JP2013083249A - Egr system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an EGR device with sufficient accuracy and also reduce cost by predicting opening of a valve of the EGR device without using a lift sensor.SOLUTION: In an EGR system 10, in an inactive condition of an EGR device 20, by using the sensors 100-108, 130-134, the air intake state and intake air volume of an intake system 14, negative pressure of the air intake and/or engine revolution are detected, respectively. Based on the detected air intake state and the intake air volume, the negative pressure of the air intake and/or the engine revolution, an ECU110 predicts the opening of a valve 24 of the EGR device 20 using maps 138, 140, 144.

Description

  According to the present invention, an exhaust gas recirculation device (hereinafter also referred to as an EGR device) is provided in an exhaust gas recirculation means that connects an intake system and an exhaust system of an internal combustion engine. The present invention relates to an EGR system that recirculates a part from an exhaust system to an intake system.

  Conventionally, an EGR system including an EGR device has been used to remove harmful components in exhaust gas discharged from an internal combustion engine. In the EGR system, an EGR device is provided in the middle of the exhaust gas recirculation means for connecting the intake system and the exhaust system of the internal combustion engine, and the exhaust system is exhausted by communicating the intake system and the exhaust system by the EGR device. A part of the exhaust gas is recirculated to the intake system to reduce harmful components such as NOx contained in the exhaust gas.

  By the way, Patent Documents 1 and 2 disclose techniques for diagnosing the presence or absence of a failure in an EGR system including an EGR device.

  In Patent Document 1, in the EGR device, the position (lift amount, opening degree) of a valve for controlling the flow rate of exhaust gas is detected by a lift sensor (opening degree sensor), and EGR is determined based on the detected lift amount of the valve. It is disclosed to diagnose the presence or absence of a failure in an EGR system including a device.

  Patent Document 2 discloses that a negative pressure of intake air sucked into an internal combustion engine from an intake manifold (intake system) is measured, and an abnormality of the EGR device is detected based on the measured negative pressure.

Japanese Examined Patent Publication No. 2-46787 JP 2009-287392 A

  In the above-mentioned EGR system, if there is adhesion of combustion products due to combustion of the internal combustion engine on the valve or exhaust gas recirculation means of the EGR device, the recirculation amount of exhaust gas recirculated from the exhaust system to the intake system decreases. To do. As a result, even if the EGR device is controlled to recirculate the exhaust gas having a desired recirculation amount to the intake system, the desired recirculation amount and the actual recirculation amount are different.

  Therefore, even if the recirculation amount of the exhaust gas is controlled based on the lift amount of the valve detected by the lift sensor using the technique of Patent Document 1, the recirculation amount of the exhaust gas can be appropriately controlled or the EGR device It becomes difficult to detect a failure.

  Further, since the lift sensor is relatively expensive, the cost for detecting the position of the valve of the EGR device and diagnosing whether or not the EGR device is faulty increases.

  On the other hand, the technique of Patent Document 2 diagnoses the presence or absence of a failure of the EGR device based only on the negative pressure of the intake air. Since the negative pressure of the intake air is easily affected by other factors other than the failure of the EGR device, if the negative pressure of the intake air is affected by other factors, the failure of the EGR device is erroneously detected. The possibility increases.

  Further, the technology of Patent Document 2 cannot detect a failure of the EGR device unless the operating internal combustion engine (engine) is stopped unintentionally (engine stop state).

  The present invention has been made in consideration of the above-mentioned various problems. By estimating the valve opening of the EGR device without using a lift sensor, the EGR device can be accurately controlled and the cost can be reduced. An object of the present invention is to provide an EGR system that can be used. Another object of the present invention is to provide an EGR system that can improve the accuracy of detecting a failure of an EGR device.

  The present invention includes an exhaust gas recirculation unit that connects an intake system and an exhaust system of an internal combustion engine, and an EGR device provided in the exhaust gas recirculation unit, and the intake system and the exhaust system are connected via the EGR device. The EGR system is configured such that a part of the exhaust gas discharged from the internal combustion engine is recirculated from the exhaust system to the intake system via the exhaust recirculation means.

The EGR system according to the present invention achieves the above-described object,
The EGR device has a valve for controlling the flow rate of the exhaust gas,
The EGR system
An intake state detection means capable of detecting an intake state of the intake system;
Intake air amount detection means for detecting the amount of intake air sucked into the internal combustion engine from the intake system, negative pressure detection means for detecting negative pressure of intake air sucked into the internal combustion engine from the intake system, and / or , A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
The intake air amount detected by the intake air amount detection means, the negative pressure of intake air detected by the negative pressure detection means, and / or the rotation speed detected by the rotation speed detection means, and the intake state detection A valve opening degree estimating means for estimating the opening degree of the valve based on the intake state detected by the means;
It is characterized by further having.

  Thus, according to the present invention, the intake air amount detection means, the negative pressure detection means and / or the rotation speed detection means and the intake air which are existing sensors can be used without using a lift sensor (opening sensor). The valve opening of the EGR device is estimated based on the intake air amount detected using the state detection means, the negative pressure of the intake air and / or the rotational speed and the intake state. Even if there is a possibility that the exhaust gas recirculation amount may decrease due to, for example, adhesion of combustion products resulting from combustion to the valve or the exhaust gas recirculation means, the EGR device can be controlled with high accuracy. At the same time, the cost can be reduced. In addition, it is possible to improve the accuracy of detecting a failure of the EGR device.

  Here, the EGR system determines whether or not the opening degree of the valve estimated by the valve opening degree estimating means exceeds a predetermined threshold value (whether or not it is within a predetermined range), and the opening degree of the valve Is greater than the threshold value (when it exceeds the predetermined range), a determination means for outputting a warning signal indicating a failure of the EGR device, and an external indication that the EGR device has failed based on the warning signal It is preferable to further include warning means for warning (notifying). Thereby, a warning signal is output according to the actual opening of the valve, and the failure of the EGR device can be notified from the warning means to the outside. As a result, it is possible to detect a failure of the EGR device with high reliability. Further, the user (driver) can immediately know that the EGR device has failed based on the notification content from the warning means, and promptly perform necessary failure countermeasures such as replacement of the EGR device. Is possible.

  In addition, when there is a possibility that the EGR device may break down due to adhesion of combustion products to the valve, a failure elimination mode for eliminating the adhesion of combustion products, etc. by fully opening and closing the valve. It is desirable to implement. In order to implement such a failure elimination mode, the EGR system further includes a signal output means for outputting a signal for causing the valve to be fully opened and fully closed to the EGR device, and the signal output means includes an estimation In a case where the opening degree of the valve thus made is larger than a predetermined first threshold value, it is preferable to change the number of times the signal is output in accordance with the estimated opening degree of the valve.

  In this case, if the opening degree of the valve is larger than the first threshold value that is a criterion for occurrence of failure of the EGR device, the number of times the signal is output is changed according to the opening degree of the valve, thereby Resolution mode can be implemented. This makes it possible to shorten the energization time required to fully open and fully close the valve, compared to the case where the valve is fully opened and fully closed a fixed number of times regardless of the opening of the valve. In this way, power consumption of the EGR system can be realized by eliminating waste of the energization time. In particular, if the failure elimination mode is executed when the operation of the internal combustion engine is stopped, it is possible to avoid deterioration of emissions due to mixing of the exhaust gas containing the combustion products into the internal combustion engine. Product adhesion and the like can be effectively eliminated.

