JP2008038648A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for suitably controlling gas composition and intake gas quantity by accurately calculating both of low pressure EGR gas quantity and high pressure EGR gas quantity in an exhaust gas recirculation device for an internal combustion engine. <P>SOLUTION: Compressor passing gas quantity is acquired from fore-and-aft pressures of a compressor and rotation speed of the compressor (S103). Low pressure EGR gas quantity is calculated from compressor passing gas quantity and fresh air quantity (S104), and high pressure EGR gas quantity is calculated from compressor passing gas quantity and suction air quantity (S105). Low pressure EGR gas quantity and high pressure EGR gas quantity are controlled to target quantities, respectively (S106). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

A so-called high pressure exhaust gas recirculation (hereinafter referred to as EGR) passage that connects the intake passage and the exhaust passage downstream of the throttle valve is provided. A technique for accurately estimating the engine load obtained from the number or the like is known (for example, see Patent Document 1).
JP 2004-197616 A JP 2006-9745 A Japanese Patent No. 3608463 JP 2005-127261 A

  By the way, in addition to the high pressure EGR passage disclosed in Patent Document 1, a part of the exhaust gas is taken in as low pressure EGR gas from the exhaust passage downstream of the turbine, and the low pressure EGR gas is recirculated to the intake passage upstream of the compressor. An EGR passage may be provided.

  In such an apparatus using both the high pressure EGR passage and the low pressure EGR passage, the amount and composition of the intake air flowing into the internal combustion engine cannot be controlled unless both the low pressure EGR gas amount and the high pressure EGR gas amount are accurately estimated. The combustion of an internal combustion engine may not be stable.

  The present invention has been made in view of the above circumstances, and an object thereof is to accurately calculate both the low-pressure EGR gas amount and the high-pressure EGR gas amount in an exhaust gas recirculation device for an internal combustion engine, The object is to provide a technique for suitably controlling the gas composition.

In the present invention, the following configuration is adopted. That is,
A turbocharger having a turbine disposed in an exhaust passage of the internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
Compressor front-rear pressure calculating means for calculating the front-rear pressure of the compressor;
Compressor speed detecting means for detecting the speed of the compressor;
A compressor passage gas amount acquisition means for acquiring a compressor passage gas amount from the compressor front and rear pressure calculated by the compressor front and rear pressure calculation means and the compressor rotation speed detected by the compressor rotation speed detection means;
Fresh air amount measuring means for measuring the fresh air amount in the intake passage upstream of the connection portion of the low pressure EGR passage;
An intake air amount calculating means for calculating an intake air amount taken into the internal combustion engine;
Low pressure EGR gas amount calculating means for calculating the low pressure EGR gas amount from the compressor passing gas amount acquired by the compressor passing gas amount acquiring means and the fresh air amount measured by the new air amount measuring means;
High pressure EGR gas amount calculating means for calculating the high pressure EGR gas amount from the compressor passing gas amount acquired by the compressor passing gas amount acquiring means and the intake air amount calculated by the intake air amount calculating means;
EGR gas amount control means for controlling the low pressure EGR gas amount calculated by the low pressure EGR gas amount calculation means and the high pressure EGR gas amount calculation means by the high pressure EGR gas amount calculation means to respective target amounts;
An exhaust gas recirculation device for an internal combustion engine.

  Here, in the apparatus using both the high pressure EGR passage and the low pressure EGR passage, the amount and composition of the intake air flowing into the internal combustion engine cannot be controlled unless both the low pressure EGR gas amount and the high pressure EGR gas amount are accurately estimated. The combustion of an internal combustion engine may not be stable.

  Therefore, in the present invention, the amount of gas passing through the compressor is obtained from the pressure before and after the compressor and the rotation speed of the compressor, the amount of low-pressure EGR gas is calculated from the amount of gas passing through the compressor and the amount of fresh air, and the amount of gas passing through the compressor and the amount of intake air. From this, the amount of high-pressure EGR gas is calculated.

  According to this, both the low pressure EGR gas amount and the high pressure EGR gas amount can be accurately calculated, and the intake gas amount and gas are controlled by controlling the low pressure EGR gas amount and the high pressure EGR gas amount to the respective target amounts. The composition can be suitably controlled.

  Compressor passing gas amount correcting means for correcting the compressor passing gas amount acquired by the compressor passing gas amount acquiring means based on the fresh air amount measured by the fresh air amount measuring means when the low pressure EGR gas amount is 0; It is good to have.

