JP2015124725A - Failure diagnosis device for egr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnosis device for an EGR device capable of completing failure diagnosis of an EGR device at an earlier stage compared to a conventional one, and capable of suppressing generation of engine stall when restarting an internal combustion engine during the failure diagnosis of the EGR device.SOLUTION: A failure diagnosis device for an EGR device including an EGR valve opening adjusting unit includes: an intake pressure sensor for detecting an intake pressure; and a failure diagnosis unit for performing failure diagnosis of the EGR device on condition that an EGR diagnosis condition is established. The EGR valve opening adjusting unit, after the establishment of the EGR diagnosis condition, makes a maximum opening of the EGR valve a fine opening until duration time T1 elapses, and makes the maximum opening of the EGR valve a target opening after the elapse of the duration time T1. The failure diagnosis unit performs failure diagnosis based on an intake pressure Pin1 until the duration time T1 elapses and an intake pressure Pin2 after the elapse of the duration time T1.

Description

  The present invention relates to a failure diagnosis device for an EGR device, and more particularly to a failure diagnosis device for an EGR device that recirculates a part of exhaust gas discharged from an internal combustion engine mounted on a vehicle to an intake passage.

  Conventionally, for the purpose of reducing NOx in the exhaust gas, an EGR passage that connects the exhaust passage and the intake passage is provided, and a part of the exhaust gas discharged from the internal combustion engine through the EGR passage is used as the intake passage. There is known an EGR device that is recirculated and sucked into an internal combustion engine again. Generally, in such an EGR device, an EGR valve for adjusting the amount of exhaust gas recirculated to the intake passage is provided on the EGR passage.

  In such an EGR device, the EGR valve may fail due to, for example, aging, or the EGR passage may be clogged due to accumulation of unburned hydrocarbons or the like. Normally, such a failure or clogging cannot be grasped by the driver, and is detected by a failure diagnosis device mounted on the vehicle.

  As a failure diagnosis device for this type of EGR device, for example, a failure diagnosis device as described in Patent Document 1 is known. The failure diagnosis apparatus described in Patent Document 1 is an intake air amount when the EGR valve is fully opened and a part of the exhaust gas is recirculated to the intake passage, and an intake air amount when the EGR valve is fully closed. Is determined to be within a predetermined threshold, thereby performing failure diagnosis for detecting whether the EGR device has a failure or clogging.

  Further, in the failure diagnosis apparatus described in Patent Document 1, the failure diagnosis of the EGR device as described above is performed after a predetermined delay time has elapsed after a predetermined diagnosis condition such as the vehicle being decelerated is satisfied. . Thereby, the failure diagnosis apparatus can scavenge the exhaust gas remaining in the exhaust passage before performing the failure diagnosis with the EGR valve fully opened. Therefore, according to the failure diagnosis apparatus, it is possible to prevent, for example, exhaust gas containing unburned fuel components from flowing into the EGR cooler provided in the EGR passage when the failure diagnosis is performed. It is possible to prevent clogging of the inside of the EGR cooler due to accumulation of the like.

JP 2010-31749 A

  However, in such a conventional failure diagnosis device for an EGR device, the failure diagnosis is actually started after the predetermined delay time has elapsed after the predetermined diagnosis condition is satisfied, and therefore, it takes a long time to complete the failure diagnosis. There was a problem of becoming.

By the way, in recent years, from the viewpoint of improving fuel efficiency, there are many vehicles in which so-called fuel cut is performed in which fuel supply to the internal combustion engine is stopped when the vehicle is decelerated. Such a failure diagnosis device for an EGR device mounted on a vehicle performs failure diagnosis of the EGR device during deceleration when fuel cut is being performed.
Therefore, when the failure diagnosis device for an EGR device described in Patent Document 1 is applied to a vehicle capable of performing the fuel cut as described above, the following problem occurs.

  That is, in the failure diagnosis device for an EGR device described in Patent Document 1, the exhaust gas in the exhaust passage is scavenged as the predetermined delay time elapses, but the exhaust gas remaining in the EGR passage is also scavenged. I can't. For this reason, in this failure diagnosis device for an EGR device, the exhaust gas remaining in the EGR passage flows into the intake passage at once when the EGR valve is fully opened after a predetermined delay time has elapsed.

  As described above, when the restart condition of the internal combustion engine, such as the accelerator being depressed, is satisfied at the start of the failure diagnosis in which a large amount of exhaust gas flows into the intake passage, a large amount of exhaust gas is introduced into the intake passage. In this state, the internal combustion engine is started. In such a case, since the exhaust gas concentration in the combustion chamber increases, normal ignition cannot be performed, and so-called engine stall may occur in which the internal combustion engine stops.

  Therefore, the present invention can complete the failure diagnosis of the EGR device earlier than the conventional one, and suppress the occurrence of engine stall when the internal combustion engine is restarted during the failure diagnosis of the EGR device. An object of the present invention is to provide a failure diagnosis device for an EGR device.

  According to a first aspect of the present invention, there is provided an EGR apparatus failure diagnosis apparatus that connects an intake passage and an exhaust passage of an internal combustion engine and recirculates a part of exhaust gas flowing through the exhaust passage to the intake passage. An EGR provided with a passage, an EGR valve that is provided in the EGR passage and adjusts the flow rate of the exhaust gas recirculated to the intake passage, and an EGR valve opening degree adjustment unit that adjusts the opening degree of the EGR valve An apparatus failure diagnosis apparatus, comprising: an intake parameter detection unit that detects an intake parameter representing the state of air in the intake passage; and the EGR valve opening degree on condition that a predetermined EGR diagnosis condition is satisfied A failure diagnosis unit that opens the EGR valve to a target opening degree that is targeted by the adjustment unit and performs a failure diagnosis of the EGR device, and the EGR valve opening degree adjustment unit includes the EGR valve After the disconnection condition is satisfied, the maximum opening of the EGR valve is set to a minute opening smaller than the target opening until a predetermined duration elapses, and the maximum opening of the EGR valve is set after the lapse of the duration. The target opening degree is set, and the failure diagnosis unit performs the failure diagnosis based on the intake parameter until the duration time elapses and the intake parameter after the duration time elapses. .

