JP5812413B2 - Exhaust gas recirculation device - Google Patents

Description

  The present invention adjusts the recirculation amount of exhaust gas in an exhaust gas recirculation device (hereinafter referred to as “EGR device” where appropriate) that purifies exhaust gas by recirculating exhaust gas of an internal combustion engine to the intake side. The present invention relates to a technical field of an exhaust gas recirculation device capable of detecting a failure such as sticking of an EGR valve.

  An internal combustion engine such as an engine may be equipped with a supercharger for compressing and supplying intake air in order to improve the intake charging efficiency into the combustion chamber and improve the output. In particular, in an exhaust supercharger, an exhaust turbine provided in an exhaust passage is rotationally driven by the flow energy of exhaust gas discharged from an engine, whereby a compressor provided in connection with the exhaust turbine is rotationally driven in an intake passage. Then, the intake air is compressed and supplied.

  There is also known an EGR device that promotes fuel efficiency and exhaust gas purification by returning a part of the exhaust gas discharged from the engine to the intake passage and returning it to the combustion chamber. When the exhaust gas is returned to the intake passage in the EGR device, the exhaust gas is supplied based on the pressure difference between the intake passage and the exhaust passage. In an EGR device applied to an engine having a supercharger in an intake passage, exhaust gas (EGR gas) in a high temperature and high pressure state is branched from an upstream exhaust passage of the exhaust turbine, and the downstream side intake passage of the supercharger The exhaust gas (EGR gas) branched from the downstream exhaust passage of the exhaust turbine is introduced into the upstream intake passage of the supercharger using the high pressure EGR device to be introduced and the negative pressure of the upstream intake passage of the supercharger. There is a low pressure EGR device.

  In such an EGR device, various failures occur, such as failure of an EGR valve for adjusting the amount of EGR gas introduced and clogging in the EGR passage due to accumulation of inclusions such as carbon contained in the EGR gas. There is. When such a failure occurs, it becomes impossible to introduce EGR gas into the intake passage, or the flow rate cannot be adjusted. Therefore, a device that detects such a failure of the EGR device early and reliably, A method has been proposed.

  For example, Patent Document 1 discloses an EGR device that compares the absolute value ΔT of the difference in intake air temperature before and after a predetermined transient state with a normal reference value ΔTbase to determine whether there is a failure in the EGR device. Yes.

JP 2008-223554 A

  In Patent Document 1, it is supposed that a failure can be detected based on the intake air temperature in a system using both a high pressure EGR device and a low pressure EGR device. However, even if the failure detection itself is possible in Patent Document 1, it cannot be determined whether the failure has occurred in the high-pressure EGR device or the low-pressure EGR device. In a system that uses both a high-pressure EGR device and a low-pressure EGR device, even if one of the EGR devices fails, a failure occurs by adjusting (covering) the supply amount of EGR gas with the other EGR device. Even at times, it is conceivable to suppress the deterioration of exhaust gas. However, such control is necessary on the premise that it is possible to determine which of the high pressure EGR and the low pressure EGR has failed, and is difficult to realize based on the technique of Patent Document 1.

  The present invention has been made in view of the above problems, and provides an exhaust gas recirculation device capable of accurately detecting which EGR device has failed in an engine including a high pressure EGR device and a low pressure EGR device. For the purpose.

