EGR valve 5 for adjusting an exhaust gas recirculation amount is provided in the middle of the EGR passage 4. Is provided.
As a passage of the correction ventilation system to the intake pipe 2 other than the EGR passage 4, a canister purge passage 16 for adsorbing gasoline vapor discharged from the fuel tank 19 to the canister 18 and purging the gasoline vapor to the intake pipe 2, There is a blow-by gas passage 20 for returning gas to the intake pipe 2. A canister purge valve 17 is provided in the canister purge passage 16 to adjust a canister purge amount. The blow-by gas passage 20 is provided with a blow-by gas recirculation valve 21 for adjusting the amount of blow-by gas recirculation. Here, blow-by gas is
Depending on the state of the internal combustion engine 1, there are a case where the air is sucked into the intake pipe 2 through the blow-by gas passage 20, and a case where the air is sucked together with the suction air through the air cleaner. The drive of the EGR valve 5 is performed by the control unit 24, and the recirculation amount of the exhaust gas is controlled according to a predetermined procedure. Similarly, the canister purge valve 1
7 and the blow-by gas recirculation valve 21 are also driven by the control unit 24 to control the canister purge amount and the blow-by gas recirculation amount. The control unit 24 operates the internal combustion engine based on signals from a group of sensors such as an intake air amount sensor 6, a throttle opening sensor 7, an intake pipe pressure sensor 8, a crank angle sensor 9, an exhaust gas concentration sensor 10, and a coolant temperature sensor 11. The state is detected, a control amount of the internal combustion engine is calculated in a predetermined procedure based on the information, and each of the valves is controlled based on the calculated amount. Similarly, a fuel injection amount signal is output to the injector 12, an ignition timing signal is output to the ignition device 13, and an idle speed control signal is output to the ISC valve 15. Further, the control unit 24 has a failure diagnosis means for the EGR system for diagnosing whether the EGR system is operating normally. When a failure occurs, the driver is notified by a warning light 22 and the diagnostic information stored in the control unit 24 is read by the external terminal 23. The distributor 19 supplies a voltage to each spark plug. EGR
FIG. 2 shows an example of the intake pipe pressure when the ERG valve is opened and closed at the time of failure diagnosis. This graph shows the EGR at the time of failure diagnosis.
4 shows a change in intake pipe force corresponding to a change in valve opening.
The intake pipe pressure when the opening of the EGR valve is 100% is P
b ₁ , the intake pressure when the opening of the EGE valve is 0% is P
b _0, and the difference between Pb ₁ and Pb ₀ is ΔPb. Then, diagnosis can be performed with the magnitude of ΔPb when in the diagnosis area. 3 and 4 illustrate a self-diagnosis method for an EGR system according to a specific embodiment of the present invention. This is diagnosed by a microcomputer, and is specifically executed in a fixed time process or a main process. In step 31, the operating state of the fuel engine is detected based on the signal from the sensor group, and then in step 32, the operating state is determined in advance in the diagnostic region of the EGR system, that is, the fuel is supplied without the engine brake being operated. Is determined. If it is the diagnostic area, then step 33
Otherwise, abort the diagnosis of the EGR system. In step 33, it is determined whether or not the operation state is a predetermined region where the canister purge amount is small.
If it is an area where the canister purge amount is small, the process proceeds to step 34, otherwise, the diagnosis of the EGR system is stopped. In step 34, it is determined whether or not the operation state is a predetermined region where the blow-by gas recirculation amount is small. If the blow-by gas recirculation amount is small, the process proceeds to step 35, otherwise, the diagnosis of the EGR system is stopped. In step 35, the opening of the ISC valve 15 is fixed at a predetermined opening. In step 36,
The EGR valve 5 is closed and the EGR passage 4 is shut off. When predetermined time T ₁ is elapsed, the intake pipe pressure Pb determined as shown in FIG. 2, and Pb _0. Then step 3
At 9, the EGR valve 5 is opened and the EGR passage 4 is opened. Next When predetermined time T ₂ has elapsed at step 40, the intake pipe pressure Pb measured in step 41, and Pb _1. In step 42, the difference between Pb ₁ and Pb ₀ is set to ΔPb, and in step 43, a predetermined value PT and Δ
Compare Pb. If ΔPb is larger than PT, it is determined in step 44 that the EGR system is normal,