  As a second aspect of the present invention, the EGR valve opening adjustment unit sets the maximum opening of the EGR valve to zero until a predetermined fully closed time elapses after the lapse of the continuation time. The maximum opening degree of the EGR valve is set as the target opening degree after the lapse of the closing time, and the failure diagnosing unit sets the intake parameter when the maximum opening degree of the EGR valve is zero and the intake air after the full closing time period The failure diagnosis is preferably performed based on the parameters.

  A third aspect of the present invention includes a time setting unit that sets the duration, and the time setting unit sets the duration as the value of the intake parameter detected by the intake parameter detection unit increases. It is preferable to shorten it.

  As a fourth aspect of the present invention, it is preferable that the EGR valve opening degree adjusting unit increases the opening degree of the EGR valve to the minute opening degree at a predetermined rate after the EGR diagnosis condition is satisfied.

  As a fifth aspect of the present invention, the EGR valve opening degree adjusting unit maintains the opening degree of the EGR valve at the minute opening degree until the duration time elapses after the EGR diagnosis condition is satisfied. preferable.

  As a sixth aspect of the present invention, it is preferable that the intake parameter detection unit includes an intake pressure detection unit that detects an intake pressure that is a pressure of intake air of the internal combustion engine as the intake parameter.

  As a seventh aspect of the present invention, it is preferable that the intake parameter detection unit includes an intake air amount detection unit that detects an intake air amount of the internal combustion engine as the intake parameter.

  Thus, according to the first aspect described above, the failure diagnosis is started by opening the EGR valve by a minute opening immediately after the EGR diagnosis condition is satisfied. Therefore, the scavenging of the exhaust passage is performed after the EGR diagnosis condition is satisfied as in the prior art. The failure diagnosis of the EGR device can be completed at an early stage without providing time for performing the operation.

  Further, after the EGR diagnosis condition is satisfied, the maximum opening of the EGR valve is set to a minute opening smaller than the target opening until the continuation time elapses, so that the exhaust gas remaining in the EGR passage starts the failure diagnosis. Sometimes, a large amount can be prevented from flowing into the intake passage. Therefore, since the exhaust gas concentration in the combustion chamber is kept low even at the time of starting the failure diagnosis, for example, even if it is necessary to restart the internal combustion engine immediately after the failure diagnosis starts, the engine stall occurs at the time of the restart. Can be suppressed.

  According to the second aspect, since the intake parameter when the EGR valve is closed is used for at least one of the intake parameters detected when performing the failure diagnosis of the EGR device, the intake parameter is detected when the intake parameter is detected. It is possible to avoid the influence of fluctuations in the rotational speed and load of the internal combustion engine. Therefore, it is possible to suppress variations in intake parameters used at the time of failure diagnosis of the EGR device, and improve the accuracy of failure diagnosis.

  According to the third aspect, the duration after the EGR diagnosis condition is satisfied is shortened as the value of the intake parameter is larger. Here, when the internal combustion engine is operating such that the value of the intake parameter becomes large, scavenging of the exhaust gas in the EGR passage is completed quickly. Therefore, when the scavenging of the exhaust gas in the EGR passage is completed early, the duration after the EGR diagnosis condition is satisfied can be shortened. As a result, failure diagnosis of the EGR device can be completed early according to the operating state of the internal combustion engine.

  According to the fourth aspect, after the EGR diagnosis condition is satisfied, the opening degree of the EGR valve is increased at a predetermined rate to a minute opening degree smaller than the target opening degree, so that the exhaust gas remaining in the EGR passage It is possible to prevent a large amount of gas from flowing into the intake passage at the start of failure diagnosis.

  According to the fifth aspect described above, since the opening degree of the EGR valve is maintained at a minute opening degree smaller than the target opening degree after the EGR diagnosis condition is satisfied until the duration time elapses, the EGR valve remains in the EGR passage. It is possible to prevent a large amount of exhaust gas from flowing into the intake passage at the start of failure diagnosis.

  According to the sixth aspect described above, failure diagnosis of the EGR device can be performed appropriately based on, for example, the intake pressure that changes due to clogging in the EGR passage or failure of the EGR valve.

  According to the seventh aspect described above, failure diagnosis of the EGR device can be performed appropriately based on, for example, the intake air amount that changes due to clogging in the EGR passage or failure of the EGR valve.

FIG. 1 is a schematic configuration diagram showing a main part of a vehicle equipped with a failure diagnosis device for an EGR device according to a first embodiment of the present invention. FIG. 2 is a flowchart showing a flow of failure diagnosis of the EGR device executed by the ECU according to the first embodiment of the present invention. FIG. 3 is a time chart showing an operation at the time of failure diagnosis of the EGR device according to the first embodiment of the present invention. FIG. 4 is a time chart showing an operation when returning from the fuel cut control during the failure diagnosis of the EGR device according to the first embodiment of the present invention. FIG. 5 is a flowchart showing a flow of failure diagnosis of the EGR device executed by the ECU according to the second embodiment of the present invention. FIG. 6 is a time chart showing the operation at the time of failure diagnosis of the EGR device according to the second embodiment of the present invention. FIG. 7 is a time chart showing the operation when returning from the fuel cut control during the failure diagnosis of the EGR device according to the second embodiment of the present invention. FIG. 8 is a flowchart showing a flow of failure diagnosis of the EGR device executed by the ECU according to the third embodiment of the present invention. FIG. 9 is a time chart showing an operation at the time of failure diagnosis of the EGR device according to the third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
First, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a vehicle 1 according to this embodiment includes an engine 2 as an internal combustion engine, an intake device 3, an exhaust device 4, an EGR device 5, and an ECU (Engine Control Unit) 10. It is configured.