In order to solve the above problems, an exhaust gas recirculation device according to the present invention is provided in an exhaust passage of an engine, and is provided in an exhaust turbine that is rotationally driven by exhaust gas flowing through the exhaust passage, and in an intake passage of the engine. A turbocharger having a compressor that compresses and supplies intake air to the engine by being driven to rotate in conjunction with the exhaust turbine; and the compressor in the intake passage from the upstream side of the exhaust turbine in the exhaust passage. High-pressure EGR passage for introducing exhaust gas further downstream, and high-pressure EGR means having high-pressure EGR flow rate control means for adjusting the amount of exhaust gas passing through the high-pressure EGR passage; A low pressure EGR passage for introducing exhaust gas from the downstream side of the exhaust turbine to the upstream side of the compressor of the intake passage; Low pressure EGR means having low pressure EGR flow rate control means for adjusting the amount of exhaust gas passing through the EGR passage, and the intake passage by controlling the high pressure EGR flow rate control means and the low pressure EGR flow rate control means An exhaust gas recirculation device comprising an EGR amount control means for adjusting the amount of exhaust gas recirculated to the intake air; and an intake air amount detection means for detecting an intake air amount upstream of a connecting portion of the low pressure EGR passage in the intake passage. A first oxygen concentration detecting means for detecting an oxygen concentration downstream of the connecting portion of the high pressure EGR passage in the intake passage; a downstream of the compressor in the intake passage; and the high pressure EGR passage. A second oxygen concentration detecting means for detecting an oxygen concentration upstream of the connecting portion of the exhaust gas, and an oxygen concentration downstream of the exhaust turbine in the exhaust passage. A third oxygen concentration detection means for detecting to obtain a measured value by the second oxygen concentration detector, with in comparison with the reference value the measured value performs failure determination of the low-pressure EGR device, A failure in which an actual measurement value is obtained by the intake air amount detection unit and the first to third oxygen concentration detection units, and a failure determination of the high pressure EGR unit is performed based on the low pressure EGR amount and the high pressure EGR amount calculated from the actual measurement value. Determining means, and the failure determining means makes a failure determination of the high pressure EGR means when it is determined that the low pressure EGR means is not broken .

  According to the present invention, either the high pressure EGR means or the low pressure EGR means can be obtained by comparing the measured values of the intake air amount detection means and the three oxygen concentration detection means or their calculated values with the normal values stored in advance. It is possible to accurately determine whether or not a failure has occurred.

Further, according to the present invention, the failure determining means, when the low-pressure EGR device is determined not to be faulty, intends line failure determination of the high-pressure EGR unit. The high pressure EGR means has a higher probability of failure because the EGR gas handled is at a higher temperature and pressure than the low pressure EGR means. Therefore, the failure determination in each EGR unit can be performed with high accuracy by performing the failure determination in the low-pressure EGR unit that is hard to stick first and determining the failure in the high-pressure EGR unit based on the determination result.

  More preferably, the failure determination means calculates a low pressure EGR amount based on actual measured values of the intake air amount detecting means and the second and third oxygen concentration detecting means, and the intake air amount detecting means and the first to first to A high pressure EGR amount is calculated based on an actual measurement value of the third oxygen concentration detection means, a high pressure EGR ratio is calculated based on the low pressure EGR amount and the high pressure EGR amount, and a normal high pressure EGR ratio stored in advance. It is preferable to make a failure determination of the high-pressure EGR means by comparing with the above. According to this, the low-pressure EGR amount and the high-pressure EGR amount are calculated by the intake air amount detection means and the three oxygen concentration detection means, and the calculated values are compared with the normal values stored in advance, whereby the high-pressure EGR means Failure determination can be performed with higher accuracy.

The failure determination means determines that the low pressure EGR means has failed and the amount of recirculation by the low pressure EGR means when the detection value of the second oxygen concentration detection means is equal to the atmospheric oxygen concentration. The high pressure EGR ratio may be calculated with zero as zero. According to this, by determining whether or not the detection value of the second oxygen concentration detection means is equal to the atmospheric oxygen concentration, for example, the low pressure EGR amount control means, which is a low pressure EGR valve, is firmly fixed in the closed state. It can be determined whether or not. When the low-pressure EGR amount control means is fixed in a completely closed state, the high-pressure EGR ratio can be calculated by setting the recirculation amount by the low-pressure EGR means to zero.
The failure determination means may perform the failure determination when exhaust gas is supplied from the low pressure EGR means and the high pressure EGR means to the intake passage.

  According to the present invention, either the high pressure EGR means or the low pressure EGR means can be obtained by comparing the measured values of the intake air amount detection means and the three oxygen concentration detection means or their calculated values with the normal values stored in advance. It is possible to accurately determine whether or not a failure has occurred.

It is a block diagram showing the whole engine composition concerning this embodiment. It is a conceptual diagram which shows typically the arrangement layout of sensors in an intake / exhaust system. It is a flowchart which shows the control content of the engine which concerns on this embodiment.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  An embodiment in which the present invention is applied to a diesel engine (hereinafter referred to as “engine” as appropriate) mounted on a vehicle will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the engine according to the present embodiment. In the engine 10 of the present embodiment shown in FIG. 1, a plurality of cylinder blocks 12 are provided, and a cylinder head 14 is provided on the top of each cylinder block 12. A fuel injection device 16 is provided at the center of each cylinder head 14, and an intake introduction portion and an exhaust discharge portion are provided on both sides of the fuel injection device 16 of the cylinder head 14. The intake air introduction portion is connected to the intake passage 18 via the intake manifold 17, and the exhaust discharge portion is connected to the exhaust passage 20 via the exhaust manifold 19.