If so, it is determined in step 51 that the EGR system has failed. If a failure is determined, step 5
In step 2, the display device 22 is turned on to notify the driver of the occurrence of the failure. If the diagnostic information is stored in a memory having a backup power supply in the control unit and can be read out at any time by the external terminal 23, it can be used as maintenance information. FIG. 4 shows a diagnostic region of the EGR system according to the embodiment based on FIG. The rotational speed and load (for example, negative pressure, air amount, basic injection amount), which are the operating states of the internal combustion engine, are plotted on the horizontal axis and the vertical axis, respectively, and the area A indicates the operating area of the canister purge system and the blow-by gas recirculation system. , B
The region indicated by indicates the operation region of the EGR system. Then, the shaded portion becomes the diagnosable area of the EGR system. By performing the failure diagnosis of the EGR system according to the above procedure, the EGR system can be operated without impairing the braking effect of the engine brake.
The exhaust gas recirculation amount is reflected in the change in the physical quantity of the engine such as the intake pipe pressure and intake air amount when the valve is opened and closed.
In addition, since the influence of the canister purge amount and the blow-by gas recirculation amount is small, the failure diagnosis of the EGR system can be accurately performed. Next, another embodiment of the present invention will be described with reference to FIG. If it is determined in step 32 that the engine is in the EGR diagnostic region as in the embodiment of FIG. 3, the canister purge valve and the blow-by recirculation valve are forcibly closed in steps 61 and 62 to shut off the ventilation. Thereafter, as in the embodiment of FIG. 3, the EGR valve is opened and closed in steps 35 to 52, and the diagnosis of the EGR valve is executed from the change in the intake pipe pressure. As described above, since the influence of the canister purge amount and the blow-by gas recirculation amount can be eliminated, E can be accurately measured over a wide range.
Diagnosis of the GR system can be performed. In addition to the embodiments of FIGS. 3 and 5 described above, when the EGR failure is diagnosed, the canister purge gas and the blow-by gas are measured by an air flow meter, so that the EGR system failure based on the canister purge and the blow-by gas recirculation is performed. The effect of pressure fluctuation on diagnosis can be eliminated. This will be described with reference to FIGS. 6 and 7 taking a canister purge system as an example. The upstream portion of the throttle valve 7 of the intake pipe 2 and the canister 18
Is connected via a ventilation path 131, and a passage switching valve 132 is provided on the way. At the time of the EGR failure diagnosis, the switching valve 132 is switched to the ventilation path 131 so that a part of the intake air measured by the air flow meter is vented to the canister 18.
The state is switched to the normal state, that is, the path through which the atmosphere is sucked. According to the above method, the accuracy of the failure diagnosis of the EGR system can be improved with a simple structure, and the failure diagnosis area can be widened. In the present embodiment, the failure diagnosis area of the EGR system is determined based on the signals of a group of sensors for detecting the operating state of the internal combustion engine, and the failure diagnosis of the EGR system uses the signal of the intake pipe pressure sensor. Therefore, when these sensor groups are faulty, there is a possibility that a correct diagnosis area determination and fault diagnosis cannot be performed. Further, even when a group of actuators such as an EGR valve, a canister purge valve, and a blow-by gas recirculation valve have failed, the failure diagnosis cannot be performed by the above procedure. Therefore, prior to the failure diagnosis of the EGR system, it is necessary that the sensor group diagnoses the actuator group according to a predetermined procedure and performs the failure diagnosis of the EGR system when there is no failure of the sensor and the actuator. is there.
If any one of the sensors and the actuator has failed, the failure diagnosis of the EGR system is prohibited.
Thereby, erroneous determination due to a failure of the sensor or the actuator can be prevented. As is well known, the self-diagnosis means of the sensor group includes, for example, monitoring of upper and lower limit values, the monitor of a signal change width under specific conditions, and the like. Since there is a monitor of the terminal voltage, it can be realized by using these. When the EGR valve is forcibly opened and closed as shown in FIG. 2 at the time of failure diagnosis of the EGR system, the recirculation amount of the exhaust gas changes rapidly.