The engine 2 is composed of, for example, an in-line four-cylinder gasoline engine, and includes a fuel supply device and an ignition device (not shown). The fuel supply device has a fuel injection valve corresponding to each cylinder. The engine 2 is not limited to a gasoline engine but may be a diesel engine, or may be a V-type engine or the like without being limited to an in-line four cylinder.
Further, the engine 2 includes a water temperature sensor 21 that detects the temperature of the cooling water, a cam angle sensor 22 that detects a rotation angle of a camshaft (not shown), and a crank angle sensor 23 that detects a rotation angle of a crankshaft (not shown). Is provided.

The intake device 3 is connected to the engine 2 and includes an intake pipe 31 and an intake manifold 32. The intake pipe 31 is a pipe for taking in fresh air from the outside of the vehicle 1 through the intake manifold 32 and introducing it into the engine 2.
An intake passage 31 a is formed in the intake pipe 31. An air cleaner 33, an intake air amount sensor 34, a throttle valve 35, and an intake pressure sensor 36 are provided on the intake passage 31a from the upstream side in the inflow direction of fresh air.

The air cleaner 33 cleans fresh air taken from the outside of the vehicle 1. The intake air amount sensor 34 is a sensor that detects the amount of fresh air introduced into the engine 2, that is, the intake air amount. That is, the intake air amount sensor 34 constitutes an intake air amount detection unit according to the present invention.
The throttle valve 35 adjusts the amount of intake air by adjusting the opening degree of the throttle motor 35a. The intake pressure sensor 36 is a sensor that detects an intake pressure Pin that is the pressure of intake air. The intake pressure sensor 36 according to the present embodiment constitutes an intake pressure detection unit according to the present invention.
Here, the intake air amount sensor 34 and the intake pressure sensor 36 described above detect the intake air amount and the intake pressure Pin, respectively, as intake parameters representing the state of air in the intake passage 31a. Therefore, the intake air amount sensor 34 and the intake pressure sensor 36 according to the present embodiment constitute an intake parameter detection unit according to the present invention.

The exhaust device 4 is connected to the engine 2 and includes an exhaust pipe 41, an exhaust manifold 42, a catalyst device 43, and a silencer 44.
The exhaust pipe 41 is a pipe for taking in the exhaust gas discharged from the engine 2 and discharging it through the exhaust manifold 42 to the outside of the vehicle 1. An exhaust passage 41 a is formed in the exhaust pipe 41.

The catalyst device 43 is provided on an exhaust passage 41 a between the exhaust manifold 42 and the silencer 44. The catalyst device 43 purifies harmful gases such as carbon monoxide (CO), hydrocarbons (CH) and nitrogen oxides (NOx) in exhaust gas into carbon dioxide (CO ₂ ) and water (H ₂ O). For example, it is constituted by a three-way catalyst.
The catalyst device 43 is provided with an air-fuel ratio sensor 45 and an O ₂ sensor 46. The air-fuel ratio sensor 45 is a sensor that detects the air-fuel ratio (A / F) in the exhaust gas introduced into the catalyst device 43. The air-fuel ratio sensor 45 is an oxygen sensor having an output characteristic linear with respect to the air-fuel ratio. The O ₂ sensor 46 is an oxygen sensor having an output characteristic in which the output suddenly changes between the rich side and the lean side with respect to the air / fuel ratio with reference to the stoichiometric air / fuel ratio.

  The silencer 44 is a so-called muffler that suppresses noise generated by exhaust gas discharged from the exhaust device 4 to the outside of the vehicle 1.

The EGR device 5 is a so-called exhaust gas recirculation device that recirculates part of the exhaust gas to the intake side and introduces it again into the combustion chamber of the engine 2. When a part of the exhaust gas is introduced into the combustion chamber by the EGR device 5, the combustion temperature is lowered, the generation of nitrogen oxides (NOx) in the combustion chamber is suppressed, and the exhaust emission is improved.
The EGR device 5 includes an EGR pipe 51 in which an EGR passage 51 a is formed, an EGR valve 52, and an EGR cooler 53.

  The EGR pipe 51 is provided so as to connect the intake pipe 31 and the exhaust pipe 41. The EGR passage 51a is a passage that connects the intake passage 31a and the exhaust passage 41a and returns a part of the exhaust gas flowing through the exhaust passage 41a to the intake passage 31a.

  The EGR valve 52 is provided on the EGR passage 51a and adjusts the flow rate of the exhaust gas recirculated to the intake passage 31a. The EGR valve 52 is connected to the ECU 10 and its opening degree is controlled by the ECU 10. Specifically, as described later, the opening degree of the EGR valve 52 is adjusted by the EGR valve opening degree adjustment unit 102 of the ECU 10. Therefore, the EGR valve opening adjustment unit 102 is configured as a part of the EGR device 5.

  The EGR cooler 53 is provided on the EGR passage 51a and cools the exhaust gas that recirculates the EGR passage 51a toward the intake passage 31a.

The ECU 10 includes, for example, a microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM and performs signal processing according to a program stored in advance in the ROM. It is like that. Various control constants and various maps are stored in advance in the ROM.
Further, on the input side of the ECU 10, various sensors such as the water temperature sensor 21, the cam angle sensor 22, the crank angle sensor 23, the intake air amount sensor 34, the intake pressure sensor 36, the air-fuel ratio sensor 45, and the O ₂ sensor 46 described above. Is connected. On the other hand, various devices such as the throttle valve 35, the EGR valve 52, a fuel injection valve, and a spark plug (not shown) are connected to the output side of the ECU 10.

  Further, the ECU 10 includes a fuel cut control unit 101, an EGR valve opening degree adjustment unit 102, a failure diagnosis unit 103, and a time setting unit 104.