  When the low-pressure EGR gas amount is 0, the new air amount and the compressor passing gas amount theoretically coincide. Therefore, if the fresh air amount and the compressor passing gas amount at this time are different, if the fresh air amount measured by the fresh air measuring means is a true value, the acquired compressor passing gas amount Is deviated from the true value. Using this relationship, the amount of fresh gas is corrected to correct the amount of gas passing through the compressor. Thereby, the compressor passage gas amount is corrected to a true value, and both the low pressure EGR gas amount and the high pressure EGR gas amount can be accurately calculated.

  If the difference between the compressor passing gas amount acquired by the compressor passing gas amount acquiring means when the low pressure EGR gas amount is 0 and the fresh air amount measured by the new air amount measuring means is greater than a certain value, the fresh air It is preferable to provide an abnormality determining means for determining that the amount measuring means is abnormal.

  When the low-pressure EGR gas amount is 0, the new air amount and the compressor passing gas amount theoretically coincide. For this reason, when the values of the fresh air amount and the compressor passing gas amount are more than a certain value, if the compressor passing gas amount is a value close to the true value although there is some error, the fresh air amount is reduced. It is considered that an abnormality occurs in the fresh air amount measuring means to be measured and the fresh air amount becomes an abnormal value. Using this relationship, if the difference between the amount of gas passing through the compressor and the amount of fresh air deviates by a certain value or more, it is determined that the fresh air amount measuring means is faulty and the fresh air amount measuring means is abnormal. Thereby, abnormality of a new air quantity measuring means can be discovered.

  According to the present invention, in the exhaust gas recirculation device for an internal combustion engine, both the low-pressure EGR gas amount and the high-pressure EGR gas amount can be accurately calculated, and the intake gas amount and gas composition can be suitably controlled.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied and its intake / exhaust system. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.

  An intake passage 3 and an exhaust passage 4 are connected to the internal combustion engine 1. In the middle of the intake passage 3 connected to the internal combustion engine 1, a compressor housing 5a of a turbocharger 5 that operates using exhaust energy as a drive source is disposed.

  An air flow meter 6 that outputs a signal corresponding to the flow rate of fresh intake air (hereinafter referred to as fresh air) flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the compressor housing 5a. Yes. The air flow meter 6 measures the amount of fresh air in the internal combustion engine 1. The air flow meter 6 corresponds to the new air volume measuring means of the present invention.

  On the other hand, an atmospheric pressure sensor 7 for detecting atmospheric pressure is disposed near the inlet of the intake passage 3 that takes in the intake air from the atmosphere upstream of the air flow meter 6 into the intake passage 3.

  An intake pressure sensor 8 that detects the intake pressure of the intake passage 3 downstream of the compressor housing 5a is disposed in the intake passage 3 downstream of the compressor housing 5a. Similarly, an intake air temperature sensor 9 for detecting the intake air temperature of the intake air passage 3 downstream of the compressor housing 5a is disposed in the intake air passage 3 downstream of the compressor housing 5a.

  Here, a compressor rotation speed sensor 10 for detecting the rotation speed of the compressor is disposed in the compressor housing 5a. The compressor rotation speed sensor 10 corresponds to the compressor rotation speed detection means of the present invention.

  On the other hand, a turbine housing 5 b of the turbocharger 5 is arranged in the middle of the exhaust passage 4 connected to the internal combustion engine 1. A particulate filter (hereinafter referred to as a filter) 11 is disposed in the exhaust passage 4 downstream of the turbine housing 5b. The filter 11 carries an NOx storage reduction catalyst (hereinafter referred to as NOx catalyst). The filter 11 collects particulate matter in the exhaust gas. Further, the NOx catalyst occludes nitrogen oxide (NOx) in the exhaust gas when the oxygen concentration of the exhaust gas flowing into the NOx catalyst is high, and on the other hand, when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. Releases the stored NOx. At that time, if a reducing component such as hydrocarbon (HC) or carbon monoxide (CO) is present in the exhaust, NOx released from the NOx catalyst is reduced. Note that an oxidation catalyst or a three-way catalyst may be supported on the filter 11 instead of the NOx catalyst.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31 and a low pressure EGR valve 32.