Then, when the EGR valve is closed and the amount of recirculation of exhaust gas decreases, the amount of inert gas in the mixture decreases, and the combustion energy of the mixture increases. Further, when the EGR valve is opened and the recirculation amount of the exhaust gas increases, the amount of inert gas in the air-fuel mixture increases, and the combustion energy of the air-fuel mixture decreases. Therefore, at the time of failure diagnosis of the EGR system, abrupt change of the combustion energy of the air-fuel mixture occurs due to forced closing and opening of the EGR valve. This results in fluctuations in the torque generated by the internal combustion engine, which may cause deterioration in drivability such as fluctuations in the number of revolutions. Therefore, in such a case, at the time of failure diagnosis of the EGR system, the ignition timing is advanced or retarded by a predetermined amount in accordance with the timing of forcibly closing and opening the EGR valve or the fluctuation range of the rotation speed. Thereby, rotation fluctuation is suppressed, and deterioration of drivability is prevented. Hereinafter, a method of correcting the torque fluctuation will be described with reference to a flowchart of FIG. FIG. 8 is a flowchart executed at a fixed time or for each angle. In this flowchart, step 101 is the pre-correction ignition timing θ _IGO calculated in the ignition timing control routine. Step 10
In 2 it is diagnosed whether the EGR system is under failure diagnosis,
If the diagnosis is in progress, proceed to step 103, otherwise,
In step 121, θ _{IGO is set} to the ignition timing θ _IG . In step 103, it is determined whether the EGR valve is being opened or closed. If the valve is open, the rotational fluctuation dN /
dt is calculated. In step 112, the advance angle Δθ _AD is calculated, and in step 113, a value obtained by subtracting Δθ _AD from θ _{IGO is} set as the ignition timing θ _IG . If the valve is closed, a rotation fluctuation dN / dt is calculated in step 104. In step 105, the retard amount Δθ _LE is calculated, and in step 106, a value obtained by adding Δθ _LE to θ _IGO is set as the ignition timing θ _IG . According to the above, at the time of failure diagnosis of the EGR system, it is possible to suppress the rotation fluctuation due to a rapid change in the exhaust gas recirculation amount, and thus prevent the drivability from being deteriorated. Further, from the physical quantity of the ventilation of the correction ventilation system including the EGR system sucked into the intake pipe, the EGR
If the failure diagnosis of the EGR system is performed after the physical quantity due to the ventilation of the ventilation system other than the system is subtracted, the influence of the ventilation by the ventilation system other than the EGR system on the failure diagnosis can be eliminated. Hereinafter, the present invention will be described with reference to FIG. 9 using a canister purge system in combination. In step 31, the operating state of the internal combustion engine is detected based on the signal from the sensor group. Next, in step 32, it is determined whether or not the operating state is within a predetermined diagnostic region of the EGR system. If it is in the diagnosis area, the process proceeds to the next step 35, otherwise, the diagnosis of the EGR system is stopped. In step 35, the opening of the ISC valve 15 is fixed at a predetermined opening. In step 36, the EGR valve 5 is closed and the EGR passage 4 is shut off. When predetermined time T ₁ is elapsed in step 37, the intake pipe pressure Pb measured in step 38, and Pb _0. Next, at step 39, E
The GR valve 5 is opened to open the EGR passage 4. Step 4
When predetermined time T ₂ has elapsed at 0, Step 4
The intake pipe pressure Pb is measured at ₁ and is set to Pb1. Next, at step 42, the difference between Pb ₁ and Pb ₀ is set to ΔPb. Negative pressure Pc generated by canister purge in step 141
Is calculated. As a means for calculating this Pc, for example, a characteristic of a change in Pc due to a change in the operating state of the internal combustion engine is stored in advance, and at the time of failure diagnosis of the EGR system, Pc at that time is stored.
There is a method of calculating the value of Pc as needed, and a method of calculating the value of Pc as needed from the canister purge amount at the time of EGR diagnosis, and these methods may employ an appropriate method. The relationship between the purge amount and the negative pressure Pc is shown below. Canister purge amount Gc
Equation 1 is shown in Equation 1, and Equation 2 is shown in Equation 2.