  A supercharger 22 including a compressor provided in the intake passage 18 and an exhaust turbine provided in the exhaust passage 20 is disposed in the middle of the intake passage 18 and the exhaust passage 20. An exhaust gas purification device 24 equipped with a diesel particulate filter is provided in the exhaust passage 20 downstream of the supercharger 22.

  In order to promote fuel efficiency and exhaust gas purification action, a high pressure EGR passage 26 connecting the upstream exhaust passage 20 of the supercharger 22 and the downstream intake passage 18 of the supercharger 22, and the high pressure EGR passage 26 are connected to the high pressure EGR passage 26. And a high pressure EGR device 32 comprising a catalyst device 28 for purifying EGR gas and a high pressure EGR valve 30 provided at the outlet of the high pressure EGR passage 26 and capable of adjusting the flow rate of the EGR gas flowing through the high pressure EGR passage 26. Is provided. In addition, a low pressure EGR passage 34 connecting the downstream exhaust passage 20 of the supercharger 22 and the upstream intake passage 18 of the supercharger 22, a low pressure EGR cooler 36 interposed in the low pressure EGR passage 34, A low pressure EGR device 38 is provided which is provided at the outlet of the EGR passage 34 and includes a low pressure EGR valve 37 capable of adjusting the flow rate of the EGR gas flowing through the low pressure EGR passage 34.

  Here, with reference to FIG. 2 in addition to FIG. 1, the layout of the sensors in the intake / exhaust system will be described. FIG. 2 is a conceptual diagram schematically showing an arrangement layout of sensors in the intake / exhaust system.

  An intercooler 40 for cooling the intake air compressed and heated by the supercharger 22 is provided in the downstream intake passage 18 of the supercharger 22. An intake air amount sensor 41 (air flow sensor) for detecting an intake air amount to the intake passage 18 is located upstream of the low pressure EGR valve 37 in the intake passage 18 (upstream of the connection portion of the low pressure EGR passage 34 in the intake passage 18). ) Is provided. Further, on the downstream side of the high-pressure EGR valve 30 in the intake passage 18 (on the downstream side of the connection portion of the high-pressure EGR passage 26 in the intake passage 18), the first oxygen concentration for detecting the oxygen concentration of the intake air flowing through the intake passage 18 is detected. The oxygen concentration sensor 42 is provided. Further, the oxygen concentration in the intake passage 18 is downstream of the supercharger 22 in the intake passage 18 and upstream of the high-pressure EGR valve 30 (upstream of the connection portion of the high-pressure EGR passage 26 in the intake passage 18). A second oxygen concentration sensor 43 for detecting the above is provided. A third oxygen concentration sensor 44 for detecting the oxygen concentration in the exhaust passage 20 is provided on the downstream side of the supercharger 22 in the exhaust passage 20.

  It is noted that the third oxygen concentration sensor 44 is provided in the downstream side exhaust passage 20 of the supercharger 22 particularly upstream of the exhaust gas purification device 24 (more preferably, the catalyst included in the exhaust gas purification device 24). It is preferable because the oxygen concentration can be detected with higher accuracy.

Output signals from these sensors are transmitted to the ECU 50 which is a control unit that controls the engine 10, and control signals are transmitted to the low-pressure EGR device and the high-pressure EGR device based on the calculation results in the ECU 50, and various controls are performed. To be done. The ECU 50 includes a CPU (Central Processing Unit), a ROM (Read
This is an electronic control unit configured with only memory (RAM) and random access memory (RAM), and executes various controls according to a control program stored in a ROM. The electrical configuration is not limited to this.

  Next, the operation of the engine 10 in this embodiment will be briefly described. When the engine 10 starts operation, the exhaust turbine of the supercharger 22 is driven by the exhaust e. Then, the compressor of the supercharger 22 is rotationally driven in conjunction with the exhaust turbine, and the air is sucked into the intake passage 18. In addition, detection signals are input to the ECU 50 from each of the sensors while the engine 10 is in operation. The ECU 50 acquires these detection signals, and controls an intake throttle valve (not shown), the EGR valves 30, 36, the fuel injection device 16, the intercooler 40, and the like according to the calculation result.