  The low pressure EGR passage 31 connects the exhaust passage 4 downstream of the filter 11 and the intake passage 3 upstream of the compressor housing 5 a and downstream of the air flow meter 6. Exhaust gas is recirculated to the internal combustion engine 1 at a low pressure through the low pressure EGR passage 31. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas.

  Further, the low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31.

  The internal combustion engine 1 is provided with a high-pressure EGR device 40 that recirculates a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a high pressure. The high pressure EGR device 40 includes a high pressure EGR passage 41 and a high pressure EGR valve 42.

  The high pressure EGR passage 41 connects the exhaust passage 4 upstream of the turbine housing 5b and the intake passage 3 downstream of the compressor housing 5a. Exhaust gas is recirculated to the internal combustion engine 1 at a high pressure through the high pressure EGR passage 41. In this embodiment, the exhaust gas recirculated through the high pressure EGR passage 41 is referred to as high pressure EGR gas.

  Further, the high pressure EGR valve 42 adjusts the amount of high pressure EGR gas flowing through the high pressure EGR passage 41 by adjusting the passage sectional area of the high pressure EGR passage 41.

  The internal combustion engine 1 configured as described above is provided with an ECU 12 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 12 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition, the ECU 12 receives an air flow meter 6, an atmospheric pressure sensor 7, an intake pressure sensor 8, an intake air temperature sensor 9, a compressor rotation speed sensor 10, and an electric signal corresponding to the amount by which the driver depresses the accelerator pedal 13. An accelerator opening sensor 14 that can output and detect the engine load and a crank position sensor 15 that detects the engine rotation speed are connected via electric wiring, and output signals of these various sensors are input to the ECU 12. Yes.

  On the other hand, a low-pressure EGR valve 32 and a high-pressure EGR valve 42 are connected to the ECU 12 via electric wiring, and these devices are controlled by the ECU 12. Then, by controlling the low pressure EGR valve 32 and the high pressure EGR valve 42, the low pressure EGR gas amount and the high pressure EGR gas amount contained in the intake air sucked into the internal combustion engine 1 are adjusted.

  Here, in the exhaust gas recirculation device that uses both the low pressure EGR passage 31 and the high pressure EGR passage 41, if both the low pressure EGR gas amount and the high pressure EGR gas amount are not accurately estimated, the amount and gas of the intake air flowing into the internal combustion engine 1 will be described. The composition cannot be controlled, and the combustion of the internal combustion engine 1 may not be stable.

  Therefore, in the present embodiment, the low pressure EGR gas amount and the high pressure EGR gas amount are accurately calculated, and the intake air flowing into the internal combustion engine 1 is controlled by controlling the low pressure EGR gas amount and the high pressure EGR gas amount to the respective target amounts. The gas composition of the intake air composed of the amount of gas, the amount of fresh air, the amount of low-pressure EGR gas, and the amount of high-pressure EGR gas is controlled. Thus, in this embodiment, the combustion of the internal combustion engine 1 can be stabilized.

  Here, the sum of the fresh air amount measured by the air flow meter 6 and the low pressure EGR gas amount is the compressor passing gas amount. From this, the low pressure EGR gas amount is calculated by subtracting the fresh air amount from the compressor passing gas amount (low pressure EGR gas amount = compressor passing gas amount−fresh air amount). Thereby, an accurate low-pressure EGR gas amount can be calculated.

  Further, the sum of the compressor passing gas amount and the high pressure EGR gas amount is the intake air amount finally sucked into the internal combustion engine 1. Therefore, the high pressure EGR gas amount is calculated by subtracting the compressor passage gas amount from the intake amount (high pressure EGR gas amount = intake amount−compressor passage gas amount). Thereby, an accurate high-pressure EGR gas amount can be calculated.

The compressor passage gas amount is calculated by subtracting the atmospheric pressure detected by the atmospheric pressure sensor 7 from the intake pressure of the intake passage 3 downstream of the compressor housing 5a detected by the intake pressure sensor 8 (= (Intake air pressure−atmospheric pressure) and the compressor rotation speed detected by the compressor rotation speed sensor 10 are acquired by applying them to a map.

  The intake air amount includes the intake pressure in the intake passage 3 downstream of the compressor housing 5a detected by the intake pressure sensor 8, the intake air temperature in the intake passage 3 downstream of the compressor housing 5a detected by the intake air temperature sensor 9, and the crank It is calculated from the engine speed detected by the position sensor 15.

