JPH0539752A - Diagnostic device for correction ventilating system used for internal combustion system - Google Patents

Abstract

PURPOSE:To provide a diagnostic method for correction ventilating systems including EGR systems transferring air to internal combustion engines, particularly a method for allowing troubleshooting without a loss of the braking effect of an engine brake. CONSTITUTION:When an EGR system 5 is diagnosed, diagnosis is performed when fuel is supplied to an internal combustion engine 1 and canister purge systems 16 through 18 and blow-by gas reflux systems 20 and 21 are virtually in non-operation state. Because troubleshooting is performed while fuel is being supplied, correct diagnosis for a correction ventilating system is carried out without a loss of the braking effect of an engine brake.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normal 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 combusting 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.

2. Description of the Related Art As a device for informing 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 placed in a fuel supply stop state during deceleration. Forcibly opening and closing, and the change in intake pipe pressure due to opening and closing of the EGR valve
It has been proposed to determine if the R system is out of order.

In the above-mentioned prior art, since the EGR valve is opened / closed in the state where the fuel supply is stopped, that is, the engine brake is applied, the exhaust gas is rapidly sucked into the combustion chamber, and the engine brake control effect is obtained. There was a problem that An object of the present invention is to provide a diagnostic device that can accurately diagnose a correction ventilation system without impairing the braking effect of engine braking.

A feature of the present invention is that the engine is being supplied with fuel while the influence of other correction ventilation systems other than the correction ventilation system to be diagnosed is eliminated. The correction ventilation system is to be diagnosed based on the change in the physical quantity that occurs in the above.