The fuel cut control unit 101 stops fuel supply to the engine 2, that is, stops fuel injection from the fuel injection valve on condition that a predetermined fuel cut condition is satisfied when the vehicle 1 decelerates. Control is to be executed.
Here, examples of the fuel cut condition include that the throttle opening is not more than a specified value, the vehicle speed is not less than a specified value, and the engine speed is not less than a specified value. Further, when the fuel cut control unit 101 determines that all of these conditions are satisfied, the F / C flag is set to ON.

The EGR valve opening adjustment unit 102 controls the opening of the EGR valve 52 in accordance with the operating state of the engine 2 and adjusts the flow rate of exhaust gas recirculated toward the intake passage 31a, that is, the EGR amount. ing. This EGR amount is set according to an EGR map stored in advance in the ROM of the ECU 10. The EGR map determines the EGR amount using the engine speed and the engine load as parameters, and is experimentally obtained in advance and stored in the ROM.
Here, the EGR valve opening degree adjusting unit 102 is described later without referring to the above-described EGR map when fuel cut control is being executed and failure diagnosis of the EGR device 5 described later is being performed. The opening degree of the EGR valve 52 is adjusted based on conditions and the like.

The failure diagnosis unit 103 performs failure diagnosis of the EGR device 5 by opening the EGR valve 52 to a target opening degree by the EGR valve opening degree adjustment unit 102 on condition that a predetermined EGR diagnosis condition is satisfied. It is like that.
When the failure diagnosis is performed by the failure diagnosis unit 103, the opening degree of the EGR valve 52 is controlled as follows by the EGR valve opening degree adjustment unit 102 described above.

  That is, the EGR valve opening degree adjustment unit 102 sets the maximum opening degree of the EGR valve 52 to a minute opening degree smaller than the above-described target opening degree until the continuation time T1 to be described later elapses after the EGR diagnosis condition is satisfied. The maximum opening degree of the EGR valve 52 is set to the above-mentioned target opening degree after the continuation time T1 has elapsed.

  Further, the EGR valve opening adjustment unit 102 adjusts the maximum opening of the EGR valve 52 to a very small opening. After the EGR diagnosis condition is satisfied, the opening of the EGR valve 52 is gradually reduced to the very small opening, that is, Increasing at a predetermined rate. As a result, the EGR valve 52 is gradually opened after the EGR diagnosis condition is satisfied, and is opened at a minute opening when the duration T1 is reached.

  On the other hand, the failure diagnosis unit 103 performs failure diagnosis of the EGR device 5 based on the intake pressure Pin1 until the continuation time T1 elapses and the intake pressure Pin2 after the continuation time T1 elapses.

  Specifically, the failure diagnosis unit 103 determines whether or not the pressure difference between the intake pressure Pin1 and the intake pressure Pin2, that is, the value obtained by subtracting the intake pressure Pin1 from the intake pressure Pin2 is greater than a predetermined threshold Pth. It is supposed to be. If the EGR valve 52 is broken or the EGR passage 51a is clogged, there will be no pressure difference between the intake pressure Pin1 and the intake pressure Pin2, or a small pressure difference. Therefore, the failure diagnosis unit 103 determines that the EGR device 5 has a failure when it is determined that the value obtained by subtracting the intake pressure Pin1 from the intake pressure Pin2 is smaller than the threshold value Pth. Thus, the failure diagnosis unit 103 can appropriately perform failure diagnosis of the EGR device 5 based on the intake pressure Pin that changes due to, for example, clogging in the EGR passage 51a or failure of the EGR valve 52.

In the present embodiment, the average value of the intake pressure Pin measured a predetermined number of times until the duration T1 elapses after the EGR diagnosis condition is satisfied is used as the above-described intake pressure Pin1.
The intake pressure Pin2 is measured at a predetermined time interval after the continuation time T1 has elapsed. The intake pressure Pin2 may be an average value of a plurality of measurement values measured at a predetermined time interval, or may be a minimum value of the plurality of measurement values.

  Here, the EGR diagnosis condition is a condition that defines an operation state suitable for performing a failure diagnosis of the EGR device 5, for example, “the fuel cut control is being executed”, “the throttle opening is zero. There are conditions such as “there is” and “the engine rotational speed is within a predetermined rotational speed range”. If the EGR valve opening adjustment unit 102 determines that all of these conditions are satisfied, the EGR valve opening adjustment unit 102 sets the EGR diagnosis flag to ON. Note that the above-described EGR diagnosis condition is an example, and is not limited thereto, and may satisfy any one of the above conditions, or may be a condition other than the above.

  The minute opening is, for example, that air having a flow rate sufficient to scavenge the exhaust gas remaining in the EGR passage 51a during the above-described duration T1 is returned from the exhaust passage 41a to the intake passage 31a. The opening degree is such that a large amount of exhaust gas does not flow into the intake passage 31a at a stretch.

  Here, the failure diagnosis unit 103 can perform more accurate failure diagnosis as the pressure difference between the intake pressure Pin1 and the intake pressure Pin2 is larger. Therefore, the above-mentioned target opening is an opening that can recirculate air from the exhaust passage 41a to the intake passage 31a to such an extent that a pressure difference that can accurately perform failure diagnosis of the EGR device 5 is obtained. is there.

  Further, the duration T1 is a time that the scavenging of the exhaust gas in the EGR passage 51a is completed by the air recirculated in the process of gradually opening the EGR valve 52 to a very small opening after the EGR diagnosis condition is satisfied. Is set.

  The time setting unit 104 sets the above-described duration T1 based on a predetermined time setting map. Specifically, the time setting unit 104 shortens the duration T1 as the intake pressure Pin detected by the intake pressure sensor 36 increases. If the intake pressure Pin before the start of failure diagnosis of the EGR device 5 is large, the negative pressure in the intake passage 31a is large. Therefore, the exhaust gas recirculated from the EGR passage 51a to the intake passage 31a is smaller than when the negative pressure is small. The flow rate per unit time increases. For this reason, when the intake pressure Pin is large, scavenging of the exhaust gas in the EGR passage 51a is completed early. Therefore, the time setting unit 104 can shorten the duration T1 as the intake pressure Pin is larger as described above.