  Here, the target amounts of the low-pressure EGR gas amount and the high-pressure EGR gas amount are values that are appropriately set according to the operating state of the internal combustion engine 1 and the environmental conditions.

  Next, the flow of EGR gas amount control according to this embodiment will be described. FIG. 2 is a flowchart showing a flow of EGR gas amount control according to this embodiment. This routine is repeatedly executed every predetermined time.

  In step S101, the ECU 12 determines whether or not the low pressure EGR gas and the high pressure EGR gas are circulated. Whether the low-pressure EGR gas and the high-pressure EGR gas are circulated is determined by detecting the opening degree of the low-pressure EGR valve 32 and the opening degree of the high-pressure EGR valve 42 by an opening sensor (not shown) and opening / closing states thereof. The

  If it is determined in step S101 that the low pressure EGR valve 32 and / or the high pressure EGR valve 42 are in the closed state and the low pressure EGR gas and the high pressure EGR gas are not circulated, the ECU 12 once ends this routine. To do. When it is determined that the low pressure EGR valve 32 and the high pressure EGR valve 42 are in the open state and the low pressure EGR gas and the high pressure EGR gas are circulated, the process proceeds to step S102.

  In step S102, the ECU 11 processes input signals from the air flow meter 6, the atmospheric pressure sensor 7, the intake pressure sensor 8, the intake air temperature sensor 9, the compressor rotation speed sensor 10, the accelerator opening sensor 14, the crank position sensor 15, and the like. To do.

  In step S103 subsequent to step S102, the ECU 11 acquires the compressor passing gas amount. The amount of gas passing through the compressor is calculated by subtracting the atmospheric pressure detected by the atmospheric pressure sensor 7 from the intake pressure of the intake passage 3 downstream of the compressor housing 5a detected by the intake pressure sensor 8, and the compressor rotation It can be obtained by applying the compressor rotation speed detected by the number sensor 10 to the map. A map representing the correlation among the amount of gas passing through the compressor, the pressure before and after the compressor, and the number of rotations of the compressor is obtained in advance through experiments and stored in the ECU 12.

  Here, the ECU 12 that calculates the compressor longitudinal pressure by subtracting the atmospheric pressure detected by the atmospheric pressure sensor 7 from the intake pressure detected by the intake pressure sensor 8 in this step corresponds to the compressor longitudinal pressure calculating means of the present invention. Moreover, ECU12 which acquires the compressor passage gas amount in this step corresponds to the compressor passage gas amount acquisition means of the present invention.

  In step S104 subsequent to step S103, the ECU 12 calculates a low pressure EGR gas amount. The low-pressure EGR gas amount is calculated by subtracting the fresh air amount measured by the air flow meter 6 from the compressor passing gas amount acquired in step S103.

  Here, the ECU 12 that calculates the low pressure EGR gas amount in this step corresponds to the low pressure EGR gas amount calculation means of the present invention.

  In step S105 subsequent to step S104, the ECU 12 calculates the high-pressure EGR gas amount. The high-pressure EGR gas amount is calculated by subtracting the compressor passage gas amount acquired in step S103 from the intake amount finally sucked into the internal combustion engine 1.

  Here, the ECU 12 that calculates the high-pressure EGR gas amount in this step corresponds to the high-pressure EGR gas amount calculation means of the present invention.

  In this step, the intake air amount is determined by the intake pressure in the intake passage 3 downstream of the compressor housing 5 a detected by the intake pressure sensor 8 and the intake air temperature in the intake passage 3 downstream of the compressor housing 5 a detected by the intake temperature sensor 9. , And the engine speed detected by the crank position sensor 15. The ECU 12 for calculating the intake air amount in this step corresponds to the intake air amount calculating means of the present invention.

  In step S106 subsequent to step S105, the ECU 12 controls the opening degree of the low pressure EGR valve 32 and the high pressure EGR so as to control the low pressure EGR gas amount calculated in step S104 and the high pressure EGR gas amount calculated in step S105 to the respective target amounts. The opening degree of the valve 42 is adjusted.

  That is, the opening degree of the low pressure EGR valve 32 is adjusted according to the difference between the low pressure EGR gas amount and the target amount thereof, and the high pressure EGR valve 42 is opened according to the difference between the high pressure EGR gas amount and the target amount thereof. Adjust the degree.