According to this structure, the engine is supplied with fuel, and the diagnosis is executed by eliminating the influence of the correction ventilation system other than the correction ventilation system to be diagnosed.
Therefore, it is possible to accurately diagnose the correction ventilation system 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. The intake pipe 2 and the exhaust pipe 3 of the internal combustion engine 1 are connected by an EGR passage 4 in order to recirculate exhaust gas, and an EGR valve 5 for adjusting the exhaust gas recirculation amount is provided in the middle of the EGR passage 4. It 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 into the intake pipe 2, a blow-by passage. There is a blow-by gas passage 20 for returning the gas to the intake pipe 2. A canister purge valve 17 is provided in the canister purge passage 16 and adjusts the canister purge amount. A blow-by gas recirculation valve 21 is provided in the blow-by gas passage 20 to adjust the recirculation amount of the blow-by gas. Here, blow-by gas is
Depending on the state of the internal combustion engine 1, it may be sucked into the intake pipe 2 through the blow-by gas passage 20 or may be sucked together with the intake air through the air cleaner. The EGR valve 5 is driven by the control unit 24, and the recirculation amount of the exhaust gas is controlled according to a predetermined procedure. Also, similarly, the canister purge valve 1
7 and the blow-by gas recirculation valve 21 are also driven by the control unit 24, and the canister purge amount and the blow-by gas recirculation amount are controlled. The control unit 24 operates the internal combustion engine based on signals from a sensor group including 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, a cooling water temperature sensor 11 and the like. The state is detected, the control amount of the internal combustion engine is calculated according to a predetermined procedure based on the information, and the above valves are controlled based on the calculated amount. Similarly, the fuel injection amount signal is output to the injector 12, the ignition timing signal is output to the ignition device 13, and the idle speed control signal is output to the ISC valve 15. Further, the control unit 24 has EGR system failure diagnosis means for diagnosing whether the EGR system is operating normally. When a failure occurs, the driver is notified by the warning light 22 and the diagnostic information stored in the control unit 24 is read by the external terminal 23. Distorbutor 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 / closed during failure diagnosis. This graph shows EGR at the time of failure diagnosis.
The change in the intake pipe force corresponding to the change in the valve opening is shown.
The intake pipe pressure when the EGR valve opening is 100% is P
b ₁ , the intake pressure when the EGE valve opening is 0%, P
b _0, and the difference between Pb ₁ and Pb ₀ is ΔPb. Then, the diagnosis can be performed with the magnitude of ΔPb when it is in the diagnosis area. A self-diagnosis method for an EGR system, which is a specific embodiment of the present invention, will be described with reference to FIGS. This is diagnosed by a microcomputer, and specifically, it is executed in a fixed time process or a main process. In step 31, the operating state of the fuel engine is detected by the signal from the sensor group, and in step 32, the operating state is a predetermined diagnostic region of the EGR system, that is, the fuel is not supplied while the engine brake is not operating. It is determined whether or not it is in the state. If it is in the diagnostic area, then step 33
Otherwise go to EGR system diagnostics. In step 33, it is determined whether or not the operating state is a predetermined region where the canister purge amount is small.
If the canister purge amount is small, the process proceeds to step 34, otherwise, the EGR system diagnosis is stopped. In step 34, it is determined whether or not the operating state is a predetermined region where the blow-by gas recirculation amount is small. If the amount of blow-by gas recirculation 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 to a predetermined opening. In step 36,
The EGR valve 5 is closed and the EGR passage 4 is shut off. After the elapse of a predetermined time T ₁ , the intake pipe pressure Pb is measured as shown in FIG. 2 and set as Pb ₀ . Next step 3
At 9, the EGR valve 5 is opened and the EGR passage 4 is opened. Next, when a predetermined time T ₂ has elapsed in step 40, the intake pipe pressure Pb is measured in step 41 and is set to Pb ₁ . In step 42, the difference between Pb ₁ and Pb ₀ is set to ΔPb, and in step 43, the predetermined value PT and Δ determined from the operating state are set.
Compare Pb. If ΔPb is larger than PT, it is determined in step 44 that the EGR system is normal, and ΔPb is PT.
If the following is true, it is determined in step 51 that the EGR system is out of order. If determined to be a failure, 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 by the external terminal 23 at any time, it can be used as maintenance information. The diagnostic area of the EGR system of the embodiment based on FIG. 3 is shown in FIG. The rotation 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 vertical axis, respectively, and the region A indicates the operating region of the canister purge system and blow-by gas recirculation system. , B
Indicates the operating area of the EGR system. The shaded area is the EGR system diagnosable area. If the failure diagnosis of the EGR system is carried out by the above procedure, the EGR system will not be impaired in braking effect and the EGR system will not be damaged.
The exhaust gas recirculation amount is reflected in the amount of change in the physical quantity of the engine such as the intake pipe pressure and intake air amount when the valve is opened / closed, and diagnosis can be performed.
Moreover, the influence of the canister purge amount and the blow-by gas recirculation amount is small, so that the failure diagnosis of the EGR system can be performed accurately. Next, another embodiment of the present invention will be described with reference to FIG. If it is determined in step 32 that it 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 cut off the ventilation. Thereafter, as in the embodiment of FIG. 3, the EGR valve is opened / closed in steps 35 to 52 to diagnose the EGR valve from the change in the intake pipe pressure. In this way, the influence of the canister purge amount and blow-by gas recirculation amount can be eliminated, so that E can be accurately measured in a wide range.
Fault diagnosis of GR system can be performed. In addition to the embodiments of FIGS. 3 and 5 described above, the EGR system failure based on the canister purge or blow-by gas recirculation is measured by measuring the canister purge gas or blow-by gas with an air flow meter at the time of EGR failure diagnosis. The effect of pressure fluctuations on the diagnosis can be eliminated. This will be described with reference to FIGS. 6 and 7 by taking the canister purge system as an example. The upstream portion of the throttle valve 7 of the intake pipe 2 and the canister 18 are described.
The atmosphere opening port is connected via a ventilation path 131, and a passage switching valve 132 is provided in the middle thereof. Then, at the time of EGR failure diagnosis, the switching valve 132 is switched to the ventilation path 131 so that part of the intake air measured by the air flow meter is vented to the canister 18, and at the time of non-diagnosis,
Switch to the normal state, that is, the passage through which the atmosphere is inhaled. According to the above method, the accuracy of failure diagnosis of the EGR system can be improved with a simple structure, and there is an effect that the failure diagnosis area can be widened. By the way, in the present embodiment, the determination of the failure diagnosis region of the EGR system is performed by the signal of the sensor group that detects the operating state of the internal combustion engine, and the signal of the intake pipe pressure sensor is used in the failure diagnosis of the EGR system. Therefore, when these sensor groups are out of order, there is a possibility that correct diagnosis area determination and failure diagnosis cannot be performed. Further, even when the actuator group such as the EGR valve, the canister purge valve, the blow-by gas recirculation valve, etc. is out of order, the failure diagnosis according to the above procedure cannot be performed. Therefore, prior to the failure diagnosis of the EGR system, it is necessary for the sensor group to perform the diagnosis of the actuator group in a predetermined procedure so as to perform the failure diagnosis of the EGR system when there is no failure of the sensor and the actuator. is there.
If any of the sensors and actuators is out of order, failure diagnosis of the EGR system is prohibited.
This can prevent erroneous determination due to a sensor or actuator failure. The sensor group self-diagnosis means includes, for example, a monitor of upper and lower limit values and a signal change width monitor under a specific condition as well known, and the actuator group self-diagnosis means includes, for example, a drive signal output of a control unit. Since there is a terminal voltage monitor, it can be realized by using these. Incidentally, 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 abruptly.
Then, when the EGR valve is closed and the recirculation amount of the exhaust gas decreases, the amount of inert gas in the air-fuel mixture decreases and the combustion energy of the air-fuel mixture increases. When the EGR valve is opened and the recirculation amount of 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, during the failure diagnosis of the EGR system, the combustion energy of the air-fuel mixture is suddenly changed due to the forced closing and opening of the EGR valve. This causes fluctuations in the torque generated by the internal combustion engine, which may cause deterioration of drivability such as fluctuations in the rotational speed. 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 according to the compulsory closing and opening timings of the EGR valve or the fluctuation range of the rotational speed. This suppresses rotation fluctuations and prevents deterioration of drivability. Hereinafter, a method of correcting this torque fluctuation will be described with reference to the flowchart of FIG. FIG. 8 is a flow chart executed at a constant time or for each angle. In this flowchart, step 101 is the pre-correction ignition timing θ _IGO calculated by the ignition timing control routine. Step 10
In Step 2, diagnose whether the EGR system failure diagnosis is in progress,
If it is under diagnosis, go 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 open or closed. When the valve is open, the rotation fluctuation dN /
Calculate dt. In step 112, the advance angle amount Δθ _AD is calculated, and in step 113, the value obtained by subtracting Δθ _AD from θ _{IGO is} set as the ignition timing θ _IG . When the valve is closed, the rotation fluctuation dN / dt is calculated in step 104. In step 105, the retard angle amount Δθ _LE is calculated, and in step 106, the 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 the failure diagnosis of the EGR system, it is possible to suppress the rotation fluctuation due to the abrupt change of the exhaust gas recirculation amount, and thus it is possible to prevent the deterioration of the drivability. In addition, from the physical quantity by the ventilation of the correction ventilation system including the EGR system that is sucked into the intake pipe,
If the EGR system failure diagnosis is performed after the physical quantity 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. The present invention will be described below with reference to FIG. 9 in which the canister purge system is also used. In step 31, the operating state of the internal combustion engine is detected by the signal from the sensor group, and then 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 to a predetermined opening. In step 36, the EGR valve 5 is closed and the EGR passage 4 is shut off. When the predetermined time T ₁ has elapsed in step 37, the intake pipe pressure Pb is measured in step 38 and set as Pb ₀ . Then in step 39, E
The GR valve 5 is opened and the EGR passage 4 is opened. Step 4
When a predetermined time T _{2 of} 0 has elapsed, step 4
In step 1, the intake pipe pressure Pb is measured and designated as Pb ₁ . Next, at step 42, the difference between Pb ₁ and Pb ₀ is set to ΔPb. In step 141, the negative pressure Pc generated by the canister purge
To calculate. As a means for calculating this Pc, for example, the characteristic of the change of Pc due to the change of 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 from time to time, and a method of calculating the value of Pc 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 represented by Equation 1, and Equation 2 is represented by Equation 2.

[Equation 1]

[Equation 2] However, α: flow coefficient A: cross-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 '. In step 143, the predetermined value PT determined from the operating condition is compared with ΔPb ′, and if ΔPb ′ is larger than PT, it is determined in step 44 that the EGR system is normal.
If ΔPb 'is less than or equal to PT, EG is performed in steps 51 and 52.
It is determined that the R system is out of order. The present invention is
The diagnosis target can be applied to a correction ventilation system other than the EGR system. According to the above means, even if a structurally special device such as an electromagnetic valve is not prepared in the ventilation system or the like, the failure diagnosis area can be widened, and the accuracy of the EGR system failure diagnosis can be improved. The above is the description of the self-diagnosis device for the EGR system. However, if at least one correction ventilation system including the EGR system connected to the intake pipe is provided with a means for forcibly blocking the ventilation, It is possible to carry out a failure diagnosis of the correction ventilation system. An embodiment of the present invention will be described below with reference to the flowchart of FIG. In this embodiment, a case of performing a failure diagnosis of the canister purge system of the correction ventilation system will be described. In step 71 of FIG. 10, the operating state of the internal combustion engine is detected by a signal from the sensor group similarly to step 31 of FIG. 3, and then in step 72, the operating state is predetermined. Or not. If it is in the diagnostic area, the process proceeds to step 73. If it is not in the diagnostic region, the diagnosis is stopped. At steps 73, 74, and 75, the control valves of the EGR system, the blow-by gas recirculation system, and the ISC system, which are the correction ventilation systems other than the diagnosis target, are closed to shut off the ventilation path. Next, at step 76, the canister purge valve is closed to shut off the passage of the canister purge system to be diagnosed. Time T predetermined in step 77
_{When 3} has elapsed, the intake pipe pressure Pb is measured at step 78 and is referred to as Pb ₂ . Next, at step 79, the canister purge valve is opened and the passage is opened. 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 ΔPb, and in step 83 it is compared with a predetermined value PT ₁ determined from the operating condition. Δ in step 83
If Pb is larger than PT ₁ , it is determined in step 84 that the canister purge engine is normal. If ΔPb is PT ₁ or less in step 83, it is determined in step 91 that the ventilation system of the canister purge system has failed. If it is determined that there is a failure, the display device is turned on in step 92 to notify the driver of the failure. If the diagnostic information is stored in a memory having a backup power source 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 the same procedure. Needless to say, the method of the EGR system shown in FIGS. 3, 5, 8 and 9 can also be used in these correction ventilation systems. Lastly, the present invention has been described with reference to the embodiment in which the diagnosis of the control valve is performed, but it is possible to diagnose from the operation of the control valve in each passage as well. 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, it is possible to accurately diagnose the correction ventilation system without impairing the braking effect of the engine brake.

[Brief description of 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 opening and closing an EGR valve.

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

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

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

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.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location F02M 25/08 301 U 7114-3G (72) Inventor Toshio Ishii 2520 Takaba, Takata, Ibaraki Prefecture Hitachi, Ltd. Automotive Equipment Division

Claims (13)

[Claims] 1. A main ventilation system that sends a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to an internal combustion engine; and a combustible material for the internal combustion engine that is separate from the main ventilation system. And / or at least two or more correction ventilation systems for sending a non-combustible gas, and a diagnosis means for diagnosing at least one correction ventilation system of the correction ventilation system. Is operable to execute the diagnosis when the fuel is supplied from the fuel supply device and the correction ventilation system other than the correction ventilation system to be diagnosed is substantially inactive. Device for a corrected ventilation system used in a running internal combustion engine. 2. A main ventilation system for sending to the internal combustion engine a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device, and a combustible material for the internal combustion engine, separate from the main ventilation system. And / or at least two or more correction ventilation systems for sending a non-combustible gas, and a diagnosis means for diagnosing at least one correction ventilation system of the correction ventilation system. Is operated so as to execute the diagnosis when the fuel is being supplied from the fuel supply device and the correction ventilation system other than the correction ventilation system to be diagnosed is in an operating state in which the correction ventilation system does not substantially operate. Device for a corrected ventilation system used in a running internal combustion engine. 3. A main ventilation system for sending to the internal combustion engine a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device, and a combustible material for the internal combustion engine, which is separate from the main ventilation system. And / or at least two or more correction ventilation systems for sending a non-combustible gas, and a diagnosis means for diagnosing at least one correction ventilation system of the correction ventilation system. Operates in such a manner that the correction ventilation system other than the correction ventilation system to be diagnosed is forcibly deactivated while the fuel is being supplied from the fuel supply device. A diagnostic device for a corrected ventilation system used in an internal combustion engine. 4. A main ventilation system for sending to the internal combustion engine a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device; and a combustible material for the internal combustion engine, which is separate from the main ventilation system. And / or at least two or more compensating ventilation systems for sending a non-flammable gas, a control valve provided in the compensating ventilation system, and a diagnosis of operation of at least one control valve of the control valves. In the diagnosis means, the control valve of the correction ventilation system other than the correction ventilation system to be diagnosed is substantially inoperative while the fuel is being supplied from the fuel supply device. A diagnostic device for a corrected ventilation system used in an internal combustion engine, characterized in that it operates so as to perform diagnostics when in a state. 5. A main ventilation system for sending to the internal combustion engine a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device, and a combustible material for the internal combustion engine separately from the main ventilation system. And / or at least two or more compensating ventilation systems for sending a non-flammable gas, a control valve provided in the compensating ventilation system, and a diagnosis of operation of at least one control valve of the control valves. An operation in which the control valve of the correction ventilation system other than the correction ventilation system to be diagnosed is not substantially operated in a state in which fuel is being supplied from the fuel supply device. A diagnostic device for a corrected ventilation system used in an internal combustion engine, characterized in that it operates so as to perform diagnostics when in a state. 6. A main ventilation system for sending to the internal combustion engine a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device, and a combustible material for the internal combustion engine separately from the main ventilation system. And / or at least two or more compensating ventilation systems for sending a non-flammable gas, a control valve provided in the compensating ventilation system, and a diagnosis of operation of at least one control valve of the control valves. And a diagnostic means, wherein the diagnostic means forcibly deactivates the control valve of the correction ventilation system other than the correction ventilation system to be diagnosed while the fuel is being supplied from the fuel supply device. A diagnostic device for a correction ventilation system used in an internal combustion engine, which is operated so as to perform a diagnostic when brought into a state. 7. The correction ventilation used in an internal combustion engine according to claim 1, wherein one of the correction ventilation systems is an EGR system for returning exhaust gas from an exhaust passage of the internal combustion engine to the main ventilation system. System diagnostic device. 8. The EGR system according to claim 1, wherein the correction ventilation system recirculates exhaust gas from an exhaust passage of the internal combustion engine to the main ventilation system,
A diagnostic device for a correction ventilation system used in an internal combustion engine, which is a canister purge system that adsorbs fuel vapor generated in a fuel tank to a canister and supplies it again to the main ventilation system. 9. The diagnosis means according to claim 1, wherein the diagnostic means detects a change in a physical quantity caused by the internal combustion engine when the correction ventilation system to be diagnosed is operated and when it is not operated and diagnosed. An apparatus for diagnosing a corrected ventilation system used in an internal combustion engine for diagnosing a corrected ventilation system. 10. A correction used for an internal combustion engine in which a torque fluctuation suppressing means for suppressing a torque fluctuation of the internal combustion engine due to the diagnosis is operated when the diagnosis by the diagnostic means is executed. Ventilation system diagnostic device. 11. A diagnosis of a correction ventilation system used in an internal combustion engine as an ignition timing correction means for detecting a rotation fluctuation and controlling an ignition timing so as to suppress the rotation fluctuation, according to claim 10. apparatus. 12. A main ventilation system that sends a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to an internal combustion engine, and exhaust gas of the internal combustion engine is returned to the main ventilation system. An EGR system including an exhaust gas recirculation passage and an exhaust gas control valve arranged in the exhaust gas recirculation passage, a canister that adsorbs fuel vapor in a fuel tank that stores fuel in the fuel supply device, and a fuel vapor in the canister. A canister purge system comprising a purge passage for supplying to the main ventilation system and a purge control valve arranged in the purge passage, and a diagnostic means for diagnosing the EGR system, wherein the diagnostic means comprises: The fuel is supplied from the supply device, and the canister purge system is substantially inoperative. In this state, the EGR system is abnormal 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 less than or equal to a predetermined value. A diagnostic device for a corrected ventilation system used in an internal combustion engine, which is characterized by executing a diagnosis for determining that 13. A main ventilation system that sends a mixture of air supplied through an air cleaner and fuel supplied through a fuel supply device to an internal combustion engine, and a combustible material for the internal combustion engine that is separate from the main ventilation system. And / or at least two or more correction ventilation systems for sending a non-combustible gas, and a diagnosis means for diagnosing at least one correction ventilation system of the correction ventilation system. Is a physical quantity obtained by subtracting a physical quantity generated by the operation of the correction ventilation system that is not a diagnosis target from the physical quantity of the internal combustion engine when the correction ventilation system is operating in the state where the fuel is supplied from the fuel supply device. A diagnostic device for a corrected ventilation system used in an internal combustion engine for diagnosing a corrected ventilation system to be diagnosed.