  The time setting map is stored in the ROM of the ECU 10 by previously experimentally obtaining the relationship between the intake pressure Pin and the duration T1. In the present embodiment, the duration T1 is set based on the intake pressure Pin, but the duration T1 may be set based on the intake air amount. In this case, the time setting unit 104 shortens the duration time T1 as the intake air amount increases.

Next, with reference to FIG. 2, the failure diagnosis process of the EGR device 5 executed by the failure diagnosis unit 103 of the ECU 10 according to the present embodiment will be described.
Note that each process of the failure diagnosis is executed in detail by the fuel cut control unit 101, the EGR valve opening adjustment unit 102, the failure diagnosis unit 103, and the time setting unit 104 that the ECU 10 has. 2, the subject of each process is described as the ECU 10.

  As shown in FIG. 2, first, the ECU 10 determines whether or not fuel cut control is being executed, that is, whether or not fuel cut is being performed, based on the F / C flag (step S1). When it is determined that the fuel cut is not being performed, the ECU 10 repeatedly executes the process of this step until the fuel cut is being performed.

  On the other hand, when it is determined that the fuel cut is in progress, the ECU 10 determines whether or not the EGR diagnosis condition is satisfied based on the EGR diagnosis flag (step S2). When it is determined that the EGR diagnosis condition is not satisfied, the ECU 10 repeatedly executes the processes of step S1 and step S2 until the EGR diagnosis condition is satisfied.

  On the other hand, when the ECU 10 determines that the EGR diagnosis condition is satisfied during the fuel cut, the ECU 10 sets the maximum opening of the EGR valve 52 to a minute opening (step S3). Thereafter, the ECU 10 gradually opens the EGR valve 52 to the minute opening set in step S3 (step S4).

  Next, the ECU 10 measures the intake pressure Pin at a predetermined time interval, and uses the average value thereof as the intake pressure Pin1 (step S5).

  Next, the ECU 10 determines whether or not the duration time T1 has elapsed after the EGR diagnosis condition is satisfied (step S6). When it is determined that the duration time T1 has not elapsed, the ECU 10 repeatedly executes each process from step S4 until the duration time T1 has elapsed.

  On the other hand, if the ECU 10 determines that the duration T1 has elapsed, the ECU 10 opens the EGR valve 52 to the target opening (step S7). Thereafter, the ECU 10 measures the intake pressure Pin2 (step S8).

  Next, the ECU 10 compares the intake pressure differential pressure ΔPin (= Pin2-Pin1), which is a value obtained by subtracting the intake pressure Pin1 from the intake pressure Pin2, with a predetermined threshold value Pth (step S9). Thereafter, the ECU 10 determines whether or not the intake pressure differential pressure ΔPin is larger than the threshold value Pth (step S10). If the ECU 10 determines that the intake pressure differential pressure ΔPin is greater than the threshold value Pth, the ECU 10 determines that the EGR device 5 is not broken and performs normal determination (step S11), and ends the present process.

  On the other hand, if the ECU 10 determines that the intake pressure differential pressure ΔPin is not larger than the threshold value Pth, that is, is smaller, the ECU 10 determines that the possibility that the EGR device 5 is malfunctioning is high and performs abnormality determination (step) S12), this process is terminated. When the abnormality determination is made, the ECU 10 notifies the driver of the failure of the EGR device 5 by turning on a warning light or the like provided in the passenger compartment, for example.

Next, with reference to FIG. 3, the operation at the time of failure diagnosis of the EGR device 5 according to the present embodiment will be described.
As shown in FIG. 3, in the vehicle 1, when the EGR diagnosis condition is satisfied during the fuel cut and the EGR diagnosis flag is turned ON, the opening degree of the EGR valve 52 is gradually increased to a minute opening degree. At this time, the exhaust gas concentration in the intake passage 31a gradually increases immediately after opening the EGR valve 52, and then gradually decreases as the opening degree of the EGR valve 52 increases. At this time, the maximum value of the exhaust gas concentration in the intake passage 31a is greatly reduced as compared with the conventional case where the EGR valve 52 is immediately opened from the start of failure diagnosis to the target opening degree. ing.

  Thereafter, when the duration time T1 elapses, the EGR valve 52 is opened to the target opening degree. At this time, the engine 2 has stopped combustion. Accordingly, fresh air introduced from the intake passage 31a is discharged to the exhaust passage 41a. Further, the exhaust gas in the EGR passage 51a is scavenged until the duration time T1 elapses. Therefore, even if the EGR valve 52 is opened to the target opening, only fresh air in the exhaust passage 41a is recirculated to the intake passage 31a. As a result, after the EGR valve 52 is opened at the target opening, the exhaust gas concentration in the intake passage 31a is maintained in a reduced state.

  Next, the ECU 10 performs a failure diagnosis of the EGR device 5 based on the intake pressure Pin1 until the duration T1 elapses and the intake pressure Pin2 after the duration T1 elapses. After the failure diagnosis is completed, the EGR valve 52 is fully closed again and the EGR diagnosis flag is turned off.

Next, with reference to FIG. 4, the operation when returning from the fuel cut control during the failure diagnosis of the EGR device 5 according to the present embodiment will be described.
As shown in FIG. 4, for example, after the EGR diagnosis condition is satisfied and before returning from the fuel cut control before the lapse of time T <b> 1, the exhaust gas recirculated into the intake passage 31 a and the outside of the vehicle 1 are introduced. The engine 2 is burned by fresh air. At this time, in the present embodiment, as shown in FIG. 3, the exhaust gas concentration in the intake passage 31a until the continuation time T1 elapses is greatly reduced, so that the return from the fuel cut control as described above is performed. The engine 2 can be combusted without any problems. Therefore, since the combustion state of the engine 2 is not deteriorated, the occurrence of engine stall when the engine 2 is restarted with the return from the fuel cut control is suppressed.