In particular, when referring to an example of the control content of the low-pressure EGR device 38 and the high pressure EGR device 32, in the time of low load, recycled a large amount of exhaust in the high-pressure EGR device 32 to the intake passage 18, to reduce the exhaust amount of NO _X. During high load, it is recirculated to the intake passage 18 at a relatively high accuracy of a small amount of exhaust from the low-pressure EGR device 38, to reduce the exhaust amount of NO _X. Further, the intake air amount sensor 41 and the oxygen concentration sensors 42 to 44 detect the intake air amount and the oxygen concentration introduced into the cylinder, and input these detection signals to the ECU 50. The ECU 50 controls the supercharging pressure, the EGR gas amount introduced from the low pressure EGR device 38 and the high pressure EGR device 32, the fuel injection amount of the fuel injection device 16, and the injection timing in accordance with these detection signals. Thereby, it is possible to minimize the amount of NO _X in the exhaust gas.

  Next, with reference to FIG. 3, the control content of the engine 10 according to the present embodiment will be specifically described. FIG. 3 is a flowchart showing the control content of the engine 10 according to the present embodiment.

First, the ECU 50 starts the engine 10 and starts the high pressure EGR device 32 and the low pressure EGR device 38 to start supplying EGR gas (step S101). Subsequently, the detection value _CLAF2 is acquired from the second oxygen concentration sensor 43 (step S102), and the reference values C1 and C2 are acquired from storage means such as a memory built in the ECU 50 (step S103). Formula | C1-C _LAF2 | <C2 (1)
It is determined whether or not the condition is satisfied (step S104). Here, the reference value C1 is stored in advance as a detection value to be obtained from the second oxygen concentration sensor 43 when the high pressure EGR device 32 and the low pressure EGR device 38 are normal, and the reference value C2 is The absolute value of the difference between the actual measurement value of the second oxygen concentration sensor 43 and the normal value C1 is stored in advance as a threshold value for determining whether or not the low-pressure EGR device is normal. That is, in step S104, by determining whether or not the absolute value of the difference between the actual measurement value C _LAF2 of the second oxygen concentration sensor 43 and the normal value C1 is equal to or less than the allowable value C2, the low-pressure EGR device 38 is controlled. It is determined whether there is a failure.

If the above equation (1) is satisfied (step S104: YES), the ECU 50 determines that the low pressure EGR device 38 is normal (step S105). Subsequently, the ECU 50 obtains detection values m _a , C _LAFS1 , C _LAFS3 from the intake air amount sensor 41, the first oxygen concentration sensor 42, and the third oxygen concentration sensor 44, respectively (step S106), and these detection values. From the high pressure EGR ratio (the ratio of the EGR supply amount by the high pressure EGR device 32 out of the EGR supply amount of the entire system) R is calculated (step S107).

に、それぞれ各センサにおける検出値を代入し、連立して解くことにより、高圧ＥＧＲ量ｍ_ｅ−Ｈ、低圧ＥＧＲ量ｍ_ｅ−Ｌを算出する。そして、求めた高圧ＥＧＲ量ｍ_ｅ−Ｈ、低圧ＥＧＲ量ｍ_ｅ−Ｌを用いて、高圧ＥＧＲ割合Ｒを次式

により算出する。尚、上式（２）及び（３）の数値「０．２１１」は大気中の酸素濃度を表している。 Here, the calculation method of the high pressure EGR ratio R in step S107 will be described. First, the following equation relating each detected value m _a , C _LAFS1 , C _LAFS2 , C _LAFS3

The high pressure EGR amount me _-H and the low pressure EGR amount me _-L are calculated by substituting the detection values of the respective sensors and simultaneously solving them. Then, using the obtained high pressure EGR amount m _e-H and low pressure EGR amount m _e-L , the high pressure EGR ratio R is expressed by the following equation:

Calculated by The numerical value “0.211” in the above formulas (2) and (3) represents the oxygen concentration in the atmosphere.