(Equation 1)

(Equation 2) Here, α: flow coefficient A: sectional area g: gravitational acceleration ΔP: atmospheric pressure−ΔPb V: volume R: gas constant T: temperature Next, in step 142, Pc is subtracted from ΔPb to obtain ΔP
b '. At step 143, a predetermined value PT determined from the operating state is compared with ΔPb ′, and if ΔPb ′ is larger than PT, it is determined at step 44 that the EGR system is normal.
If ΔPb 'is equal to or less than PT, EG is determined in steps 51 and 52.
It is determined that the R system has failed. In addition, the present invention
The present invention can be applied to a correction ventilation system other than the EGR system as a diagnosis target. According to the above-described means, a failure diagnosis area can be widened and the accuracy of failure diagnosis of the EGR system can be improved without providing a structurally special device such as an electromagnetic valve in the ventilation system or the like. Although the self-diagnosis device of the EGR system has been described above, when at least one of the correction ventilation systems including the EGR system connected to the intake pipe is provided with a means for forcibly interrupting the ventilation, Of the correction ventilation system can be diagnosed. An embodiment of the present invention will be described below with reference to the flowchart of FIG. In the present embodiment, a case will be described in which a failure diagnosis of a canister purge system is performed among the correction ventilation systems. In step 71 of FIG. 10, the operating state of the internal combustion engine is detected based on the signals from the sensor group in the same manner as in step 31 of FIG. 3, and then in step 72, the diagnostic area of the canister purge system in which the operating state is predetermined is determined. Is determined. If it is in the diagnosis area, the process proceeds to step 73, and if not, the diagnosis is stopped. In steps 73, 74, and 75, the control valves of the EGR system, blow-by gas recirculation system, and ISC system, which are correction ventilation systems other than the diagnosis target, are closed, and the ventilation paths are shut off. Next, in step 76, the canister purge valve is closed, and the passage of the canister purge system to be diagnosed is shut off. The time T predetermined in step 77
₃ When the elapsed to measure the intake pipe pressure Pb at step 78, and Pb _2. Next, at step 79, the canister purge valve is opened to open the passage. When predetermined time T ₄ has elapsed in step 80, to measure the intake pipe pressure Pb at step 81, and Pb _3. Pb in step 82
The difference between ₃ and Pb ₂ is defined as ΔPb, and is compared with a predetermined value PT ₁ determined from the operating state in step 83. Δ in step 83
If Pb is greater than PT _1, it determines canister purge engagement is normal in step 84. If ΔPb is PT ₁ or less at step 83, it determines that the ventilation system of the canister purge system has failed in step 91. If it is determined that a failure has occurred, the display device is turned on in step 92 to notify the driver of the occurrence of the failure. If the diagnostic information is stored in a memory having a backup power supply in the control unit and can be read by the external terminal 23, it can be used as maintenance information. Other correction ventilation systems can be diagnosed by a similar procedure. It goes without saying that the EGR system method shown in FIGS. 3, 5, 8, and 9 can be used in these correction ventilation systems. Finally, although the present invention has been described with the embodiment in which the diagnosis of the control valve is executed, it is also possible to diagnose the blockage of each passage from the operation of the control valve in the same manner. According to the above means, it is possible to diagnose not only the EGR system but also all the correction ventilation systems connected to the intake pipe.

