JP4967994B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

  The exhaust gas recirculation control apparatus according to the present invention relates to an exhaust gas recirculation control apparatus for an internal combustion engine, particularly a diesel engine.

In Patent Document 1, an EGR device including an actuator that adjusts an EGR amount and an EGR cooler is a diagnosis target, and any of the EGR amount, the intake fresh air state amount, and the exhaust exhaust state amount is determined based on the detected value of the air flow meter. The actuator was operated so that the deviation calculated between the target value corresponding to the operation area and the corresponding operation reference value of the actuator and the detection result of any amount and the target value was zero. A technique for diagnosing the presence or absence of an abnormality in the EGR cooler based on a comparison between a manipulated variable and a reference value is disclosed.
Japanese Patent Laid-Open No. 2006-242080

  In this Patent Document 1, the EGR decrease due to the decrease in the cooling capacity of the EGR cooler is corrected and controlled by detecting the variation in the intake air amount. However, as shown in FIG. 18, the intake air flow rate is determined by the EGR cooler. Since there is no fluctuation due to a decrease in cooling capacity, there is a problem that a decrease in EGR due to a decrease in cooling capacity of the EGR cooler cannot be corrected.

  In addition, the EGR decrease due to the decrease in the cooling capacity of the EGR cooler is feedback controlled, and the abnormality diagnosis is performed based on the control amount. However, as shown in FIGS. 19 and 20, the decrease in the cooling capacity of the EGR cooler causes the EGR Volume flow does not change.

  That is, in the three EGR coolers of the same type whose cooling capacity has changed with time, as shown in FIG. 19, the temperature drop (delta Temp) of the exhaust gas by passing through the EGR cooler is different. The lower the ability is, the smaller the temperature drop is. On the other hand, there is no change in the volumetric flow rate of EGR between three EGR coolers of the same type whose cooling capacity has changed due to changes over time. Therefore, as shown in FIG. 20, the volumetric efficiency does not change even if the cooling capacity decreases.

  Therefore, since the detected value of the air flow meter does not change, there is a problem that it is impossible to diagnose a decrease in the cooling capacity of the EGR cooler.

  Here, the characteristic line A in FIG. 18, FIG. 19 and FIG. 20 is a characteristic line of an EGR cooler having a normal cooling capacity, that is, an EGR cooler in which the cooling capacity has not been lowered due to aging, and the characteristic line B is a normal line. This is a characteristic line of an EGR cooler in which the cooling capacity is slightly lower than that of a normal one, that is, the cooling capacity is slightly lower than that of a normal one due to a change over time, and the characteristic line C is lower than that of a normal one. This is a characteristic line of an EGR cooler in which the cooling capacity is greatly reduced, that is, the cooling capacity is greatly reduced in comparison with a normal one due to a change with time.

  In addition, since the air flow meter detects the mass flow rate, the detection value varies depending on changes in air temperature and pressure. If the air flow meter itself degrades, changes in the intake system (leakage), or changes in the EGR system (control error in EGR valve opening or clogged passage), the intake air amount changes and the detected value of the air flow meter Changes.

  If the abnormality diagnosis of the air flow meter and the abnormality diagnosis of the EGR system path are not performed separately from the abnormality diagnosis of the EGR cooler (cooling capacity decrease), the abnormality diagnosis of the EGR cooler (cooling capacity decrease) cannot be performed, and the EGR system However, there is a problem that the control accuracy cannot be improved.

  Therefore, as shown in FIG. 1, an exhaust gas recirculation control apparatus for an internal combustion engine according to the present invention includes an operating condition detecting means for detecting an operating condition of the internal combustion engine, and a part of the exhaust gas from the exhaust system of the internal combustion engine. In an internal combustion engine provided with an EGR passage that recirculates to the EGR, an EGR valve provided in the middle of the EGR passage, and an EGR cooler that cools the EGR gas, at least the volume according to the operating condition detected by the operating condition detecting means Control target value setting means for setting an intake air target flow rate (Vair) that is a flow rate, an EGR valve opening target value (EGRdeg), an EGR cooler target heat release amount (Qclr), and a cylinder intake gas target flow rate (Vcyl) that is a volume flow rate An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) which is a volume flow rate, at least detected operating conditions and detected intake air An intake air flow rate reference value (Vair0), which is a volume flow rate, is detected from the flow rate (Vair1), and an abnormality diagnosis of the intake air flow rate detection means is performed using the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0). The EGR cooler heat release amount (Qclr1) from the intake air reference value detection means for performing the operation, the detected operating condition, the detected intake air flow rate (Vair1), and the control target value set by the control target value setting means EGR cooler heat radiation amount detecting means for detecting EGR system path diagnostic means for diagnosing EGR path abnormality from the detected intake air flow rate (Vair1), control target value set by the control target value setting means, EGR cooler diagnosis means for diagnosing an abnormality of the EGR cooler based on the detected EGR cooler heat release amount (Qclr1), E EGR control means for performing opening / closing control of the EGR valve based on the diagnosis result of the GR system path diagnosis means, the diagnosis result of the EGR cooler diagnosis means, and the control target value set by the control target value setting means It is characterized by.