  Here, the adjustment opening amounts of the low pressure EGR valve 32 and the high pressure EGR valve 42 can be obtained by applying the difference between the low pressure EGR gas amount and the high pressure EGR gas amount and their target amounts to a map. A map representing the correlation between the opening amount and the difference is obtained in advance by experiments or the like and stored in the ECU 12.

  In this step, the ECU 12 that controls the low pressure EGR gas amount and the high pressure EGR gas amount to the respective target amounts by adjusting the opening of the low pressure EGR valve 32 and the high pressure EGR valve 42 is used as the EGR gas amount control means of the present invention. Equivalent to.

  According to the EGR gas amount control explained above, the low pressure EGR gas amount and the high pressure EGR gas amount are accurately calculated, and the low pressure EGR gas amount and the high pressure EGR gas amount are controlled to the respective target amounts, whereby the internal combustion engine 1 is controlled. The amount of inflowing intake gas and the intake gas composition can be controlled, and combustion of the internal combustion engine 1 can be stabilized.

  Incidentally, the characteristics of the compressor in the compressor housing 5a may change over time due to deposits (deposits).

  Therefore, in this embodiment, the compressor passage gas acquired in step S103 in the EGR gas amount control flow shown in FIG. 2 based on the fresh air amount measured by the air flow meter 6 when the low pressure EGR gas amount is zero. The amount is corrected.

  When the low-pressure EGR gas amount is 0, the new air amount and the compressor passing gas amount theoretically coincide. Therefore, if the fresh air amount and the compressor passing gas amount at this time are different, the compressor passing gas amount deviates from the true value if the fresh air amount measured by the air flow meter 6 is a true value. Will be. Using this relationship, the amount of fresh gas is corrected to correct the amount of gas passing through the compressor.

Specifically, a correction coefficient is calculated from the fresh air amount and the compressor passing gas amount when the low pressure EGR gas amount is 0, and the correction coefficient is acquired in step S103 in the next EGR gas amount control flow of FIG. Accumulate and reflect the amount of gas passing through the compressor.

  Next, the flow of compressor passing gas amount correction control according to this embodiment will be described. FIG. 3 is a flowchart showing a flow of compressor passage gas amount correction control according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 12 that executes this routine corresponds to the compressor passing gas amount correcting means of the present invention.

  In step S201, the ECU 12 determines whether or not a compressor passing gas amount correction condition is satisfied. Whether or not the compressor passage gas amount correction condition is satisfied is determined by whether or not the vehicle travel distance has passed a certain distance from the previous execution of correction of the compressor passage gas amount. Note that the vehicle travel distance of a certain distance from the previous correction execution is a distance that causes a change in the characteristics of the compressor over time and requires further correction to the compressor passage gas amount.

  In step S201, when it is determined that the vehicle travel distance has not passed the fixed distance from the previous correction execution and does not satisfy the compressor passage gas amount correction condition, the ECU 12 once ends this routine. If it is determined that the vehicle travel distance has passed a certain distance from the previous correction execution and the compressor passing gas amount correction condition is satisfied, the process proceeds to step S202.

  In step S202, the ECU 12 determines whether or not the low pressure EGR gas amount is zero. Whether or not the low-pressure EGR gas amount is 0 is determined by detecting the opening degree of the low-pressure EGR valve 32 with an opening degree sensor (not shown) and determining whether or not the valve is closed.

  If it is determined in step S202 that the low pressure EGR valve 32 is in the open state and the low pressure EGR gas amount is not zero, the ECU 12 once ends this routine. When it is determined that the low pressure EGR valve 32 is in the closed state and the low pressure EGR gas amount is 0, the process proceeds to step S203.

  This step may be a step of forcibly closing the low pressure EGR valve 32 by controlling the opening of the low pressure EGR valve 32 so that the low pressure EGR gas amount becomes zero.

  In step S203, the ECU 12 determines whether or not the air flow meter 6 is in an energized state. Whether or not the air flow meter 6 is energized is determined by whether or not a signal is input from the air flow meter 6 to the ECU 12.

  When it is determined in step S203 that the air flow meter 6 is not energized, the ECU 12 once ends this routine. If it is determined that the air flow meter 6 is in the energized state, the process proceeds to step S204.

  In step S204, the ECU 12 determines whether or not the fluctuation range of the fresh air amount detected by the air flow meter 6 is equal to or less than a certain value.