  As described above, the failure diagnosis device for the EGR device 5 according to the present embodiment starts the failure diagnosis by opening the EGR valve 52 by a minute opening immediately after the EGR diagnosis condition is satisfied. The failure diagnosis of the EGR device 5 can be completed at an early stage without providing a time for scavenging the exhaust passage 41a after the above.

  Further, the failure diagnosis device for the EGR device 5 according to the present embodiment sets the maximum opening of the EGR valve 52 to a minute opening smaller than the target opening until the duration T1 elapses after the EGR diagnosis condition is satisfied. Thus, it is possible to prevent a large amount of exhaust gas remaining in the EGR passage 51a from flowing into the intake passage 31a at the start of failure diagnosis. Therefore, since the exhaust gas concentration in the combustion chamber is kept low even when the failure diagnosis is started, for example, even when the engine 2 needs to be restarted with the return from the fuel cut control immediately after the failure diagnosis starts, The occurrence of engine stall at the time of restart can be suppressed.

  Further, the failure diagnosis device for the EGR device 5 according to the present embodiment shortens the duration T1 after the EGR diagnosis condition is satisfied as the intake pressure Pin increases. Here, when the engine 2 is operating such that the intake pressure Pin becomes large, scavenging of the exhaust gas in the EGR passage 51a is completed quickly. Therefore, when the scavenging of the exhaust gas in the EGR passage 51a is completed early, the duration T1 after the EGR diagnosis condition is satisfied can be shortened. As a result, the failure diagnosis device for the EGR device 5 according to the present embodiment can complete the failure diagnosis for the EGR device 5 at an early stage according to the operating state of the engine 2.

  Furthermore, the failure diagnosis device for the EGR device 5 according to the present embodiment increases the opening of the EGR valve 52 at a predetermined rate to a minute opening smaller than the target opening after the EGR diagnosis condition is satisfied. It is possible to prevent the exhaust gas remaining in 51a from flowing in a large amount into the intake passage 31a at the start of failure diagnosis.

  In the present embodiment, the intake pressure Pin is detected by the intake pressure sensor 36, but the intake pressure Pin may be calculated based on the intake air amount detected by the intake air amount sensor 34, for example. . In this case, the ECU 10 can calculate the intake pressure Pin from the intake air amount, for example, by referring to a map in which the relationship between the intake air amount and the intake pressure Pin is experimentally obtained in advance. In this case, the vehicle 1 may not be equipped with the intake pressure sensor 36.

  In the present embodiment, the failure diagnosis of the EGR device 5 is performed based on the change of the intake pressure Pin. However, the failure diagnosis of the EGR device 5 may be performed based on the change of the intake air amount. Specifically, the failure diagnosis unit 103 determines whether or not the difference between the intake air amount until the continuation time T1 elapses and the intake air amount after the continuation time T1 elapses is greater than a predetermined threshold value. Thus, failure diagnosis of the EGR device 5 is performed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
The present embodiment is different from the above-described first embodiment in the processing content of step S14 in the failure diagnosis processing of the EGR device 5, but the other configuration and processing content are the same as those of the first embodiment. Therefore, in the following, description of the same configuration and processing contents as those of the first embodiment will be omitted, and only portions different from those of the first embodiment will be described.

  In the present embodiment, the EGR valve opening adjustment unit 102 of the ECU 10 opens the EGR valve 52 not gradually until the minute opening after the EGR diagnosis condition is satisfied, but immediately until the duration T1 elapses. The opening is maintained at a very small opening.

  As shown in FIG. 5, in the process of step S14 for failure diagnosis of the EGR device 5, the ECU 10 opens the EGR valve 52 immediately rather than gradually until the minute opening set in step S13. In FIG. 5, the processes other than step S13 are the same as steps S1, S2 and steps S4 to S12 of the first embodiment, respectively.

  Further, as shown in FIG. 6, in the vehicle 1 according to the present embodiment, when the EGR diagnosis flag is turned ON during the fuel cut, the opening degree of the EGR valve 52 is immediately increased to a minute opening degree. The characteristics of the exhaust gas concentration in the intake passage 31a at this time are the same as in the first embodiment, and the maximum value is greatly reduced as in the first embodiment compared to the conventional one. In addition, since it is the same as that of 1st Embodiment about the effect | action after this, description is abbreviate | omitted.

  Further, as shown in FIG. 7, in this embodiment as well, as in the first embodiment, the combustion state of the engine 2 deteriorates even when returning from the fuel cut control during the failure diagnosis of the EGR device 5. There is no. Therefore, the occurrence of engine stall when the engine 2 is restarted with the return from the fuel cut control is suppressed.

As described above, the failure diagnosis device for the EGR device 5 according to the present embodiment has the following effects in addition to the effects in the first embodiment described above.
That is, the failure diagnosis device for the EGR device 5 according to the present embodiment maintains the opening of the EGR valve 52 at a minute opening smaller than the target opening until the duration T1 elapses after the EGR diagnosis condition is satisfied. Thus, it is possible to prevent a large amount of exhaust gas remaining in the EGR passage 31a from flowing into the intake passage 31a at the start of failure diagnosis.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.
This embodiment is different from the first embodiment described above in that a process of closing the EGR valve 52 is once added after the lapse of the duration T1 in the fault diagnosis process of the EGR device 5, but other configurations and processing contents Is the same as in the first embodiment. Therefore, in the following, description of the same configuration and processing contents as those of the first embodiment will be omitted, and only portions different from those of the first embodiment will be described.