According to the present invention, there is an effect that an accurate diagnosis of the corrected ventilation system can be performed without impairing the braking effect of the engine brake.

[Brief description of the drawings]

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

FIG. 2 shows an example of a change in intake pipe pressure when an EGR valve is opened and closed.

FIG. 3 is a flowchart of one embodiment of the present invention.

FIG. 4 is a diagram showing a failure diagnosis area of the EGR system according to one embodiment of the present invention.

FIG. 5 is a flowchart of another embodiment of the present invention.

FIG. 6 is an overall configuration diagram of another embodiment of the present invention.

FIG. 7 is an enlarged view of a circular broken line portion in FIG. 6;

FIG. 8 is a flowchart of another embodiment of the present invention.

FIG. 9 is a flowchart of another embodiment of the present invention.

FIG. 10 is a flowchart of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Intake pipe, 3 ... Exhaust pipe, 4 ... EGR passage, 5 ... EGR valve, 8 ... Intake pipe pressure sensor, 16 ...
Canister purge passage, 17: canister purge valve, 20: blow-by gas passage, 21: blow-by gas recirculation passage, 24: control unit.

Claims (13)

(57) [Claims] 1. A main ventilation system for sending a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to an internal combustion engine, and a flammable gas to the internal combustion engine separately from the main ventilation system. And / or diagnostic means for diagnosing at least one corrected ventilation system of the corrected ventilation system for delivering at least one non-flammable gas. Operates so as to execute the diagnosis when the fuel is supplied from the fuel supply device and when the correction ventilation system other than the correction ventilation system to be diagnosed is substantially inoperative. Diagnostic apparatus for a corrected ventilation system used in an internal combustion engine that performs the correction. 2. A main ventilation system for sending a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to the internal combustion engine, and a flammable gas to the internal combustion engine separately from the main ventilation system. And / or diagnostic means for diagnosing at least one corrected ventilation system of the corrected ventilation system for delivering at least one non-flammable gas. Operates so as to execute diagnosis in a state where fuel is supplied from the fuel supply device and in an operation state in which a corrected ventilation system other than the corrected ventilation system to be diagnosed is not substantially operated. Diagnostic apparatus for a corrected ventilation system used in an internal combustion engine that performs the correction. 3. A main ventilation system for sending a mixture of air supplied via an air cleaner and fuel supplied via a fuel supply device to the internal combustion engine, and a flammable fuel for the internal combustion engine separately from the main ventilation system. And / or diagnostic means for diagnosing at least one corrected ventilation system of the corrected ventilation system for delivering at least one non-flammable gas. Operates so as to execute the diagnosis when the fuel is supplied from the fuel supply device and when the correction ventilation system other than the correction ventilation system to be diagnosed is forcibly deactivated. A diagnostic device for a correction ventilation system used in an internal combustion engine. 4. A main ventilation system for sending a mixture of air supplied via an air cleaner and fuel supplied via a fuel supply device to the internal combustion engine, and a flammable fuel for the internal combustion engine separately from the main ventilation system. And / or diagnosing the operation of at least two or more correction ventilation systems for delivering a non-flammable gas, a control valve provided in the correction ventilation system, and at least one of the control valves. Diagnostic means, wherein the diagnostic means is in a state in which fuel is supplied from the fuel supply device, and the control valve of the correction ventilation system other than the correction ventilation system to be diagnosed is substantially inoperable. A diagnostic device for a corrected ventilation system for use in an internal combustion engine, wherein the diagnostic device is operable to perform a diagnosis when in a state. 5. A main ventilation system for sending a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to the internal combustion engine, and flammable to the internal combustion engine separately from the main ventilation system. And / or diagnosing the operation of at least two or more correction ventilation systems for delivering a non-flammable gas, a control valve provided in the correction ventilation system, and at least one of the control valves. Operating in a state in which fuel is supplied from the fuel supply device and a control valve of a correction ventilation system other than the correction ventilation system to be diagnosed does not substantially operate. A diagnostic device for a corrected ventilation system for use in an internal combustion engine, wherein the diagnostic device is operable to perform a diagnosis when in a state. 