  In addition, the EGR system may cause the EGR device to fail when the estimated opening of the valve becomes greater than a predetermined second threshold after the signal is output by the signal output means a predetermined number of times. It is preferable to further have a warning means for warning that there is. In this case, the second threshold value is a threshold value corresponding to the degree of opening at which the adhesion of the combustion products cannot be eliminated even when the failure elimination mode is performed. Therefore, even if the failure elimination mode is executed, if the valve opening is larger than the second threshold value, the warning means always gives a warning, so that the failure of the EGR device and the cause of the failure can be easily identified. can do.

  In this case, the intake air amount detection means, the negative pressure detection means, and / or the rotation speed detection means sets the intake air amount, the negative pressure of the intake air, and / or the rotation speed immediately after the start of the internal combustion engine. It is preferable to detect. Thereby, a failure of the EGR device can be detected with high accuracy.

  The intake air condition detecting means is a sensor for detecting the intake air condition of the internal combustion engine, and is preferably the following components.

  That is, the EGR system according to the present invention described above has the following configurations (1) to (5).

  (1) The intake state detection means is a water temperature sensor that detects the temperature of the cooling water in the internal combustion engine, and the valve opening estimation means is a maximum value of the intake air amount (maximum intake air amount), Minimum negative pressure of intake air (minimum value of pressure in the intake system (for example, intake manifold)) and / or maximum value of rotation speed (maximum rotation speed) and temperature of the cooling water detected by the water temperature sensor Is used to estimate the opening of the valve.

  (2) The intake system is provided with a throttle valve for adjusting the amount of intake air taken into the internal combustion engine from the intake system, and the intake state detection means detects the opening of the throttle valve. A throttle opening sensor, wherein the valve opening estimating means uses the maximum intake air amount, the minimum negative pressure and / or the maximum rotation speed and the throttle valve opening detected by the throttle opening sensor; Then, the opening degree of the valve of the EGR device is estimated.

  (3) The intake system is also provided with a secondary gas supply valve for supplying a secondary gas for the intake air to the intake system, and the intake state detection means is provided with the secondary gas supply valve. A secondary gas opening sensor for detecting an opening, wherein the valve opening estimating means includes the maximum intake air amount, the minimum negative pressure and / or the maximum rotation speed and the secondary gas opening sensor. Based on the detected opening of the secondary gas supply valve, the opening of the valve of the EGR device is estimated.

  (4) In the case of the above (3), the secondary gas supply valve is a check that constitutes a blow-by gas reduction device that guides the blow-by gas as the secondary gas generated in the internal combustion engine to the intake system. It is a valve.

  (5) The intake system is provided with a throttle valve for adjusting the amount of intake air taken into the internal combustion engine from the intake system, and a bypass passage that bypasses the throttle valve, and the intake state detection means Is an opening sensor for secondary air that is provided in the bypass passage and detects the opening of an adjustment valve for adjusting the amount of intake air taken into the idle internal combustion engine. The secondary air is part of the intake air supplied to the downstream side of the throttle valve in the intake system via the adjustment valve and the bypass passage.

  In any of the configurations (1) to (5) described above, the intake air amount, the minimum negative pressure and / or the maximum rotational speed and the intake state of the intake system can be detected. The valve opening degree estimating means accurately estimates the opening degree of the valve of the EGR device based on the detected intake air amount, the minimum negative pressure and / or the maximum rotation speed and the intake state. it can.

  The EGR system according to the present invention described above is provided with a control means for recirculating a part of the exhaust gas to the intake system by controlling the EGR device, and detects the air-fuel ratio. An air-fuel ratio detection means, and the control means controls the EGR device to recirculate a part of the exhaust gas to the intake system, and the air-fuel ratio detected by the air-fuel ratio detection means Is within a predetermined range, the valve opening of the EGR device estimated by the valve opening estimating means is preferably corrected to a predetermined value. Thus, the recirculation amount of the exhaust gas can be controlled more accurately by correcting the valve opening of the EGR device in consideration of the air-fuel ratio.

  The EGR system according to the present invention is provided in the exhaust system and sets an injection time of fuel injected from an air-fuel ratio detection means for detecting an air-fuel ratio and a fuel injection means of the internal combustion engine in the intake system. Fuel injection time setting means for performing the injection time setting when the air-fuel ratio detected by the air-fuel ratio detection means is out of a predetermined range. It is preferable to correct it. By correcting the injection time in consideration of the air-fuel ratio, the fuel injection amount from the fuel injection means can be controlled with high accuracy, and the fuel efficiency of the internal combustion engine is improved.

  According to the present invention, the following effects can be obtained.

  That is, without using a lift sensor (opening sensor), an intake air amount detected by using an intake air amount detecting means, a negative pressure detecting means and / or a rotation speed detecting means and an intake state detecting means, which are existing sensors. Since the opening of the valve of the EGR device is estimated based on the negative pressure of the intake air and / or the rotational speed of the internal combustion engine and the intake state, the valve of the combustion product resulting from the combustion of the internal combustion engine and the exhaust gas recirculation Even if the exhaust gas recirculation amount may decrease due to adhesion to the means, the EGR device can be accurately controlled and the cost can be reduced. In addition, it is possible to improve the accuracy of detecting a failure of the EGR device.

It is a schematic structure explanatory view of an EGR system concerning this embodiment. 2A and 2B are flow charts for explaining an estimation operation of the valve opening of the EGR device, a failure detection operation of the EGR device, and a feedback control process for the air-fuel ratio, respectively. 3A to 3C are maps for estimating the valve opening (lift amount) of the EGR device used in the flowchart of FIG. 2A. 4A is a map for calculating the duty of the EGR control signal supplied to the EGR device, and FIG. 4B is a map for calculating the energization time of the injector control signal supplied to the injector. Is a map for correcting the duty of FIG. 4A, and FIG. 4D is a map for correcting the energization time of FIG. 4B. FIG. 5A is a flowchart for explaining the execution of the failure elimination mode for the valve of the EGR device, and FIG. 5B is for determining the number of times of full opening and closing of the valve from the lift amount used in the flowchart of FIG. 5A. It is a map of.

  Preferred embodiments of the EGR system according to the present invention will be described below and described in detail with reference to the accompanying drawings.

[Configuration of this embodiment]
In FIG. 1, an EGR system 10 according to the present embodiment is provided with an intake device (intake system) 14 and an exhaust device (exhaust system) 16 in an engine (internal combustion engine) 12, and the intake device 14 and the exhaust device 16 are connected to EGR. In a configuration in which the EGR device 20 is provided in the middle of the EGR passage 18 by connecting with the passage (exhaust gas recirculation means) 18, the intake device 14 and the exhaust device 16 are communicated with each other by controlling the EGR device 20. A part of the exhaust gas discharged from the exhaust gas is recirculated to the intake device 14 and diagnoses whether the EGR device 20 is faulty. In FIG. 1, a multi-cylinder engine 12 having a plurality of cylinders, and an intake device 14 and an exhaust device 16 connected to the engine 12 are schematically illustrated. Further, the EGR device 20 includes a valve 24 attached to the tip of the shaft 22, and the intake device 14 and the exhaust device 16 can communicate with each other by displacing the shaft 22 to open the valve 24. .

  Here, the engine 12, the intake device 14, and the exhaust device 16 to which the EGR system 10 is applied will be described.