  In the present embodiment, the EGR valve opening adjustment unit 102 of the ECU 10 increases the maximum opening of the EGR valve 52 until a predetermined full-close time T2 elapses after the continuation time T1 elapses after the EGR diagnosis condition is satisfied. It is supposed to be zero. Thereby, the EGR valve 52 is changed from the open state of the minute opening to the fully closed state at the timing when the duration time T1 has elapsed. The fully closed state of the EGR valve 52 is maintained until the fully closed time T2 elapses.

  In addition, the EGR valve opening degree adjusting unit 102 determines that the above-described fully closed time T2 has elapsed or that the total time T3 obtained by adding the fully closed time T2 to the continuous time T1 has elapsed after the EGR diagnosis condition is satisfied. In addition, the EGR valve 52 is opened to the target opening. The fully closed time T2 is a time from when the EGR valve 52 is fully closed to when the EGR valve 52 is opened to the target opening degree.

  On the other hand, the failure diagnosis unit 103 performs failure diagnosis of the EGR device 5 based on the intake pressure Pin1 when the opening of the EGR valve 52 is zero and the intake pressure Pin2 after the full-close time T2. . Note that the failure diagnosis method based on the intake pressure Pin1 and the intake pressure Pin2 in the present embodiment is the same as that in the first embodiment, and thus the description thereof is omitted here.

  However, in the present embodiment, after the opening degree of the EGR valve 52 becomes zero, the average value of the intake pressure Pin measured for a predetermined number of times until the fully closed time T2 elapses is used. The atmospheric pressure Pin1 was used.

  The intake pressure Pin2 is measured at a predetermined time interval after the fully closed time T2 has elapsed. The intake pressure Pin2 may be an average value of a plurality of measurement values measured at a predetermined time interval, or may be a minimum value of the plurality of measurement values.

  Next, with reference to FIG. 8, the failure diagnosis process of the EGR device 5 executed by the failure diagnosis unit 103 of the ECU 10 according to the present embodiment will be described. In FIG. 8 as well, the subject of each process is described as the ECU 10 as in the first embodiment.

  As shown in FIG. 8, first, the ECU 10 determines whether or not a fuel cut is in progress based on the F / C flag (step S31). When it is determined that the fuel cut is not being performed, the ECU 10 repeatedly executes the process of this step until the fuel cut is being performed.

  On the other hand, when it is determined that the fuel cut is in progress, the ECU 10 determines whether or not the EGR diagnosis condition is satisfied based on the EGR diagnosis flag (step S32). When it is determined that the EGR diagnosis condition is not satisfied, the ECU 10 repeatedly executes the processes of step S31 and step S32 until the EGR diagnosis condition is satisfied.

  On the other hand, when the ECU 10 determines that the EGR diagnosis condition is satisfied during the fuel cut, the ECU 10 sets the maximum opening of the EGR valve 52 to a minute opening (step S33). Thereafter, the ECU 10 gradually opens the EGR valve 52 to the minute opening set in step S33 (step S34).

Next, the ECU 10 determines whether or not the duration time T1 has elapsed after the EGR diagnosis condition is satisfied (step S35). If it is determined that the duration time T1 has not elapsed, the ECU 10 repeatedly executes the process of step S35 until the duration time T1 has elapsed.
On the other hand, when it is determined that the duration time T1 has elapsed, the ECU 10 closes the EGR valve 52, that is, fully closes (step S36).

  Next, after the EGR valve 52 is fully closed, the ECU 10 measures the intake pressure Pin at predetermined time intervals until the fully closed time T2 elapses, and calculates the average value of these values as the intake pressure Pin1. (Step S37).

Thereafter, the ECU 10 determines whether or not the fully closed time T2 has elapsed (step S38). When it is determined that the fully closed time T2 has not elapsed, the ECU 10 repeatedly executes the process of step S38 until the fully closed time T2 has elapsed.
On the other hand, when the ECU 10 determines that the fully closed time T2 has elapsed, the ECU 10 opens the EGR valve 52 to the target opening (step S39). Thereafter, the ECU 10 measures the intake pressure Pin2 (step S40).

  Next, the ECU 10 compares the intake pressure differential pressure ΔPin (= Pin2-Pin1), which is a value obtained by subtracting the intake pressure Pin1 from the intake pressure Pin2, with a predetermined threshold value Pth (step S41). Thereafter, the ECU 10 determines whether or not the intake pressure differential pressure ΔPin is greater than the threshold value Pth (step S42). When the ECU 10 determines that the intake pressure differential pressure ΔPin is larger than the threshold value Pth, the ECU 10 determines that the EGR device 5 is not broken and performs normal determination (step S43), and ends the present process.

  On the other hand, if the ECU 10 determines that the intake pressure differential pressure ΔPin is not larger than the threshold value Pth, that is, is smaller, the ECU 10 determines that the possibility that the EGR device 5 is malfunctioning is high and performs abnormality determination (step) S44), this process is terminated. When the abnormality determination is made, the ECU 10 notifies the driver of the failure of the EGR device 5 by turning on a warning light or the like provided in the passenger compartment, for example.

Next, with reference to FIG. 9, the operation | movement at the time of the failure diagnosis of the EGR apparatus 5 which concerns on this embodiment is demonstrated.
As shown in FIG. 9, in the vehicle 1 according to the present embodiment, when the EGR diagnosis condition is satisfied during the fuel cut and the EGR diagnosis flag is turned ON, the opening degree of the EGR valve 52 is gradually increased to a minute opening degree. The At this time, the exhaust gas concentration in the intake passage 31a gradually increases immediately after opening the EGR valve 52, and then gradually decreases as the opening degree of the EGR valve 52 increases. At this time, the maximum value of the exhaust gas concentration in the intake passage 31a is greatly reduced as compared with the conventional case where the EGR valve 52 is immediately opened from the start of failure diagnosis to the target opening degree. ing.