  This is because there is a gas delay element due to an air cleaner or piping in the intake passage 3 from the air flow meter 6 to the compressor housing 5a, and the adverse effect on the correction due to the delay is avoided, and the gas amount is corrected in a stable state. It is for implementing. Note that the fluctuation range of the fresh air amount below a certain value is a state in which the fresh air amount is stable and an adverse effect on correction due to gas delay can be avoided.

In step S204, when it is determined that the fluctuation range of the fresh air amount is not equal to or less than the predetermined value, the ECU 12 once ends this routine. If it is determined that the fluctuation range of the fresh air amount is equal to or less than a certain value, the process proceeds to step S205.

  In step S205, the ECU 12 calculates a correction coefficient for the compressor passage gas amount. The correction coefficient is a ratio value (correction coefficient) between the fresh air amount measured by the air flow meter 6 when the low pressure EGR gas amount is 0 and the compressor passing gas amount acquired in step S103 in the EGR gas amount control flow of FIG. = New air volume / compressor gas volume).

  In step S206 subsequent to step S205, the ECU 12 integrates and reflects the correction coefficient calculated in step S205 in the compressor passage gas amount acquired in step S103 in the next EGR gas amount control flow of FIG. 2 (after correction). Compressor passing gas amount = compressor passing gas amount in step S103 × correction coefficient). This correction coefficient continues to be reflected until the correction coefficient is calculated again by the next execution of this flow.

  According to the compressor passing gas amount correction control described above, the compressor passing gas amount acquired in step S103 is corrected to a true value in the EGR gas amount control flow of FIG. 2, and both the low pressure EGR gas amount and the high pressure EGR gas amount are adjusted. It can be calculated accurately.

  By the way, the air flow meter 6 may break down and output abnormally. In this case, if the air flow meter 6 is not determined to be abnormal, various controls such as the EGR gas amount control flow of FIG. 2 and the compressor passage gas amount correction control flow of FIG. Could be done.

  Therefore, in this embodiment, the compressor passage gas amount acquired in step S103 in the EGR gas amount control flow shown in FIG. 2 when the low pressure EGR gas amount is 0 and the new air amount measured by the air flow meter 6 are as follows. If the difference is a certain value or more, it is determined that the air flow meter 6 is abnormal.

  When the low-pressure EGR gas amount is 0, the new air amount and the compressor passing gas amount theoretically coincide. For this reason, if the value of the fresh air amount and the amount of gas passing through the compressor at this time are apart from each other by a certain value or more, if the amount of gas passing through the compressor is somewhat close to the true value although there is some error, the new amount It is considered that an abnormality occurs in the air flow meter 6 that measures the air volume, and the new air volume is an abnormal value. Using this relationship, if the difference between the amount of gas passing through the compressor and the amount of fresh air deviates by a certain value or more, it is determined that the air flow meter 6 is abnormal due to a failure or the like in the air flow meter 6.

  Next, an abnormality determination control flow of the air flow meter 6 according to the present embodiment will be described. FIG. 4 is a flowchart showing a flow of abnormality determination control of the air flow meter 6 according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 12 that executes this routine corresponds to the abnormality determination means of the present invention.

  In step S301, the ECU 12 determines whether or not the correction of the compressor passage gas amount has been completed. Whether or not the correction of the compressor passage gas amount has been completed is determined by whether or not the ECU 12 is executing the compressor passage gas amount correction control flow of FIG.

  In step S301, when it is determined that the correction of the compressor passage gas amount is not completed, the ECU 12 once ends this routine. If it is determined that the correction of the compressor passage gas amount has been completed, the process proceeds to step S302.

  In step S302, the ECU 12 determines whether or not the vehicle travel distance is within a certain distance from the previous execution of the compressor passage gas amount correction. Note that the vehicle travel distance of a certain distance from the previous correction execution is a value that is close to the true value, although the aging of the compressor characteristics has not progressed much and the corrected compressor passage gas amount has some errors. It is a distance that can be determined.

  If it is determined in step S302 that the vehicle travel distance is not within a certain distance from the previous correction execution, the ECU 12 once ends this routine. If the vehicle travel distance is within a certain distance from the previous correction execution, the process proceeds to step S303.

  In step S303, the ECU 12 determines whether or not the low pressure EGR gas amount is zero. This step is the same as S202.