Subsequently, the ECU 50 acquires reference values R1 and R2 from storage means such as a memory built in the ECU 50 (step S108), and the following expression | R1-R |> R2 (7)
It is determined whether or not the condition is satisfied (step S109). Here, the reference value R1 is stored in advance as a calculated value of the high-pressure EGR ratio that should be obtained when the high-pressure EGR device 32 and the low-pressure EGR device 38 are normal, and the reference value R2 is based on the actually measured value. The absolute value of the difference between the EGR ratio R calculated and the stored value R1 is stored in advance as a threshold value indicating an allowable range that the high-pressure EGR device 32 can consider to be normal. That is, in step S109, it is determined whether or not there is a failure in the high-pressure EGR device 32 by determining whether or not the absolute value of the difference between the calculated value R in step S107 and the normal value R1 is equal to or less than the allowable value R2. Determine.

  The ECU 50 starts timer counting when the above expression (7) is satisfied (step S110), and determines whether or not the determination result of step S109 continues for a predetermined period T1 or more (step S111). In other words, in step S111, the determination result continues for a predetermined period T1 or longer, so that a determination is made so that a transient erroneous determination is not performed, and the determination accuracy is improved. If the determination result in step S109 continues for a predetermined period T1 or longer (step S111: YES), the ECU 50 determines that the high-pressure EGR device 32 has a failure (step S112). The failure of the high pressure EGR device 32 determined in this way is warned by a notification means such as a warning sound or a display on the display (step S113).

  On the other hand, if the above equation (1) is not satisfied in step S104 (step S104: NO), the ECU 50 starts a timer count (step S114) and determines whether or not the determination result in step S104 continues for a predetermined period T2 or more. (Step S115). In other words, in step S115, the determination result continues for a predetermined period T2, thereby confirming that a transient erroneous determination is not performed and improving the determination accuracy. If the determination result in step S104 continues for a predetermined period T2 or longer, the ECU 50 determines that the low-pressure EGR device 38 has a failure (step S116).

Subsequently, the ECU 50 determines whether or not the detected value C _LAFS2 of the second oxygen concentration sensor 43 is equal to the atmospheric oxygen concentration acquired from the atmospheric oxygen concentration sensor not shown in FIG. 1 (step S117). Here, the determination in step S117 may be performed based on whether or not the difference between the reference atmospheric oxygen concentration and the detection value of the second oxygen concentration sensor 43 is within a predetermined value.

When the detection value _{CLAFS2 of} the second oxygen concentration sensor 43 is equal to the atmospheric oxygen concentration (step S117: YES), it indicates that the low pressure EGR valve 37 is firmly fixed and is not functioning ( (See FIG. 1). Therefore, the ECU 50 sets the low-pressure EGR amount (m _e−L ) to zero in the calculation (step S118), returns the process to step S106, and executes the processes after step S107, whereby the high-pressure EGR ratio R is calculated. Calculation is made to determine whether or not there is a failure in the high-pressure EGR device 32.

  In this case, the ECU 50 can determine that both the low pressure EGR device 38 and the high pressure EGR device 32 are out of order. When warning is performed in step S113, it is preferable to notify so that it is possible to determine which of the low-pressure EGR device 38 and the high-pressure EGR device 32 is normal and which is malfunctioning. In this embodiment, the failure determination result is only warned, but it goes without saying that other control may be executed using the determination result.

On the other hand, when the detection value _{CLAFS2 of} the second oxygen concentration sensor 43 is equal to the atmospheric oxygen concentration (step S117: NO), the process proceeds to step S113, and a warning is given that only the high-pressure EGR device has failed.

  As described above, according to the present invention, by comparing the measured values or the calculated values of the oxygen concentration sensors 42, 43, 44 arranged at three locations with the normal values stored in advance, the high-pressure EGR device or It is possible to accurately determine which of the low-pressure EGR devices has a failure.

In the above embodiment, it calculates the low-pressure EGR amount _{m e-L} and the high-pressure EGR amount _{m e-H,} a high-pressure EGR ratio R based on the low-pressure EGR amount _{m e-L} and the high-pressure EGR amount _{m e-H} The failure determination of the high-pressure EGR device 32 is performed by calculating and comparing with a normal high-pressure EGR ratio (normal value R1) stored in advance. For this reason, the abnormality of the high-pressure EGR device can be determined more accurately in the entire EGR system. Furthermore, by calculating the high pressure EGR ratio R, it is possible to easily determine the temperature change of the intake manifold due to the change in the low pressure EGR amount or the high pressure EGR amount me _-H without using a temperature sensor.