  The engine 12 is mounted on a vehicle such as an automobile or a motorcycle, for example, and a plurality of cylinder chambers 32 are formed inside the engine body 30. Each cylinder chamber 32 is provided with a piston 34 that can be displaced along the axial direction. That is, the strokes of the piston 34 cause intake, compression, combustion, and exhaust strokes in the engine 12. Then, the driving force of the engine 12 is output from the piston 34 via the connecting rod 36 and the crankshaft 38. In FIG. 1, only one cylinder chamber 32 is shown.

  An intake port 40 and an exhaust port 42 are opened in the combustion chamber 39 formed above the cylinder chamber 32. The intake port 40 is provided with an intake valve 44, while the exhaust port 42 is provided with an exhaust valve 46. An ignition plug 48 is provided for each combustion chamber 39 above the combustion chamber 39 between the intake port 40 and the exhaust port 42.

  Further, a water jacket 50 is formed in the engine main body 30, and the piston 34 and the like of the engine 12 can be cooled by circulating cooling water between a radiator (not shown) and the water jacket 50.

  Further, the engine 12 is provided with a blow-by gas reduction device (PCV) 52 for guiding blow-by gas (secondary gas) generated in the cylinder chamber 32 to the intake device 14.

  The PCV 52 communicates with the cylinder chamber 32, and includes a gas passage 54 through which blow-by gas passes, a chamber 56 formed in the vicinity of the intake port 40 and the exhaust port 42 on the downstream side of the gas passage 54, and blow-by gas from the chamber 56 as an engine. 12 includes a check valve (secondary gas supply valve) 58 for discharging to the outside and a gas passage 59 for connecting the chamber 56 to the tank portion 64 of the intake device 14 via the check valve 58. Accordingly, the blow-by gas is introduced from the cylinder chamber 32 through the gas passage 54, the chamber 56, the check valve 58 and the gas passage 59 to the intake device 14, and the intake air taken into the intake device 14 from the outside through the air cleaner 72. At the same time, the air is sucked into the intake port 40.

  Each intake port 40 is connected to an intake branch pipe 62 of an intake manifold 60 constituting the intake device 14. The intake manifold 60 is formed so as to be connected to each intake branch pipe 62 and each intake branch pipe 62 formed in a branch shape so as to branch into a plurality of pipes on the engine 12 side as the downstream side, and has a predetermined capacity. The tank portion 64 is formed on the upstream side of the tank portion 64 and includes an intake manifold 66 that collects the intake branch pipes 62. As described above, since only one cylinder chamber 32 is illustrated in FIG. 1, only one intake branch pipe 62 is illustrated for the intake manifold 60.

  The intake manifold 66 is provided with a throttle body 70 including a throttle valve 68 that opens and closes in response to an operation of an accelerator pedal (not shown). An air cleaner 72 is provided on the upstream side of the throttle body 70, and intake air is taken into the intake manifold 60 from the outside through the air cleaner 72. In this case, dust or the like contained in the intake air is suitably removed by the air cleaner 72.

  Each intake branch pipe 62 is provided with an injector (fuel injection means) 74 for injecting fuel so as to face the intake port 40. Note that the present invention is also applicable to a direct injection engine in which the injector 74 is disposed directly in the combustion chamber 39.

  Further, an idle speed control device 76 is provided in the intake manifold 66 so as to bypass the throttle body 70. The idle speed control device 76 is provided in the bypass passage 78 that bypasses the throttle valve 68 and the bypass passage 78, and an adjustment valve (IACV, two for adjusting the amount of intake air taken into the engine 12 in the idle state. Secondary air supply valve) 79. Therefore, when the throttle valve 68 is closed, the intake air (secondary air) flows through the bypass passage 78 and the adjustment valve 79 to the downstream side of the throttle valve 68 in the intake manifold 66.

  On the other hand, an exhaust branch pipe 82 of an exhaust manifold 80 constituting the exhaust device 16 is connected to each exhaust port 42. The exhaust manifold 80 includes exhaust branch pipes 82 that are formed in a branch shape so as to branch into a plurality of pipes on the engine 12 side as the upstream side, and exhaust collecting pipes 84 that collect the exhaust branch pipes 82. The exhaust collecting pipe 84 is provided with a catalyst 86 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas exhausted from each exhaust port 42 by the exhaust stroke of the engine 12. In FIG. 1, only one exhaust branch pipe 82 is shown for the exhaust manifold 80.

  The upstream side of the exhaust collecting pipe 84 and the downstream side of the intake branch pipe 62 are connected by an EGR passage 18. The EGR passage 18 connects an exhaust side exhaust gas recirculation pipe 90 extending from the upstream side of the exhaust collecting pipe 84 to the input port 92 of the EGR device 20 and also connects an intake side exhaust gas recirculation pipe 94 extending from the downstream side of the intake branch pipe 62 to the EGR. It is configured by connecting to the output port 96 of the device 20.

  In the EGR device 20, when the shaft 22 is displaced in the axial direction and the valve 24 is separated from the input port 92, the valve is opened, and a part of the exhaust gas is discharged from the exhaust collecting pipe 84 to the exhaust side exhaust recirculation pipe. 90, the air can be recirculated to the intake branch pipe 62 via the EGR device 20 and the intake side exhaust recirculation pipe 94. As a result, when the fuel is injected from the injector 74 to the exhaust gas recirculated to the intake device 14 and the intake air and blow-by gas from the upstream side of the intake device 14, the fuel and intake air near the intake port 40. Then, an air-fuel mixture is formed by mixing the recirculated exhaust gas and blow-by gas, and the air-fuel mixture can be sucked into the combustion chamber 39 during the intake stroke of the engine 12. If the valve 24 closes the input port 92 due to the displacement of the shaft 22 in the axial direction, the EGR device 20 is closed, and the communication state between the exhaust collecting pipe 84 and the intake branch pipe 62 is shut off ( The exhaust gas recirculation operation stops).

  In FIG. 1, the engine 12, the intake device 14, and the exhaust device 16 include various states related to the intake system, that is, the intake state of the intake device 14, the negative pressure PB of the intake air, the intake air amount AFMQAIR, and / or Alternatively, in order to detect the engine rotational speed (the rotational speed of the internal combustion engine) NE, the following detection means is provided.

  An air flow meter (intake air amount detection means) 100 as a sensor for detecting the amount of intake air (intake air amount AFMQAIR) taken into the intake manifold 66 through the air cleaner 72 from the outside is provided in the intake manifold 66 of the intake device 14. Is provided. Further, the tank portion 64 is provided with a negative pressure sensor (negative pressure detecting means) 102 for detecting the negative pressure PB of the intake air taken into the combustion chamber 39 of the engine 12 from the intake device 14 during the intake stroke of the engine 12. It has been. Further, the throttle body 70 is provided with a throttle opening sensor 130 that detects the opening of the throttle valve 68. Further, the idle speed control device 76 is provided with an IACV opening sensor (secondary air opening sensor) 132 for detecting the opening of the IACV 79. In the following description, the air flow meter 100 is also referred to as a sensor 100.

  The engine 12 is provided with an engine speed sensor (rotation speed detecting means) 104 (for example, a crank position sensor) that detects the engine speed NE based on the crank angle of the crankshaft 38. The engine body 30 is provided with a water temperature sensor 106 that detects the temperature of the cooling water in the water jacket 50 (water temperature TW). Further, the engine body 30 is also provided with a check valve opening sensor (secondary gas opening sensor) 134 for detecting the opening of the check valve 58.