  Thereafter, when the duration time T1 elapses, the EGR valve 52 is once closed. The fully closed state of the EGR valve 52 is continued until the fully closed time T2 elapses. Thereafter, after the EGR valve 52 is closed, when the fully closed time T2 elapses or when the total time T3 elapses after the EGR diagnosis condition is satisfied, the EGR valve 52 is opened to the target opening degree.

  At this time, the engine 2 has stopped combustion. Accordingly, fresh air introduced from the intake passage 31a is discharged to the exhaust passage 41a. Further, the exhaust gas in the EGR passage 51a is scavenged until the duration time T1 elapses. Therefore, even if the EGR valve 52 is opened to the target opening, only fresh air in the exhaust passage 41a is recirculated to the intake passage 31a. As a result, after the EGR valve 52 is opened at the target opening, the exhaust gas concentration in the intake passage 31a is maintained in a reduced state.

  Next, the ECU 10 performs a failure diagnosis of the EGR device 5 based on the intake pressure Pin1 during the fully closed time T2 and the intake pressure Pin2 after the fully closed time T2 has elapsed. At this time, for example, at the time of a blockage abnormality in which the EGR passage 51a is clogged, as shown by a broken line in the figure, the intake pressure Pin2 is greatly reduced compared to the normal time shown by a solid line Become. For this reason, when the obstruction is abnormal, the intake pressure differential pressure ΔPin is also lower than the threshold value Pth as indicated by a broken line in the figure. After the failure diagnosis is completed, the EGR valve 52 is fully closed again and the EGR diagnosis flag is turned off.

As described above, the failure diagnosis device for the EGR device 5 according to the present embodiment has the following effects in addition to the effects in the first embodiment described above.
That is, the failure diagnosis device for the EGR device 5 according to the present embodiment uses the intake pressure Pin1 when the EGR valve 52 is closed for at least one of the intake pressure Pins detected when performing failure diagnosis of the EGR device 5. Therefore, when detecting the intake pressure Pin1, it is possible to avoid the influence of the rotational speed fluctuation and load fluctuation of the engine 2. Therefore, the failure diagnosis device for the EGR device 5 according to the present embodiment can suppress variations in the intake pressure Pin used when diagnosing the failure of the EGR device 5, and thus variations in the intake pressure differential pressure ΔPin, thereby improving the accuracy of the failure diagnosis. Can be made.

  In the present embodiment, the EGR valve opening adjustment unit 102 gradually opens the EGR valve 52 to a very small opening after the EGR diagnosis condition is satisfied. However, after the EGR diagnosis condition is satisfied, the EGR valve 52 is opened. It is good also as a structure which opens to a very small opening immediately, and maintains at a very small opening until continuation time T1 passes.

  While embodiments of the present invention have been disclosed as described above, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

1 vehicle 2 engine (internal combustion engine)
3 Intake device 4 Exhaust device 5 EGR device 10 ECU
31a Intake passage 34 Intake air amount sensor (intake parameter detection unit, intake air amount detection unit)
36 Intake pressure sensor (intake parameter detection unit, intake pressure detection unit)
41a Exhaust passage 51a EGR passage 52 EGR valve 101 Fuel cut control section 102 EGR valve opening adjustment section 103 Failure diagnosis section 104 Time setting section

Claims (7)

An EGR passage that communicates an intake passage and an exhaust passage of the internal combustion engine and returns a part of the exhaust gas flowing through the exhaust passage to the intake passage; and the exhaust gas that is provided in the EGR passage and is returned to the intake passage A failure diagnosis device for an EGR device, comprising: an EGR valve that adjusts a gas flow rate; and an EGR valve opening adjustment unit that adjusts the opening of the EGR valve,
An intake parameter detection unit for detecting an intake parameter representing the state of air in the intake passage;
A failure diagnosing unit that opens the EGR valve to a target opening degree that is a target by the EGR valve opening degree adjusting unit to perform a failure diagnosis of the EGR device on condition that a predetermined EGR diagnosis condition is satisfied; Prepared,
The EGR valve opening adjustment unit sets the maximum opening of the EGR valve to a minute opening smaller than the target opening until a predetermined duration elapses after the EGR diagnosis condition is satisfied, and the duration After the elapse of time, the maximum opening of the EGR valve is set as the target opening,
The failure diagnosis unit of the EGR apparatus, wherein the failure diagnosis unit performs the failure diagnosis based on the intake parameter until the duration time elapses and the intake parameter after the duration time elapses. The EGR valve opening adjustment unit sets the maximum opening of the EGR valve to zero until a predetermined fully-closed time elapses after the lapse of the duration, and sets the maximum EGR valve after the elapse of the fully-closed time. The opening is the target opening,
The failure diagnosis unit performs the failure diagnosis based on the intake parameter when the maximum opening of the EGR valve is zero and the intake parameter after the fully closed time has elapsed. A failure diagnosis device for the EGR device as described. A time setting unit for setting the duration;
The failure diagnosis device for an EGR device according to claim 1, wherein the time setting unit shortens the duration as the value of the intake parameter detected by the intake parameter detection unit increases.   4. The EGR valve opening degree adjusting unit increases the opening degree of the EGR valve at a predetermined rate to the minute opening degree after the EGR diagnosis condition is satisfied. The failure diagnosis device for an EGR device according to Item 1.   The said EGR valve opening adjustment part maintains the opening of the said EGR valve in the said minute opening until the said continuation time passes after the said EGR diagnostic conditions are satisfied. The failure diagnosis device for an EGR device according to any one of the above.   6. The intake pressure detection unit according to claim 1, wherein the intake parameter detection unit includes an intake pressure detection unit that detects an intake pressure that is a pressure of intake air of the internal combustion engine as the intake parameter. The fault diagnosis device for an EGR device according to the item. The said intake parameter detection part is comprised by the intake air amount detection part which detects the intake air amount of the said internal combustion engine as said intake parameter, The any one of Claims 1-5 characterized by the above-mentioned. EGR device failure diagnosis device.

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