  In the above embodiment, the failure determination is performed by calculating the high-pressure EGR ratio. However, the failure determination of the high-pressure EGR device 32 is performed by comparing the calculation result of the high-pressure EGR amount with the normal high-pressure EGR amount stored in advance. May be performed. In that case, the calculation load of the ECU 50 can be reduced.

  The present invention is applicable to an exhaust gas recirculation device capable of detecting a failure such as sticking of an EGR valve for adjusting the exhaust gas recirculation amount.

DESCRIPTION OF SYMBOLS 10 Engine 12 Cylinder block 14 Cylinder head 16 Fuel injection device 17 Intake manifold 18 Intake passage 19 Exhaust manifold 20 Exhaust passage 22 Supercharger 24 Exhaust gas purification device 26 High pressure EGR passage 28 Catalytic device 30 High pressure EGR valve 32 High pressure EGR device 34 Low pressure EGR Passage 36 Low pressure EGR cooler 37 Low pressure EGR valve 38 Low pressure EGR device 40 Intercooler 41 Intake amount sensor 42 First oxygen concentration sensor 43 Second oxygen concentration sensor 44 Third oxygen concentration sensor

Claims (4)

An exhaust turbine provided in the exhaust passage of the engine and driven to rotate by exhaust gas flowing through the exhaust passage; and an intake turbine provided in the intake passage of the engine and driven to rotate in conjunction with the exhaust turbine. A supercharger having a compressor for compressing and supplying
A high-pressure EGR passage for introducing exhaust gas from the upstream side of the exhaust passage to the downstream side of the compressor of the intake passage, and a high-pressure EGR for adjusting the amount of exhaust gas passing through the high-pressure EGR passage High pressure EGR means having flow rate control means;
A low-pressure EGR passage for introducing exhaust gas from a downstream side of the exhaust passage to the upstream side of the compressor in the intake passage, and a low-pressure EGR for adjusting the amount of exhaust gas passing through the low-pressure EGR passage Low pressure EGR means comprising flow rate control means;
An exhaust gas recirculation apparatus comprising: an EGR amount control means for adjusting an amount of exhaust gas recirculated to the intake passage by controlling the high pressure EGR flow rate control means and the low pressure EGR flow rate control means;
An intake air amount detecting means for detecting an intake air amount upstream of the connecting portion of the low pressure EGR passage in the intake passage;
A first oxygen concentration detection means for detecting an oxygen concentration downstream of the connecting portion of the high pressure EGR passage in the intake passage;
A second oxygen concentration detection means for detecting an oxygen concentration downstream of the compressor in the intake passage and upstream of a connecting portion of the high pressure EGR passage;
A third oxygen concentration detection means for detecting an oxygen concentration downstream of the exhaust turbine in the exhaust passage;
An actual measurement value is acquired by the second oxygen concentration detection means, and the failure determination of the low pressure EGR means is performed by comparing the actual measurement value with a reference value, and the intake air amount detection means and the first to third oxygen oxygen detection means A failure determination unit that acquires an actual measurement value by the concentration detection unit and performs a failure determination of the high pressure EGR unit based on the low pressure EGR amount and the high pressure EGR amount calculated from the actual measurement value ;
The exhaust gas recirculation apparatus according to claim 1, wherein the failure determination means determines a failure of the high pressure EGR means when it is determined that the low pressure EGR means is not broken .   The failure determination means calculates a low pressure EGR amount based on the actual measurement values of the intake air amount detection means and the second and third oxygen concentration detection means, and the intake air amount detection means and the first to third oxygen concentrations. A high pressure EGR amount is calculated based on an actual measurement value of the concentration detection means, a high pressure EGR ratio is calculated based on the low pressure EGR amount and the high pressure EGR amount, and compared with a normal high pressure EGR ratio stored in advance. The exhaust gas recirculation apparatus according to claim 1, wherein a failure determination of the high-pressure EGR means is performed.   The failure determination means determines that the low-pressure EGR means has zero return when the low-pressure EGR means is determined to be failed and the detection value of the second oxygen concentration detection means is equal to the atmospheric oxygen concentration. The exhaust gas recirculation apparatus according to claim 1 or 2, wherein the high-pressure EGR ratio is calculated as follows. 4. The failure determination unit according to claim 1, wherein the failure determination unit performs the failure determination when exhaust gas is supplied to the intake passage from the low pressure EGR unit and the high pressure EGR unit. The exhaust gas recirculation device described.

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