6. A main ventilation system for sending a mixture of air supplied via an air cleaner and fuel supplied via a fuel supply device to the internal combustion engine, and a flammable fuel for the internal combustion engine separately from the main ventilation system. And / or diagnosing the operation of at least two or more correction ventilation systems for delivering a non-flammable gas, a control valve provided in the correction ventilation system, and at least one of the control valves. Diagnostic means, wherein the diagnostic means is in a state where fuel is supplied from the fuel supply device, and forcibly deactivates a control valve of a correction ventilation system other than the correction ventilation system to be diagnosed. A diagnostic apparatus for a corrected ventilation system used in an internal combustion engine, wherein the diagnostic apparatus operates to execute a diagnosis when the state is set. 7. A corrected ventilation system for an internal combustion engine according to claim 1, wherein one of said corrected ventilation systems is an EGR system for recirculating exhaust gas from an exhaust passage of said internal combustion engine to said main ventilation system. System diagnostic device. 8. The EGR system according to claim 1, wherein the correction ventilation system is configured to recirculate exhaust gas from an exhaust passage of the internal combustion engine to the main ventilation system.
A diagnostic apparatus for a correction ventilation system used in an internal combustion engine, which is a canister purge system for adsorbing fuel vapor generated in a fuel tank to a canister and supplying the vapor to the main ventilation system again. 9. A diagnostic system according to claim 1, wherein said diagnosis means detects a change in a physical quantity caused by said internal combustion engine when said correction ventilation system to be diagnosed is operated and when it is not operated. A diagnostic device for a corrected ventilation system used in an internal combustion engine for diagnosing a corrected ventilation system. 10. A correction system according to claim 9, wherein when the diagnosis by said diagnosis means is executed, the torque fluctuation suppressing means for suppressing the torque fluctuation of said internal combustion engine based on the diagnosis is used in the internal combustion engine. Diagnostic device for ventilation system. 11. A diagnosis of a correction ventilation system used in an internal combustion engine, wherein said torque suppression means detects said rotation fluctuation and controls ignition timing so as to suppress said rotation fluctuation. apparatus. 12. A main ventilation system for sending a mixture of air supplied via an air cleaner and fuel supplied via a fuel supply device to an internal combustion engine, and recirculating exhaust gas of the internal combustion engine to the main ventilation system. An EGR system comprising an exhaust gas recirculation passage and an exhaust gas control valve disposed in the exhaust gas recirculation passage, a canister for adsorbing fuel vapor in a fuel tank for storing fuel of the fuel supply device, and a fuel vapor for the canister. A canister purge system including a purge passage to be supplied to the main ventilation system and a purge control valve disposed in the purge passage; and a diagnostic unit for diagnosing the EGR system. When fuel is being supplied from the supply device, and the canister purge system is substantially inactive. When the difference between the intake pipe pressure when the exhaust gas control valve of the EGR system is fully closed and the intake pipe pressure when the exhaust gas control valve is fully opened is equal to or less than a predetermined value, the EGR system is abnormal. A diagnostic device for a corrected ventilation system used in an internal combustion engine, wherein the diagnostic device performs a diagnosis for determining that 13. A main ventilation system for sending a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to an internal combustion engine, and a flammable gas to the internal combustion engine separately from the main ventilation system. And / or diagnostic means for diagnosing at least one corrected ventilation system of the corrected ventilation system for delivering at least one non-flammable gas. In the state where the fuel is supplied from the fuel supply device, from the physical quantity of the internal combustion engine when the corrected ventilation system is operating, the physical quantity obtained by subtracting the physical quantity generated by the operation of the non-diagnostic corrected ventilation system A diagnostic device for a corrected ventilation system used in an internal combustion engine to diagnose a corrected ventilation system to be diagnosed.