  The exhaust collecting pipe 84 of the exhaust device 16 is provided with a wide area air-fuel ratio sensor (LAF sensor) 108 as an air-fuel ratio detecting means capable of linearly detecting an air-fuel ratio LAF over a wide range from lean to rich with respect to the exhaust gas. ing. Since the LAF sensor 108 detects the air-fuel ratio LAF based on the oxygen concentration in the exhaust gas, the LAF sensor 108 may be provided in the exhaust side exhaust gas recirculation pipe 90 into which a part of the exhaust gas flows.

  Detection results (indicating detection signals) of these sensors 100 to 108 and 130 to 134 are output to an engine control unit (ECU) 110.

  The ECU (valve opening estimation means, determination means, signal output means) 110 is based on the detection results of the sensors 100 to 108 and 130 to 134 described above, the engine 12, the EGR device 20, the ignition plug 48, and the check valve. 58, the throttle valve 68, the injector 74, the IACV 79, and the like. The ECU 110 also includes a memory 112 that stores various types of information and an estimation process for estimating the opening degree of the valve 24 (the lift amount of the valve 24 with respect to the input port 92 due to the movement of the shaft 22 in the axial direction). Further, various maps 138 to 144 used for failure diagnosis processing of the EGR device 20, various maps 146 to 152 used for feedback control with respect to the air-fuel ratio LAF, and the valve 24 of the combustion product resulting from the combustion of the engine 12 When there is a possibility that the EGR device 20 may break down due to adhesion to the gas, etc., there is a map 154 that is used when performing a failure elimination mode for eliminating adhesion of combustion products and the like.

  In this case, the ECU 110 estimates and estimates the lift amount of the valve 24 when the EGR device 20 is not in operation using the detection results of the sensors 100 to 106 and the maps 138, 140, and 144. The presence or absence of a failure of the EGR device 20 is diagnosed based on the lift amount. Further, when the estimated lift amount is not 0 (when the valve is not closed), the ECU 110 uses the lift amount and the map 142 to use the EGR control signal duty correction amount Open_Duty supplied to the EGR device 20. To decide. Further, when it is determined that a failure has occurred in the EGR device 20 as a result of performing the failure diagnosis process on the EGR device 20, a failure warning lamp (MIL) serving as a warning means indicates a warning signal indicating the occurrence of the failure. It outputs to 122. The MIL 122 notifies the outside (driver) of the occurrence of a failure of the EGR device 20 based on the warning signal.

  When performing feedback control on the air-fuel ratio LAF, the ECU 110 corrects the duty of the EGR control signal using the detection results of the sensors 102 to 108, the maps 146 to 152, and the duty correction amount Open_Duty. The injection time of the fuel injected from the injector 74 (the energization time supplied to the injector 74 to the injector 74) is corrected.

  Therefore, the EGR system 10 according to the present embodiment includes the EGR passage 18 and the EGR device 20 described above, the sensors 100 to 108 and 130 to 134, the ECU 110 (and each component in the ECU 110), and the MIL 122. Composed.

  In addition, the following (1) to (3) are the main causes of failure of the EGR device 20 that needs to perform the failure elimination mode described above. That is, (1) foreign matter biting in which foreign matter is sandwiched between the valve 24 and a valve seat (not shown), and (2) combustion products locally accumulate on at least one of the valve 24 and the seat surface of the valve seat. And (3) a stick in which a combustion product adheres between the shaft 22 and a bearing (not shown) and the shaft 22 does not move.

  Therefore, in the EGR system 10, in order to eliminate the cause of failure of the EGR device 20 such as foreign matter biting, deposit, stick, etc., when the operation of the engine 12 is stopped (when the ignition switch is turned off), the valve 24 is fully opened. The failure elimination mode for removing foreign objects, deposits, and sticks is performed by repeatedly executing and fully closing.

  Specifically, the ECU 110 has a map 154 that shows the relationship between the lift amount of the valve 24 and the number of times that the valve 24 is fully opened and fully closed. Therefore, if the estimated lift amount of the valve 24 is larger than a predetermined first threshold value that is a criterion for determining the occurrence of the failure of the EGR device 20, the ECU 110 refers to the map 154 and resolves the failure from the estimated opening degree of the valve 24. The number of executions of fully opening and closing the valve 24 when the mode is executed is determined, and an EGR control signal corresponding to the determined number of executions is supplied to the EGR device 20.

  In this case, the EGR control signal is a pulse signal having a full duty of 100% for the fully open operation of the valve 24 and a duty of 0% for the fully closed operation. In other words, the EGR control signal is a signal composed of pulses corresponding to the number of times that the valve 24 is fully opened and fully closed. Therefore, the EGR device 20 can cause the valve 24 to be fully opened and closed by the number of executions in accordance with the pulse of the EGR control signal.

  Further, if the lift amount of the valve 24 estimated after the above-described failure elimination mode is greater than a predetermined second threshold value indicating the lift amount when failure causes such as deposits cannot be eliminated, the ECU 110 determines that the failure elimination mode. It is determined that the cause of the failure could not be resolved even if the operation is performed, and a warning signal indicating the determination result is output to the MIL 122. Based on the warning signal, the MIL 122 notifies the driver that the EGR device 20 has failed and the cause of the failure has not been resolved.

  The first threshold value and the second threshold value may be the same value or different values.

[Operation of this embodiment]
The EGR system 10 according to the present embodiment is configured as described above. Next, the operation of the EGR system 10 will be described with reference to FIGS. 2A to 5B. In addition, in this description, it demonstrates, also referring FIG. 1 as needed.

  FIG. 2A is a flowchart of the lift amount estimation processing of the valve 24 of the EGR device 20 and the failure diagnosis processing of the EGR device 20 by the EGR system 10. FIG. 2B is a flowchart of feedback control processing for the air-fuel ratio LAF.

  First, the estimation process of the lift amount of the valve 24 of the EGR device 20 and the failure diagnosis process of the EGR device 20 by the EGR system 10 will be described with reference to FIGS. 2A and 3A to 3C.

  In step S1 of FIG. 2A, when the driver turns on an ignition switch (not shown), the water temperature sensor 106 detects the water temperature TW of the cooling water in the water jacket 50 and outputs a detection signal indicating the water temperature TW to the ECU 110 ( Step S2).

  When the engine 12 starts to start in step S3, the air flow meter 100 sequentially detects the intake air amount AFMQAIR, outputs a detection signal indicating the intake air amount AFMQAIR to the ECU 110, and the negative pressure sensor 102 detects the intake air amount. The negative pressure PB is sequentially detected and a detection signal indicating the negative pressure PB is output to the ECU 110, and the engine speed sensor 104 sequentially detects the engine speed NE and outputs a detection signal indicating the engine speed NE to the ECU 110. Output to. Note that the ECU 110 does not set an engine stop flag indicating that the operation of the engine 12 is stopped when the engine 12 is started (engine stop flag = 0). The engine stop flag is stored in the memory 112.

  By the way, when the engine 12 starts to start, the intake air amount AFMQAIR increases rapidly in a short time, reaches the maximum intake air amount MAX_AFMQAIR, and then rapidly decreases and settles to a substantially constant value. Further, the negative pressure PB also decreases rapidly after a short time after the start of the engine 12, and then reaches the minimum negative pressure MIN_PB (minimum value of the pressure in the intake device 14 (for example, the intake manifold 60)). It rises rapidly and settles to a nearly constant value. Further, the engine speed NE also increases rapidly in a short time after the start of the engine 12 and then reaches the maximum engine speed MAX_NE (maximum value of the engine speed NE). Settling to a certain value.

  On the other hand, the recirculation amount of the exhaust gas recirculated from the exhaust device 16 to the intake device 14 is reduced due to adhesion of combustion products resulting from the combustion of the engine 12 to the EGR passage 18 and the valve 24. As a result, even if the ECU 110 attempts to recirculate the exhaust gas having a desired recirculation amount to the intake device 14 by controlling the EGR device 20, the desired recirculation amount and the actual recirculation amount are different.

  Further, if the valve 24 of the EGR device 20 that should be in a closed state is open due to adhesion of combustion products to the valve 24, the intake device 14 takes in the intake air from the outside. Air may leak into the EGR passage 18 and the EGR device 20. Therefore, when such a leak occurs in the non-operating region of the EGR device 20, the minimum negative pressure MIN_PB increases (the absolute value of the minimum negative pressure MIN_PB) as compared to the valve closed state (normal time) of the EGR device 20. The maximum intake air amount MAX_AFMQAIR may decrease, or the maximum engine speed MAX_NE may decrease.

  Therefore, in step S4, the ECU 110 detects from the air flow meter 100 the detection signal indicating the maximum intake air amount MAX_AFMQAIR, the detection signal indicating the minimum negative pressure MIN_PB from the negative pressure sensor 102, and / or the maximum engine speed from the engine speed sensor 104. When a detection signal indicating the number MAX_NE is input, the maximum intake air amount MAX_AFMQAIR, the minimum negative pressure MIN_PB, and / or the maximum engine speed MAX_NE are stored in the memory 112.

  In the next step S5, the ECU 110 determines the lift amount of the valve 24 according to the minimum negative pressure MIN_PB and the water temperature TW with reference to the map 140, or refers to the map 144 with the maximum intake air amount MAX_AFMQAIR and the water temperature. The lift amount of the valve 24 corresponding to TW is determined, or the lift amount of the valve 24 corresponding to the maximum engine speed MAX_NE and the water temperature TW is determined with reference to the map 138.

  FIG. 3A is a graph showing the relationship between the water temperature TW, the minimum negative pressure MIN_PB, and the lift amount shown in the map 140. In this graph, a plurality of solid lines (curves) are curves showing the relationship between the water temperature TW and the minimum negative pressure MIN_PB for each lift amount of different valves 24, and the water temperature TW is controlled in the control of the various valves 24 described above. Therefore, if the water temperature TW is the same, it is considered that the intake states are substantially the same. In particular, as the lift amount of the valve 24 increases, the minimum negative pressure MIN_PB increases (the absolute value of the minimum negative pressure MIN_PB). Becomes smaller).

  FIG. 3B is a graph showing the relationship between the water temperature TW, the maximum intake air amount MAX_AFMQAIR, and the lift amount shown in the map 144. Similarly, in this graph, a plurality of solid lines (curves) are curves indicating the relationship between the water temperature TW and the maximum intake air amount MAX_AFMQAIR for each different lift amount. If the water temperature TW is the same, the lift amount increases. The maximum intake air amount MAX_AFMQAIR decreases.

  Further, FIG. 3C is a graph showing the relationship between the water temperature TW, the maximum engine speed MAX_NE, and the lift amount shown in the map 138. Similarly, in this graph, a plurality of solid lines (straight lines) are straight lines showing the relationship between the water temperature TW and the maximum engine speed MAX_NE for each different lift amount. If the water temperature TW is the same, the lift amount increases. The maximum engine speed MAX_NE decreases.

  Accordingly, in step S5, the ECU 110 specifies a curve or a straight line corresponding to the detected water temperature TW and the minimum negative pressure MIN_PB, the detected water temperature TW and the maximum intake air amount MAX_AFMQAIR, or the detected water temperature TW and the maximum engine speed MAX_NE. Then, the lift amount indicated by the curve or straight line is specified as the lift amount Open_Lift of the valve 24 in the non-operating EGR device 20 immediately after the start of the engine 12. The identified lift amount Open_Lift is stored in the memory 112.

  In step S6, the ECU 110 determines whether or not the lift amount Open_Lift is 0 (whether or not the valve 24 is closed).

  When Open_Lift = 0, the ECU 110 diagnoses that the EGR device 20 has not failed because the valve 24 is in the closed state, and does not set the current failure flag indicating the current failure diagnosis result (current failure flag = 0), the current failure flag is stored in the memory 112 (step S7).

  On the other hand, when Open_Lift is not 0 but within a predetermined range in Step S6 (Step S6: NO, Step S8: YES), for example, when “0 <Open_Lift <predetermined threshold value”, ECU 110 in Step S9. Diagnoses that the valve 24 is slightly open but the lift amount is not enough to determine a failure, does not set the current failure flag (current failure flag = 0), and stores the current failure flag in the memory 112. .

  As a result, in the next step S10, the ECU 110 refers to the map 142 and determines the duty correction amount Open_Duty (hereinafter, also referred to as duty Open_Duty) of the EGR control signal according to the lift amount Open_Lift. The determined duty Open_Duty is also stored in the memory 112. The duty Open_Duty is a duty that indicates an offset amount with respect to the predetermined duty when the EGR control signal having a predetermined duty is supplied to the EGR device 20 in the valve closed state to shift the valve 24 to the valve open state. .

  In step S8, if the lift amount Open_Lift is out of a predetermined range (first threshold, second threshold) (step S8: NO), that is, if “Open_Lift ≧ predetermined threshold”, in step S11. The ECU 110 diagnoses that the lift amount is such that it can be determined as a failure, sets the current failure flag (current failure flag = 1), and stores the current failure flag in the memory 112.

  By the way, the current failure flag stored in the memory 112 in steps S7, S9, and S11 all indicates the current failure diagnosis result. Therefore, when the process of FIG. 2A is executed, the current failure flag already stored in the memory 112 is diagnosed in the previous process and the current failure flag in the previous process stored in the memory 112 (hereinafter, It is also referred to as “previous failure flag”.

  As will be described in detail with reference to FIGS. 5A and 5B, when the previous failure flag = 0 and the current failure flag = 1, the EGR system 10 starts immediately after the operation of the engine 12 stops and before the next processing in FIG. 2A starts. When the operation of the engine 12 is stopped until before the next operation of the engine 12 is started, a failure elimination mode for the purpose of eliminating deposits or the like is performed.

  Therefore, if the previous failure flag = 1 in the previous processing of FIG. 2A, the failure elimination mode is set when the operation of the engine 12 is stopped immediately after the previous operation stop of the engine 12 until before the current processing start of FIG. 2A. Has already been implemented.

  Therefore, in the next step S12, the ECU 110 determines whether or not the previous failure flag = 0. If the previous failure flag = 0 (step S12: YES), the ECU 110 has the current failure flag = 1 (step S11), although no failure of the EGR device 20 has occurred at the previous stage of FIG. 2A. Therefore, after the operation of the engine 12 is stopped, it is determined to execute the failure elimination mode of FIGS. 5A and 5B. That is, in the case of the previous failure flag = 0, in the current failure diagnosis processing in step S8 in the processing of FIG. 2A, the lift amount Open_Lift is larger than a threshold value (first threshold value) that is a criterion for performing the failure elimination mode. This is a process for determining whether or not.

  On the other hand, in step S12, if the previous failure flag = 1 (step S12: NO), the ECU 110 also has the current failure flag = 1 (step S11), so the failure resolution performed prior to the current processing of FIG. 2A is performed. It is determined that the deposit has not been resolved depending on the mode. That is, in the case where the previous failure flag = 1, the failure diagnosis processing in step S8 in the current processing of FIG. 2A has not been able to eliminate deposits or the like even by performing the previous failure elimination mode. This is a process of determining whether or not the amount Open_Lift is larger than a threshold value (second threshold value) that is a criterion for determining the failure of the EGR device 20.

  If the previous failure flag = 1 and the current failure flag = 1, ECU 110 then outputs a warning signal indicating failure of EGR device 20 to MIL 122. The MIL 122 notifies the outside that a failure has occurred in the EGR device 20 based on the warning signal. As a result, the driver determines that the deposit or the like has not been resolved even if the failure resolution mode is executed (the failure of the EGR device 20 has not been resolved), turns off the ignition switch, and replaces the EGR device 20. It is possible to promptly take measures against failure.

  Note that even if the previous failure flag = 1, if the current failure flag = 0, the deposit or the like has been eliminated by performing the failure elimination mode, so of course the notification by the MIL 122 is not performed. It is.

  Further, there are relationships shown in FIGS. 3A to 3C among the lift amount Open_Lift, the minimum negative pressure MIN_PB, the maximum intake air amount MAX_AFMQAIR, and the maximum engine speed MAX_NE. Therefore, when the lift amount Open_Lift exceeds a predetermined threshold value (when a leak that exceeds the threshold value occurs in the EGR device 20), the detected minimum negative pressure MIN_PB is equal to the negative pressure PB corresponding to the threshold value. The detected maximum intake air amount MAX_AFMQAIR is smaller than the value of the intake air amount AFMQAIR corresponding to the threshold value, or the detected maximum engine speed MAX_NE is equal to the engine speed value corresponding to the threshold value. It can also be determined that the value has become lower than the value of NE.

  Further, as shown in FIGS. 3A to 3C, the values of the minimum negative pressure MIN_PB, the maximum intake air amount MAX_AFMQAIR, and the maximum engine speed MAX_NE change depending on the water temperature TW, so that the ECU 110 sets a threshold value according to the water temperature TW. May be changed.

  Further, after the processing of FIG. 2A, when the driver turns off the ignition switch and the engine 12 stops operating, the ECU 110 sets an engine stop flag (engine stop flag = 1). The engine stop flag is stored in the memory 112.

  Next, feedback control processing for the air-fuel ratio LAF will be described with reference to FIGS. 2B and 4A to 4D. The feedback control process is a process performed after a predetermined time has elapsed from the lift amount Open_Lift estimation process and the failure diagnosis process in FIG. 2A.

  In step S20 of FIG. 2B, if the water temperature TW is a temperature at which the EGR device 20 can be operated (step S20: YES), the ECU 110 detects the engine rotational speed NE detected by the engine rotational speed sensor 104 in the next step S21. The negative pressure PB of the intake air detected by the negative pressure sensor 102 is stored in the memory 112. The temperature is such that the EGR device 20 operates stably and the LAF sensor 108 is activated.

  In the next step S22, the ECU 110 refers to the map 150, and the current engine speed NE and the negative pressure PB stored in the memory 112 are data in a region where the EGR device 20 can operate stably. It is determined whether or not.

  4A illustrates the details of the map 150. In the map 150, columns D1 to D6 are regions in which the EGR device 20 can be stably operated, and other columns “0”. Is a region where the stable operation of the EGR device 20 cannot be achieved. Accordingly, if the field corresponding to the current engine speed NE and the negative pressure PB is any one of D1 to D6 in the map 150 (step S22: YES), the ECU 110 sets the corresponding field in step S23. The stored duty Di (i = 1 to 6) is set as the duty Ini_Duty (its initial value) of the EGR control signal supplied to the EGR device 20.

  In the next step S24, the ECU 110 subtracts the duty Open_Duty from the duty Ini_Duty and calculates the duty after the subtraction (Ini_Duty-Open_Duty) when the duty Open_Duty as the offset amount is calculated in the above-described estimation process of the lift amount Open_Lift. Is supplied to the EGR device 20. Therefore, in the EGR device 20, when an EGR control signal having a duty of (Ini_Duty-Open_Duty) is supplied, a solenoid (not shown) is excited, the shaft 22 is displaced in the axial direction, and the valve 24 is moved from the valve closed state to the valve closed state. Change to open state.

  Therefore, even if combustion products resulting from the combustion of the engine 12 adhere to the EGR passage 18 or the valve 24, the lift amount of the valve 24 is accurately adjusted to the lift amount corresponding to the duty (Ini_Duty-Open_Duty). Since it becomes possible to control, a part of the exhaust gas discharged from the engine 12 can be reliably recirculated from the exhaust device 16 to the intake device 14 via the EGR passage 18 and the EGR device 20.

  On the other hand, in step S25, the ECU 110 refers to the map 152, and the fuel injection time from the injector 74 according to the current engine speed NE and the negative pressure PB stored in the memory 112, more specifically, the ECU 110 The duty Ini_Ti indicating the energization time of the injector control signal corresponding to the injection time supplied to the injector 74 is specified.

  FIG. 4B illustrates the details of the map 152. In the map 152, the columns Ti1 to Ti6 correspond to the columns D1 to D6 in FIG. 4A described above. The other “1” columns correspond to the “0” columns in FIG. 4A. Therefore, the ECU 110 uses the duty Tij (j = 1 to 6) stored in the corresponding column in the map 152 as the duty Ini_Ti (initial value) indicating the energization time of the injector control signal supplied to the injector 74. Set. As a result, when an injector control signal with an Ini_Ti duty is supplied from the ECU 110 to the injector 74, the injector 74 can inject fuel for an injection time corresponding to the duty Ini_Ti (the energization time).

  On the other hand, the LAF sensor 108 has already been activated, sequentially detects the air-fuel ratio LAF, and outputs a detection signal to the ECU 110. In step S26, the ECU 110 stores the air-fuel ratio LAF indicated by the detection signal from the LAF sensor 108 in the memory 112. In the next step S27, the ECU 110 stores the actual air-fuel ratio LAF and the stoichiometric air-fuel ratio (stored in the memory 112). For example, the deviation ΔAF (ΔAF = LAF−14.7) with respect to 14.7) is calculated.

  In the next step S28, ECU 110 determines whether or not deviation ΔAF is within a predetermined range (for example, within the range of the double-headed arrow shown in FIG. 4C).

  In step S28, if deviation ΔAF is within a predetermined range, ECU 110 refers to map 146, and the correction amount of the duty of the EGR control signal supplied to EGR device 20 such that deviation ΔAF becomes zero AF_Duty is calculated (step S29).

  FIG. 4C is a graph showing the relationship between the deviation ΔAF and the correction amount AF_Duty shown in the map 146. If there is a deviation ΔAF within the range of the double arrow, ECU 110 specifies correction amount AF_Duty corresponding to deviation ΔAF.

  Then, the ECU 110 adds the correction amount AF_Duty to the duty of the EGR control signal supplied to the current EGR device 20 (for example, (Ini_Duty-Open_Duty) described above) to correct the duty. The new EGR control signal which has is supplied to the EGR apparatus 20 (step S30). As a result, the EGR device 20 opens and closes the valve 24 according to the corrected duty, so that the lift amount of the valve 24 changes to a lift amount corresponding to (duty before correction + AF_Duty). As a result, the air-fuel ratio LAF detected by the LAF sensor 108 is feedback controlled so as to approach the stoichiometric air-fuel ratio.

  On the other hand, if deviation ΔAF is outside the predetermined range in step S28 (step S28: NO), ECU 110 refers to map 148 and supplies the injector 74 such that deviation ΔAF becomes zero. A duty correction amount AF_Ti of the injector control signal is calculated.

  FIG. 4D is a graph showing the relationship between the deviation ΔAF and the correction amount AF_Ti shown in the map 148. If there is a deviation ΔAF in the range of the arrow, ECU 110 identifies correction amount AF_Ti corresponding to deviation ΔAF.

  Then, the ECU 110 corrects the duty by adding the correction amount AF_Ti to the duty (for example, Ini_Ti described above) indicating the energization time of the current injector control signal supplied to the injector 74, and has the corrected duty. A new injector control signal is supplied to the injector 74 (step S31). As a result, the injector 74 injects fuel at the injection time corresponding to the corrected duty. Even in this case, the air-fuel ratio LAF detected by the LAF sensor 108 is feedback-controlled so as to approach the stoichiometric air-fuel ratio. .

  In step S20 described above, when the water temperature TW has not increased to a temperature at which the EGR device 20 can be operated (step S20: NO), the processes in steps S21 to S31 are not executed.

  In step S32, if the flag is 1 (step S32: NO) as a result of the failure diagnosis processing described with reference to FIG. 2A, the ECU 110 performs failure handling of the EGR device 20 (step S33).

  As described above, the throttle opening sensor 130 detects the opening of the throttle valve 68, the IACV opening sensor 132 detects the opening of the IACV 79, and the check valve opening sensor 134 detects the check. The opening degree of the valve 58 is detected. The intake air amount AFMQAIR is adjusted by the opening of the throttle valve 68 and the opening of the IACV 79, and blow-by gas is discharged from the check valve 58 by the negative pressure PB of the intake air.

  Therefore, in this embodiment, instead of the water temperature TW, the opening degree of the throttle valve 68 detected by the throttle opening degree sensor 130, the opening degree of the IACV 79 detected by the IACV opening degree sensor 132, or the check valve opening degree sensor. The lift amount of the valve 24 may be estimated using the opening degree of the check valve 58 detected by 134. In this case, similarly to FIGS. 3A to 3C, a map showing the relationship between the opening of the throttle valve 68, the opening of the IACV 79, or the opening of the check valve 58 and the water temperature TW for each different lift amount. The lift amount of the valve 24 may be estimated with reference to this map when it is stored in advance in the ECU 110 and the lift amount of the valve 24 is estimated.

  FIG. 5A is a flowchart of a failure elimination mode that is performed when the operation of the engine 12 is stopped after the processing of FIG. 2A. FIG. 5B is an explanatory diagram showing a map 154 used when the failure elimination mode is executed.

  In step S40 of FIG. 5A, the ECU 110 determines whether or not the engine stop flag stored in the memory 112 is “1”. When the engine stop flag = 0 (step S40: NO), the ECU 110 determines that the engine 12 is operating and does not implement the failure elimination mode.

  If the engine stop flag is 1 (step S40: YES), the ECU 110 determines that the engine 12 is stopped, and determines whether or not the current failure flag is 1 in the next step S41. If the current failure flag = 0 (step S41: NO), the ECU 110 determines that no failure has occurred in the EGR device 20, and does not implement the failure elimination mode.

  When the failure flag is 1 at this time (step S41: YES), the ECU 110 determines that the EGR device 20 has been diagnosed as a failure by the process (fault diagnosis process) in FIG. 2A, and executes the failure elimination mode after step S42. Decide what to do.

  Specifically, in step S42, the ECU 110 reads the lift amount Open_Lift estimated by the lift amount estimation process of FIG.

  In the next step S43, the ECU 110 uses the map 154 shown in FIG. 5B to determine the number of executions of repeatedly opening (ON) and fully closing (OFF) the valve 24 from the estimated lift amount Open_Lift.

  In the next step S44, the ECU 110 supplies an EGR control signal indicating the determined number of executions to the EGR device 20. As a result, the EGR device 20 repeatedly opens and closes the valve 24 by the number of executions in accordance with the number of executions of the pulse signal constituting the EGR control signal. As a result, a failure elimination mode for eliminating deposits and the like on the valve 24 and the valve seat is executed.

  In step S44, the supply of the EGR control signal from the ECU 110 to the EGR device 20 causes the valve 24 to be fully opened with 100% full duty, while the valve 24 is fully closed with 0% duty. Thereby, it is possible to eliminate foreign matter biting, deposits, and sticks in the EGR device 20.

  Further, in FIG. 5B, the number of on / off executions is increased in accordance with the lift amount Open_Lift. This is because, for example, when the valve 24 is not closed due to deposit, the deposit amount increases as the lift amount Open_Lift increases. Therefore, it is necessary to increase the number of executions and remove the deposit.

  In step S41 in FIG. 5A, it is determined whether or not the failure elimination mode should be performed using the current failure flag. However, in this embodiment, the failure elimination mode is used using the previous failure flag as necessary. It is also possible to decide whether or not to implement.

[Effect of this embodiment]
As described above, according to the EGR system 10 according to the present embodiment, the intake state of the intake device 14 can be obtained using the existing sensors 100 to 108 and 130 to 134 without using the lift sensor (opening sensor). And the maximum intake air amount MAX_AFMQAIR, the minimum negative pressure MIN_PB and / or the maximum engine speed MAX_NE are detected, and the detected intake state and the maximum intake air amount MAX_AFMQAIR, the minimum negative pressure MIN_PB and / or the maximum engine speed MAX_NE are detected. Since the opening degree of the valve 24 of the EGR device 20 is estimated based on the above, there is a possibility that the recirculation amount of the exhaust gas is reduced due to adhesion of combustion products to the valve 24 and the EGR passage 18 due to combustion of the engine 12. However, the EGR device 20 can be controlled with high accuracy and the cost can be reduced. It can be. In addition, the failure detection accuracy of the EGR device 20 can be increased.

  Further, when the actual lift amount (opening degree) of the valve 24 exceeds a predetermined range, the ECU 110 supplies a warning signal indicating a failure of the EGR device 20 to the MIL 122. Therefore, the failure of the EGR device 20 from the MIL 122 to the outside. Can be reliably notified. As a result, it is possible to detect a failure of the EGR device 20 with high reliability. Further, the driver can immediately know that the EGR device 20 has failed based on the notification content from the MIL 122, and can quickly perform necessary failure countermeasures such as replacement of the EGR device 20. .

  Further, when there is a possibility that the EGR device 20 may break down due to foreign matter biting, deposits, and sticks, a failure elimination mode is implemented in which the valve 24 is fully opened and fully closed to eliminate these causes of failure. . That is, when the lift amount Open_Lift is greater than the first threshold, the ECU 110 determines the number of executions for fully opening and closing the valve 24 from the lift amount Open_Lift using the map 154 in FIG. A corresponding EGR control signal is output to the EGR device 20. That is, the ECU 110 changes the number of executions of full opening and full closing according to the lift amount Open_Lift.

  Thus, in this embodiment, the energization time required for full opening and full closing of the valve 24 can be shortened compared to the case where the valve 24 is fully opened and fully closed a fixed number of times regardless of the lift amount Open_Lift. it can. By eliminating the waste of energization time, it is possible to realize power saving of the EGR system 10.

  In addition, since the failure elimination mode is executed when the operation of the engine 12 is stopped, it is possible to avoid the exhaust gas containing combustion products from being mixed into the engine 12 and deteriorating the emission. As a result, foreign matter biting, deposits, and sticks can be effectively eliminated.

  In addition, after the failure elimination mode is performed, the engine 12 is started and the process of FIG. 2A is performed. As a result, if the lift amount Open_Lift is greater than the second threshold value, the failure elimination mode may be implemented. This means that foreign matter bites, deposits, and sticks could not be eliminated. In such a case, since the MIL 122 notifies the driver of the failure of the EGR device 20, the driver can easily identify the cause of the failure of the EGR device 20.

  Further, in the EGR system 10, immediately after the engine 12 is started, the intake state of the intake device 14 and the maximum intake air amount MAX_AFMQAIR, the minimum negative pressure MIN_PB and / or the maximum engine speed MAX_NE using the sensors 100 to 108 and 130 to 134. Therefore, the failure of the EGR device 20 can be detected promptly.

  Further, in the EGR system 10, when the ECU 110 controls the EGR device 20 to recirculate a part of the exhaust gas to the intake device 14, it is estimated that the air-fuel ratio LAF detected by the LAF sensor 108 is within a predetermined range. The duty of the EGR control signal corresponding to the lift amount of the valve 24 is corrected using AF_Duty. As described above, the duty is corrected in consideration of the air-fuel ratio LAF. Therefore, if the EGR control signal having the corrected duty is supplied to the EGR device 20, the lift amount of the valve 24 can be easily corrected. Further, the recirculation amount of the exhaust gas can be controlled with higher accuracy. As a result, the air-fuel ratio LAF can be brought close to the stoichiometric air-fuel ratio.

  When the air-fuel ratio LAF detected by the LAF sensor 108 is out of the predetermined range, the duty indicating the energization time corresponding to the injection time of the injector 74 is corrected by AF_Ti. In this way, by correcting the duty in consideration of the air-fuel ratio LAF, if the injector control signal having the corrected duty is supplied to the injector 74, the fuel injection time from the injector 74 can be corrected. . As a result, the amount of fuel injected from the injector 74 can be controlled with high accuracy, the fuel consumption of the engine 12 can be improved, and the air-fuel ratio LAF can be brought close to the stoichiometric air-fuel ratio.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... EGR system 12 ... Engine 14 ... Intake device 16 ... Exhaust device 18 ... EGR passage 20 ... EGR device 24 ... Valve 39 ... Combustion chamber 50 ... Water jacket 52 ... PCV
58 ... Check valve 60 ... Intake manifold 74 ... Injector 76 ... Idle speed controller 78 ... Bypass passage 79 ... IACV
DESCRIPTION OF SYMBOLS 80 ... Exhaust manifold 100 ... Air flow meter 102 ... Negative pressure sensor 104 ... Engine speed sensor 106 ... Water temperature sensor 108 ... LAF sensor 110 ... ECU 122 ... MIL
DESCRIPTION OF SYMBOLS 130 ... Throttle opening sensor 132 ... IACV opening sensor 134 ... Check valve opening sensor 138-154 ... Map

Claims (10)

An exhaust gas recirculation unit that connects an intake system and an exhaust system of the internal combustion engine; and an exhaust gas recirculation unit that is provided in the exhaust gas recirculation unit and that communicates the intake system and the exhaust system, thereby In an EGR system having an exhaust gas recirculation device (hereinafter referred to as an EGR device) that recirculates a portion from the exhaust system to the intake system via the exhaust gas recirculation means,
The EGR device has a valve for controlling the flow rate of the exhaust gas,
The EGR system
An intake state detection means capable of detecting an intake state of the intake system;
Intake air amount detection means for detecting the amount of intake air sucked into the internal combustion engine from the intake system, negative pressure detection means for detecting negative pressure of intake air sucked into the internal combustion engine from the intake system, and / or , A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
The intake air amount detected by the intake air amount detection means, the negative pressure of intake air detected by the negative pressure detection means, and / or the rotation speed detected by the rotation speed detection means, and the intake state detection A valve opening degree estimating means for estimating the opening degree of the valve based on the intake state detected by the means;
The EGR system further comprising: The EGR system according to claim 1,
The EGR system further comprising warning means for warning that the EGR device has failed when the estimated opening of the valve is larger than a predetermined threshold value. The EGR system according to claim 1,
Signal output means for outputting a signal for fully opening and closing the valve to the EGR device;
When the estimated opening of the valve is larger than a predetermined first threshold, the signal output means changes the number of times the signal is output according to the estimated opening of the valve. EGR system. The EGR system according to claim 3, wherein
Warning means for warning that the EGR device has failed when the estimated opening of the valve becomes larger than a predetermined second threshold after the signal is output by the signal output means a predetermined number of times. The EGR system further comprising: In the EGR system according to any one of claims 1 to 4,
The EGR system, wherein the intake state detection means is a water temperature sensor that detects a temperature of cooling water in the internal combustion engine. In the EGR system according to any one of claims 1 to 5,
The intake system is provided with a secondary gas supply valve for supplying secondary gas to the intake air to the intake system,
The EGR system, wherein the intake state detection means is a secondary gas opening sensor that detects an opening of the secondary gas supply valve. The EGR system according to claim 6, wherein
The EGR system, wherein the secondary gas supply valve is a check valve constituting a blow-by gas reduction device that guides blow-by gas as the secondary gas generated in the internal combustion engine to the intake system. In the EGR system according to any one of claims 1 to 7,
The intake system is provided with a throttle valve for adjusting the amount of intake air taken into the internal combustion engine from the intake system, and a bypass passage that bypasses the throttle valve,
The intake air state detection means is a secondary air opening sensor that is provided in the bypass passage and detects an opening of an adjustment valve for adjusting an intake air amount sucked into the idle internal combustion engine. An EGR system characterized by that. In the EGR system according to any one of claims 1 to 8,
Control means for recirculating a part of the exhaust gas to the intake system by controlling the EGR device;
An air-fuel ratio detecting means provided in the exhaust system for detecting an air-fuel ratio;
Further comprising
The control means controls the EGR device to recirculate a part of the exhaust gas to the intake system, and if the air-fuel ratio detected by the air-fuel ratio detection means is within a predetermined range, the valve An EGR system, wherein the opening degree of the valve of the EGR device estimated by the opening degree estimation means is corrected to a predetermined value. In the EGR system according to any one of claims 1 to 9,
An air-fuel ratio detecting means provided in the exhaust system for detecting an air-fuel ratio;
Fuel injection time setting means for setting the injection time of fuel injected from the fuel injection means of the internal combustion engine in the intake system;
Further comprising
The fuel injection time setting means corrects the injection time to a predetermined value when the air-fuel ratio detected by the air-fuel ratio detection means is out of a predetermined range.

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