  According to the present invention, the abnormality diagnosis of the intake air flow rate detection means, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler (decrease in cooling capacity) can be performed separately. For this reason, it is possible to diagnose performance deterioration of the intake air flow rate detection means (or leakage from the intake system) and troubles in the EGR system (clogging due to system fouling, deterioration in EGR valve opening control accuracy). Of course, since the cooling capacity decrease due to the EGR cooler being covered with the soot can be diagnosed, the control accuracy of the EGR can be improved according to each diagnosis result or the situation, and the exhaust emission level can be stabilized.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a system configuration diagram of a diesel engine provided with the exhaust gas recirculation control apparatus according to the first embodiment of the present invention, and this diesel engine uses light oil as fuel. FIG. 1 described above also corresponds to a block diagram of the exhaust gas recirculation control apparatus according to the first embodiment of the present invention.

  In FIG. 2, 1 indicates a diesel engine (hereinafter simply referred to as an engine), and 3 indicates an exhaust passage of the engine 1.

  An exhaust outlet passage 3a that constitutes an upstream portion of the exhaust passage 3 of the engine 1 is connected to a turbine 3b of a supercharger, and downstream thereof, PM (particulate matter in exhaust for purification of exhaust gas) A diesel particulate filter (hereinafter referred to as DPF) 16 that collects particulate matter is disposed. The DPF 16 is provided with a NOx trap catalyst and an oxidation catalyst (noble metal) that trap NOx in the exhaust when the exhaust air-fuel ratio is lean and can desorb and purify the trapped NOx when the exhaust air-fuel ratio is rich. You may carry | support and may have the function to remove the exhaust components (NOx, HC, CO) which flow in.

  As an exhaust gas recirculation device, an EGR passage (exhaust gas recirculation passage) 4 for recirculating a part of the exhaust gas is provided between the intake collector 2c of the intake passage 2 and the exhaust outlet passage 3a. An EGR cooler 17 for cooling the exhaust gas is provided on the way. Temperature sensors 36 and 37 are provided in the EGR passage 4 before and after the EGR cooler 17 to detect exhaust temperatures T1 and T2 before and after passing through the EGR cooler 17, respectively. Further, an EGR valve 5 whose opening degree can be continuously controlled by a stepping motor is interposed in the connection portion of the intake collector 2c of the EGR passage 4.

  The intake passage 2 includes an air cleaner 2a at an upstream position, and an air flow meter 7 for detecting the intake fresh air amount Gair and detecting the intake air amount, a temperature sensor 8 for detecting the intake air temperature Tair, and an intake pressure Pair at the downstream thereof. A pressure sensor 9 for detection and a compressor 2b of a supercharger are disposed, and an intake throttle valve 6 that is opened and closed by an actuator (for example, a stepping motor type) is disposed between the compressor 2b and the intake collector 2c. It is intervened.

  The fuel injection device 10 of the engine 1 is a well-known common rail fuel injection device, and generally includes a supply pump 11, a common rail (accumulation chamber) 14, and a fuel injection valve 15 provided for each cylinder. After the fuel pressurized by the supply pump 11 is temporarily stored in the common rail 14 via the fuel supply passage 12, the high-pressure fuel in the common rail 14 is distributed to the fuel injection valve 15 of each cylinder.

  The common rail 14 is provided with a pressure sensor 34 and a temperature sensor 35 in order to detect the pressure Pcr and temperature Tf of the fuel in the common rail 14. Further, in order to control the fuel pressure in the common rail 14, a part of the fuel discharged from the supply pump 11 is returned to an overflow passage (not shown) via the pressure control valve 13. Changes the flow passage area of the overflow passage in accordance with the duty signal from the engine control unit 30. Thereby, the substantial fuel discharge amount from the supply pump 11 to the common rail 14 is adjusted, and the fuel pressure in the common rail 14 is controlled.

  The fuel injection valve 15 is an electronic injection valve that is opened and closed by an ON-OFF signal from the engine control unit 30, and injects fuel into the combustion chamber by the ON signal and stops injection by the OFF signal. The fuel injection amount increases as the period of the ON signal applied to the fuel injection valve 15 increases, and the fuel injection amount increases as the fuel pressure of the common rail 14 increases.

  A water temperature sensor 31 for detecting the cooling water temperature is attached to an appropriate position of the engine 1 as representative of the temperature of the internal combustion engine.

  The engine control unit 30 includes a signal from the water temperature sensor 31 (cooling water temperature Tw), a signal from the crank angle sensor 32 for crank angle detection (a crank angle signal serving as a basis for the engine speed Ne), and a crank angle sensor 33 for determining the cylinder. Signal (cylinder discrimination signal Cyl), a signal of the pressure sensor 34 for detecting the fuel pressure of the common rail 14 (common rail pressure Pcr), a signal of the temperature sensor 35 for detecting the fuel temperature (fuel temperature Tf), and an accelerator pedal corresponding to the load Accelerator opening sensor 40 signal (accelerator opening (load) