JP2016151210A - Egr cooler diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR cooler diagnostic system that can detect an abnormality of an EGR cooler by using a sensor normally provided in a commonly used engine.SOLUTION: An EGR cooler diagnostic system detects an abnormality of an EGR cooler 53 provided in an EGR device 50 of an engine 1. The engine includes: knock detection means 12 for detecting knock; and throttle control means for controlling an opening of a throttle valve 24 so that actual torque corresponds to required torque. The EGR cooler diagnostic system includes abnormality determination means 100 that determines abnormality when the frequency of knock is equal to or larger than a knock frequency determination value set based on the knock frequency in a normal state of the EGR cooler and the throttle valve opening is equal to or larger than a throttle opening determination value set based on the throttle valve opening in the normal state of the EGR cooler while the engine is in a predetermine steady operation state.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a diagnostic device for an EGR cooler that cools EGR gas in an EGR device that extracts a part of exhaust gas from an engine and introduces it into an intake pipe as EGR gas, and in particular, a sensor that is usually provided in a general engine. It is related with what can detect abnormality of EGR cooler.

For example, in a 4-stroke gasoline engine mounted in an automobile or the like, an EGR device that extracts a part of exhaust gas (burned gas) from a combustion chamber from an exhaust port or an exhaust pipe and introduces (recirculates) the exhaust gas into an intake pipe Is provided.
Since the exhaust gas is substantially an inert gas, by introducing it into the combustion chamber via the intake pipe, it is possible to reduce the combustion temperature and suppress the generation of NOx.
Further, by performing EGR at the time of partial load, the throttle valve opening for obtaining the same torque is increased, so that fuel efficiency can be improved by reducing pump loss.

When a failure occurs in the EGR device, there is a concern that various performances such as fuel efficiency and exhaust gas may be adversely affected. Therefore, it is desired to perform on-board diagnosis of the EGR device using sensors mounted on the vehicle while the vehicle is in use. ing.
As a conventional technique related to on-board diagnosis of an EGR device, for example, Patent Document 1 discloses that a difference between an intake pressure estimated from an airflow meter output and a detected value of an actual intake pressure is equal to or greater than a threshold value and a throttle in a transient state. It is described that the abnormality of the EGR device is determined when the deviation between the change amount of the intake pressure estimated from the opening degree of the valve and the actual change amount of the intake pressure is equal to or greater than a threshold value.
Further, Patent Document 2 describes that in an operation region where exhaust gas recirculation (EGR) is performed, it is determined that the exhaust gas recirculation device has failed when occurrence of knocking is detected a predetermined number of times or more. Has been.
Patent Document 3 describes that a failure of the EGR device is determined based on a change in the actual opening of the electric throttle valve when the EGR valve is operated.

In recent years, EGR coolers that cool EGR gas by heat exchange with engine cooling water, etc., and reduce the intake air temperature to improve the knocking prevention effect and the like are becoming widespread.
Although the EGR valve sticking or EGR pipe blockage can be diagnosed by the above-described conventional diagnostic method, even if there is no such problem, the EGR cooler may be damaged or malfunctioned. If it occurs and the EGR gas cannot be cooled normally, there is a concern that the temperature of the EGR gas is improved and the engine performance is adversely affected.
On the other hand, Patent Document 4 describes that the boiling of the cooling water of the EGR cooler is detected according to the energization resistance value of the SiC-EGR cooler that can be energized.

JP 2011-169200 A JP-A-63-239351 JP 2001-182602 A JP 2013-185519 A

In the technique described in the cited document 4 described above, the applicable EGR cooler is limited to the SiC-EGR cooler, and a power source for applying a voltage thereto, a sensor for measuring an energization resistance value, and the like are necessary. The structure becomes complicated.
Also, for example, an EGR cooler abnormality can be detected by providing a sensor for detecting the temperature of the EGR gas downstream of the EGR cooler. In this case, however, a dedicated temperature sensor may be newly added. It becomes necessary to make the structure complicated and increase the number of parts.
In view of the above-described problems, an object of the present invention is to provide an EGR cooler diagnostic apparatus that can detect an abnormality of an EGR cooler using a sensor that is usually provided in a general engine.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is an EGR cooler diagnostic device that detects an abnormality of an EGR cooler that is provided in an EGR device that extracts a part of exhaust gas of an engine as EGR gas and introduces it into an intake pipe, and cools the EGR gas. The engine includes knock detection means for detecting knock, and throttle control means for controlling the throttle valve opening so that the actual torque matches the required torque, and the EGR cooler diagnostic device includes the engine Is the knock frequency determination value set based on the knock frequency in the normal state of the EGR cooler, and the throttle valve opening is normal of the EGR cooler. When the throttle opening degree is greater than the throttle opening degree judgment value set based on the throttle valve opening degree A EGR cooler diagnostic apparatus characterized by comprising abnormality determination means for standing.
According to this, when the EGR cooler breaks down or breaks and the EGR gas becomes higher than normal, knocking is likely to occur due to an increase in the intake air temperature, and the charging efficiency is reduced. Based on the output of the knock detection means (knock sensor) normally provided in the case of a general engine and the opening of the electric throttle valve, using the fact that the throttle opening is set large if the target torque is the same, Abnormality of the EGR cooler can be appropriately detected without adding new sensors.
Here, the predetermined steady operation state is, for example, that the engine speed, the intake air amount, and the valve opening of the EGR device are within preset ranges, and the fluctuation amount thereof is sufficiently small. It is done.

The invention according to claim 2 is a determination value correction that corrects at least one of the knock frequency determination value and the throttle opening determination value according to at least one of an operating state of the engine and an environmental state in which the engine is operated. The EGR cooler diagnostic apparatus according to claim 1, further comprising: means.
According to this, the diagnostic accuracy can be further improved by appropriately correcting the knock frequency determination value and the throttle opening determination value according to the engine operating state and the environmental state.
For example, knocking is likely to occur when the outside air temperature is high, and the throttle opening needs to be increased in order to obtain the same torque as the charging efficiency deteriorates. It is preferable to increase both the knock frequency determination value and the throttle opening determination value.
Also, when the atmospheric pressure is low (oxygen is thin) at high altitudes, knocking is likely to occur and the charging efficiency is also deteriorated. Therefore, the knock frequency determination value and the throttle opening degree determination according to the decrease in atmospheric pressure. It is better to increase both values.
In the case of an engine in which the knock frequency and the throttle opening change when the ignition timing is retarded (retarded) while the EGR cooler is in a normal state, the knock frequency judgment value and the throttle opening are changed according to the ignition timing retard amount. The degree determination value may be corrected as appropriate.

  As described above, according to the present invention, it is possible to provide an EGR cooler diagnostic apparatus that can detect an abnormality of an EGR cooler using a sensor that is normally provided in a general engine.

It is a schematic diagram which shows the structure of the engine containing the Example of the EGR cooler diagnostic apparatus to which this invention is applied. It is a flowchart which shows operation | movement of the EGR cooler diagnostic apparatus of an Example.

  The present invention provides a problem of providing an EGR cooler diagnostic device that can detect an abnormality of an EGR cooler using a sensor that is usually provided in a general engine. The engine rotation speed, intake air amount, and EGR valve opening degree are all included. EGR when the engine knock sensitivity (knock frequency) and the throttle valve opening are both equal to or greater than a judgment value set based on the value when the EGR cooler is normal within a predetermined diagnosable range and in a steady state. The problem was solved by establishing a cooler abnormality determination.

Embodiments of an EGR cooler diagnostic apparatus to which the present invention is applied will be described below.
The EGR cooler diagnostic apparatus according to the embodiment includes, for example, an abnormality of an EGR cooler included in an EGR apparatus provided in an engine mounted as a traveling power source alone or in combination with an electric drive device such as a motor generator in an automobile such as a passenger car. Is to discriminate.
FIG. 1 is a schematic diagram illustrating a configuration of an engine including an EGR cooler diagnostic apparatus according to an embodiment.
The engine 1 includes a main engine 10, an intake device 20, an exhaust device 30, a fuel supply device 40, an EGR device 50, an engine control unit 100, and the like.

The main machine 10 is a main body part of the engine 1.
In the embodiment, the engine 1 is, for example, a horizontally opposed four-cylinder four-stroke gasoline engine, and is installed vertically in an engine room provided at the front of the vehicle.
The main machine 10 includes a crankshaft 11, a crankcase 12, a cylinder 13, a cylinder head 14, and the like.
The crankshaft 11 is an output shaft of the engine 1 and includes a piston pin connected to a piston (not shown) via a connecting rod (not shown), a journal portion supported by the crankcase 12, and the like. .

The crankshaft 11 is provided with a crank angle sensor 11a that detects its angular position.
The crank angle sensor 11 a outputs a pulse signal corresponding to the rotation of a sprocket-like sensor plate fixed to the end of the crankshaft 11.
The output of the crank angle sensor 11a is transmitted to the engine control unit 100.

The crankcase 12 is a container-like part that accommodates the crankshaft 11 and is formed in a left-right split with the crankshaft 11 in between. Meaning left and right directions).
The crankcase 12 is formed with a bearing portion that rotatably supports a journal portion (shaft portion) of the crankshaft 11.
The left and right members of the crankcase 12 are formed integrally with the cylinders 13 of the left and right banks.
The crankcase 12 is provided with a knock sensor 12a.
The knock sensor 12a detects vibration of the crankcase 12 in a knock generation region (for example, 5 to 15 kHz region) by a vibration pickup having piezoelectric ceramics.
The output signal of knock sensor 12a is transmitted to engine control unit 100.
The engine control unit 100 detects knock by converting the detected signal into the angular velocity of the crankshaft 11.

The cylinder 13 has a cylinder bore into which a piston (not shown) is inserted, a water jacket through which cooling water flows, and the like.
The cylinder 13 is provided with left and right banks on both sides of the crankcase 12.

The cylinder heads 14 are respectively provided at the ends of the left and right banks of the cylinders 13 opposite to the crankcase 12 side.
The cylinder head 14 is provided with a combustion chamber, an intake / exhaust port, an intake / exhaust valve, a valve drive system, a water jacket, and the like.
The cylinder head 14 is provided with a spark plug 14a that ignites the air-fuel mixture in the combustion chamber.
The spark plug 14a generates a spark in response to an ignition signal transmitted from the engine control unit 100.

The intake device 20 introduces combustion air (fresh air) into the intake port of the main engine 10.
The intake device 20 includes an intake duct 21, an air cleaner 22, an air flow meter 23, a throttle valve 24, an intake manifold 25, and the like.

The intake duct 21 is a conduit that sucks outside air from an inlet provided at the front of the vehicle and introduces it into the inlet of the throttle valve 24.
The air cleaner 22 removes foreign matters such as dust and sand from the air (fresh air) flowing through the intake duct 21 by filtering with a filter element.
The air cleaner 22 is provided in the vicinity of the inlet portion of the intake duct 21.
The air flow meter 23 is provided adjacent to the outlet side of the air cleaner 22 and measures the flow rate of fresh air (intake air amount of the engine 1) passing through the intake duct 21.
The output of the air flow meter 23 is transmitted to the engine control unit 100.

The throttle valve 24 has a butterfly valve driven by, for example, an electric actuator, and is a throttle valve that adjusts the intake air amount for adjusting the output of the engine 1.
The engine control unit 100 sets the target generated torque of the engine 1 based on the driver request torque set based on the accelerator pedal opening, etc., so that the actually generated torque (actual torque) approaches the target generated torque. In addition, the opening degree of the throttle valve 24 is feedback-controlled.

The intake manifold 25 is a branch pipe that distributes and introduces fresh air that has passed through the throttle valve 24 to the intake ports of the cylinders of the left and right banks.
EGR gas obtained by extracting a part of the exhaust gas from the engine 1 is introduced into the intake manifold 25 by an EGR device 50 described later.

The exhaust device 30 discharges exhaust gas (burned gas) of the engine 1.
The exhaust device 30 includes an exhaust manifold 31, a catalytic converter 32, and the like.
The exhaust manifold 31 is a collecting pipe that collects exhaust gas discharged from the exhaust ports of the cylinders of the left and right banks and introduces the exhaust gas into the catalytic converter 32.
The catalytic converter 32 includes a three-way catalyst configured by supporting a noble metal such as platinum, rhodium, and palladium on a carrier formed of, for example, alumina.
The catalytic converter 32 is a post-processing device that processes HC, NOx, and CO in the exhaust gas introduced from the exhaust manifold 31.
The treated exhaust gas exiting the catalytic converter 32 is discharged outside the vehicle through an exhaust pipe (not shown) having a silencer or the like.

The fuel supply device 40 sprays fuel (gasoline) into fresh air introduced into the combustion chamber of each cylinder to form a combustion air-fuel mixture.
The fuel supply device 40 includes an injector 41, a delivery pipe 42, and the like.

The injector 41 is provided near the end of the intake manifold 25 on the intake port side.
The injector 41 sprays pressurized fuel introduced from the delivery pipe 42 into the intake port over a predetermined valve opening timing.
The injector 41 opens in response to a valve opening signal transmitted from the engine control unit 100.

The delivery pipe 42 is a pipeline that conveys fuel pressurized by a fuel pump from a fuel tank (not shown) to the injector 41.
The fuel in the delivery pipe 42 is adjusted to a predetermined pressure by a regulator (not shown).
Excess fuel not injected by the injector 41 is returned to the fuel tank via a return pipe (not shown).

The EGR device 50 extracts a part of the exhaust gas (burned gas) of the engine 1 and introduces (returns) it into the intake manifold 25.
The EGR device 50 includes an EGR pipe line 51, an EGR valve 52, an EGR cooler 53, and the like.

  The EGR pipe line 51 is a pipe line that extracts a part of the exhaust gas from the exhaust port of the cylinder head 14 as EGR gas and returns it to the intake manifold 25.

The EGR valve 52 is provided in the middle of the EGR pipe 51 and adjusts the flow rate of EGR gas passing through the EGR pipe 51.
The EGR valve 52 can change the flow rate stepwise from fully closed to fully opened by a stepping motor that opens and closes the valve body.
The step value of the stepping motor is instructed by the engine control unit 100.
The stepping motor increases the opening degree of the EGR valve 52 stepwise in accordance with an increase in the step value that is instructed.

The EGR cooler 53 cools the EGR gas flowing through the EGR pipe 51 by heat exchange with the cooling water of the engine 1.
The EGR cooler 53 is provided on the downstream side of the EGR valve 52 (intake manifold 25 side) in the EGR pipe line 51.

The engine control unit (ECU) 100 is a control device that comprehensively controls the engine 1 and its accessories.
The engine control unit 100 includes information processing means such as a CPU, storage means such as RAM and ROM, an input / output interface, a bus connecting these, and the like.

An accelerator opening sensor 101, an outside air temperature sensor 102, an atmospheric pressure sensor 103, and the like are connected to the engine control unit 100.
The accelerator opening sensor 101 is an encoder that detects an operation amount (depression stroke) of an accelerator pedal for a driver to perform an accelerator operation.
The engine control unit 100 calculates the driver request torque based on the output of the accelerator opening sensor 101.
The outside air temperature sensor 102 detects outside air temperature around the vehicle.
The atmospheric pressure sensor 103 detects the atmospheric pressure around the vehicle.
The outputs of these sensors are transmitted to the engine control unit 100, respectively.

The engine control unit 100 has a function of detecting an abnormality such as a failure or breakage of the EGR cooler 53.
As a form of failure or breakage of the EGR cooler 53, for example, there is a state in which the EGR gas cannot be normally cooled due to a hole or crack in one of the flow paths of EGR gas or cooling water.
The engine control unit 100 functions as an abnormality determination means in the embodiment of the EGR cooler diagnostic apparatus according to the present invention.

The engine control unit 100 also has a function of diagnosing whether the EGR valve 52 of the EGR device 50 is stuck or the EGR pipe 51 is blocked or broken.
Such a diagnosis is performed using various known diagnostic techniques, for example, by monitoring pressure fluctuations in the intake manifold 25 when the EGR valve 52 is suddenly opened and closed when the fuel of the engine 1 is cut. It is possible.
The diagnosis of the EGR cooler described below is performed on the assumption that the EGR pipe 51, the EGR valve 52, and the like are normal.

FIG. 2 is a flowchart illustrating the operation of the EGR cooler diagnostic apparatus according to the embodiment.
Hereinafter, the steps will be described step by step.
<Step S01: Acquisition of rotational speed, intake air amount, EGR step>
The engine control unit 100 acquires information on the rotation speed (rotation speed) of the crankshaft 11 of the engine 1, the intake air amount, and the EGR step.
The rotation speed is detected based on the output of the crank angle sensor 11a.
The intake air amount is detected based on the output of the air flow meter 23.
The EGR step is a step value currently instructed to the stepping motor of the EGR valve 52.
Thereafter, the process proceeds to step S02.

<Step S02: Satisfaction determination of diagnosis execution condition>
The engine control unit 100 determines whether or not a diagnosis execution condition for preset EGR cooler diagnosis is satisfied.
The diagnosis execution condition is, for example, that the rotation speed (rotation speed) of the crankshaft 11 of the engine 1, the intake air amount, and the step value (EGR step) of the EGR valve 52 are each within a preset diagnosis execution range and predetermined. This is a steady state without the above fluctuations.
If the diagnosis execution condition is satisfied, the process proceeds to step S03. If not satisfied, the process returns to step S01, and the subsequent processing is repeated.

<Step S03: Knock Sensitivity Calculation>
The engine control unit 100 calculates the knock sensitivity within the latest predetermined period (for example, the latest 5 seconds) based on the output of the knock sensor 12a.
The knock sensitivity is a parameter indicating the frequency of occurrence of knocks in a plurality of cycles in the engine 1.
The knock sensitivity is calculated, for example, by integrating a value obtained by converting vibration detected by the knock sensor 12a into an angular velocity of the crankshaft 11 over a predetermined number of cycles.
The knock sensitivity, which is such an integrated value, has a characteristic that increases as the occurrence frequency (deterioration) of knock occurs.
Thereafter, the process proceeds to step S04.

<Step S04: Knock Sensitivity Determination Value Correction Value Calculation>
The engine control unit 100 sets the knock sensitivity determination value based on the knock sensitivity acquired in advance when the EGR cooler 53 is normal in the current engine speed, intake air amount, and EGR step.
The knock sensitivity determination value is set by adding a predetermined value (error tolerance) to the normal knock sensitivity in order to prevent erroneous detection.
Thereafter, the engine control unit 100 corrects the knock sensitivity determination value according to the operating state of the engine 1 and the environmental conditions around the vehicle, and calculates the knock sensitivity determination value correction value.
For example, the knock sensitivity determination value is corrected so as to increase as the outside air temperature increases, reflecting that the intake air temperature increases as the outside air temperature increases and knocking is likely to occur.
Further, the knock sensitivity determination value is corrected so as to increase as the atmospheric pressure decreases because knocking is likely to occur even when the atmospheric pressure decreases.
Further, when the knock sensitivity changes due to the ignition timing delay (retard), the knock sensitivity determination value is appropriately corrected according to the retard amount of the ignition timing.
After calculating the knock sensitivity determination value correction value subjected to various corrections, the process proceeds to step S05.

<Step S05: Knock Sensitivity Determination>
The engine control unit 100 compares the actual knock sensitivity detected in step S03 with the knock sensitivity determination value correction value calculated in step S04.
If the knock sensitivity is greater than or equal to the knock sensitivity determination value correction value, the process proceeds to step S06, and otherwise the process proceeds to step S10.

<Step S06: Obtain throttle opening>
The engine control unit 100 acquires information related to the average value of the throttle opening that has been instructed to the actuator of the throttle valve 24 during the latest predetermined period (for example, the latest 5 seconds).
Thereafter, the process proceeds to step S07.

<Step S07: Calculation of Correction Value for Throttle Opening Determination Value>
The engine control unit 100 sets a throttle opening degree determination value based on the throttle opening degree acquired in advance when the EGR cooler 53 is in a normal state at the current engine speed, intake air amount, and EGR step.
The throttle opening determination value is set by adding a predetermined value (error tolerance) to the normal throttle opening in order to prevent erroneous detection.
Thereafter, the engine control unit 100 corrects the throttle opening degree determination value according to the operating state of the engine 1 and the environmental conditions around the vehicle, and calculates the throttle opening degree determination value correction value.
For example, when the outside air temperature increases, the intake air temperature increases, and the throttle opening degree needs to be opened to generate the same torque as the outside air temperature increases. It is corrected to increase accordingly.
Further, the throttle opening determination value is corrected so as to increase as the atmospheric pressure decreases because the charging efficiency deteriorates even when the atmospheric pressure decreases.
Further, when the throttle opening changes due to the ignition timing delay, the throttle opening determination value is appropriately corrected according to the retard amount of the ignition timing.
After calculating the throttle opening determination value correction value subjected to various corrections, the process proceeds to step S08.

<Step S08: Determination of throttle opening>
The engine control unit 100 compares the current throttle opening acquired in step S06 with the throttle opening determination value correction value calculated in step S07.
If the throttle opening is equal to or greater than the throttle opening determination value correction value, the process proceeds to step S09, and otherwise the process proceeds to step S10.

<Step S09: Establishment of abnormality determination>
The engine control unit 100 establishes the abnormality determination of the EGR cooler 53.
The engine control unit 100 outputs a predetermined alarm or the like to notify a driver or the like that an abnormality has occurred and changes the control mode of the engine 1 from the mode used during normal operation to when the EGR cooler 53 is malfunctioning. Then, the mode is switched to the preset fail-safe mode, and the series of processes is terminated.

<Step S10: Establishment of normality determination>
The engine control unit 100 establishes the normality determination of the EGR cooler 53.
Thereafter, the series of processing is terminated.

As described above, according to the embodiment, the following effects can be obtained.
(1) When the operating state of the engine 1 satisfies predetermined diagnosis execution conditions (rotation speed, intake air amount, EGR step value), each of the EGR coolers 53 takes into account knock sensitivity and throttle opening when normal A general engine is established by establishing an abnormality determination when both the actual knock sensitivity and throttle opening exceed the set knock sensitivity determination value (correction value) and throttle opening determination value (correction value). The abnormality of the EGR cooler 53 can be detected using only the sensors normally provided in the system.
(2) The diagnostic accuracy can be further improved by correcting each determination value according to the outside air temperature, the atmospheric pressure, the ignition timing retard amount, and the like.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
For example, if the engine to be diagnosed is a four-stroke engine having spark ignition and an electric throttle valve, cylinder layout, number of cylinders, presence / absence and type of supercharger, fuel injection location (port / cylinder), etc. There is no particular limitation.
Also, a knock detection method, a knock frequency calculation method, a correction method for each determination value, and the like are not particularly limited.
For example, in the embodiment, the knock sensitivity (knock frequency) is calculated using the integrated value of the value obtained by converting the vibration detected by the knock sensor into the angular velocity of the crankshaft. You may calculate using the angular velocity of the crankshaft to detect.
Further, a counter value obtained by counting the number of occurrences of knocking within the latest predetermined period may be used as the knocking frequency.
In addition, the knock frequency and the throttle opening when the EGR cooler is normal only need to acquire one value for each of the engine rotation speed, the intake air amount, and the EGR valve opening at a specific minimum level. When it is desired to improve the execution frequency of the cooler diagnosis, the knock frequency and the throttle opening corresponding to the variation of each parameter may be acquired in advance and held in a map state, for example.

DESCRIPTION OF SYMBOLS 1 Engine 10 Main machine 11 Crankshaft 11a Crank angle sensor 12 Crankcase 12a Knock sensor 13 Cylinder 14 Cylinder head 14a Spark plug 20 Intake device 21 Intake duct 22 Air cleaner 23 Air flow meter 24 Throttle valve 25 Intake manifold 30 Exhaust device 31 Exhaust manifold 32 Catalyst Converter 40 Fuel supply device 41 Injector 42 Delivery pipe 50 EGR device 51 EGR conduit 52 EGR valve 53 EGR cooler 100 Engine control unit 101 Accelerator opening sensor 102 Ambient air temperature sensor 103 Atmospheric pressure sensor

Claims (2)

An EGR cooler diagnosis device that detects an abnormality of an EGR cooler that is provided in an EGR device that extracts a part of engine exhaust gas as EGR gas and introduces it into an intake pipe, and cools the EGR gas,
The engine has knock detection means for detecting knock, and throttle control means for controlling the throttle valve opening so that the actual torque matches the required torque,
When the engine is in a predetermined steady operation state, the EGR cooler diagnostic device has a knock frequency equal to or higher than a knock frequency determination value set based on a knock frequency in a normal state of the EGR cooler, and the throttle An EGR cooler diagnosis apparatus comprising: an abnormality determination unit that establishes an abnormality determination when the valve opening is equal to or greater than a throttle opening determination value set based on a throttle valve opening in a normal state of the EGR cooler. . And a determination value correcting unit that corrects at least one of the knock frequency determination value and the throttle opening determination value according to at least one of an operating state of the engine and an environmental state in which the engine is operated. The EGR cooler diagnostic apparatus according to claim 1.

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