  In step S304, the ECU 12 determines whether or not the air flow meter 6 is in an energized state. This step is the same as S203.

  In step S305, the ECU 12 determines whether or not the fluctuation range of the fresh air amount detected by the air flow meter 6 is equal to or less than a certain value. This step is the same as S204.

  In step S306, the ECU 12 calculates a difference (= | ΔV |) between the compressor passing gas amount and the fresh air amount, and determines whether or not the difference becomes a certain value or more (| ΔV | ≧ constant value). . The difference is the absolute value of the difference between the fresh air amount measured by the air flow meter 6 when the low pressure EGR gas amount is 0 and the compressor passing gas amount acquired in step S103 in the EGR gas amount control flow of FIG. .

  When an affirmative determination is made in step S306 (when | ΔV | ≧ a constant value), the ECU 12 determines that the air flow meter 6 is abnormal in step S307.

  On the other hand, if a negative determination is made in step S306 (when | ΔV | <a constant value), the air flow meter 6 is operating normally, and the ECU 12 once ends this routine.

  According to the abnormality determination control of the air flow meter 6 described above, the abnormality of the air flow meter 6 used for various controls can be found, and various controls are executed without the air flow meter 6 being determined as abnormal. It is possible to prevent the control from being performed.

  In this embodiment, the control of the low pressure EGR gas amount and the high pressure EGR gas amount is performed only by adjusting the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42. However, the present invention is not limited to this, and by adjusting the opening of the throttle (not shown) and the opening of the exhaust throttle valve, the opening of the low-pressure EGR valve 32 and the opening of the high-pressure EGR valve 42 are adjusted, and the low-pressure EGR gas amount is adjusted. In addition, the amount of high pressure EGR gas may be controlled.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. 3 is a flowchart showing a flow of EGR gas amount control according to the first embodiment. 4 is a flowchart illustrating a flow of compressor passage gas amount correction control according to the first embodiment. 3 is a flowchart illustrating a flow of abnormality determination control of the air flow meter according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor housing 5b Turbine housing 6 Air flow meter 7 Atmospheric pressure sensor 8 Intake pressure sensor 9 Intake temperature sensor 10 Compressor rotation speed sensor 11 Filter 13 Accelerator pedal 14 Accelerator opening sensor 15 Crank position sensor 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 40 High pressure EGR device 41 High pressure EGR passage 42 High pressure EGR valve

Claims (3)

A turbocharger having a turbine disposed in an exhaust passage of the internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
Compressor front-rear pressure calculating means for calculating the front-rear pressure of the compressor;
Compressor speed detecting means for detecting the speed of the compressor;
A compressor passage gas amount acquisition means for acquiring a compressor passage gas amount from the compressor front and rear pressure calculated by the compressor front and rear pressure calculation means and the compressor rotation speed detected by the compressor rotation speed detection means;
Fresh air amount measuring means for measuring the fresh air amount in the intake passage upstream of the connection portion of the low pressure EGR passage;
An intake air amount calculating means for calculating an intake air amount taken into the internal combustion engine;
Low pressure EGR gas amount calculating means for calculating the low pressure EGR gas amount from the compressor passing gas amount acquired by the compressor passing gas amount acquiring means and the fresh air amount measured by the new air amount measuring means;
High pressure EGR gas amount calculating means for calculating the high pressure EGR gas amount from the compressor passing gas amount acquired by the compressor passing gas amount acquiring means and the intake air amount calculated by the intake air amount calculating means;
EGR gas amount control means for controlling the low pressure EGR gas amount calculated by the low pressure EGR gas amount calculation means and the high pressure EGR gas amount calculation means by the high pressure EGR gas amount calculation means to respective target amounts;
An exhaust gas recirculation device for an internal combustion engine.   Compressor passing gas amount correcting means for correcting the compressor passing gas amount acquired by the compressor passing gas amount acquiring means based on the fresh air amount measured by the fresh air amount measuring means when the low pressure EGR gas amount is 0; The exhaust gas recirculation device for an internal combustion engine according to claim 1, further comprising: If the difference between the compressor passing gas amount acquired by the compressor passing gas amount acquiring means when the low pressure EGR gas amount is 0 and the fresh air amount measured by the new air amount measuring means is greater than a certain value, the fresh air 2. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, further comprising abnormality determining means for determining that the amount measuring means is abnormal.

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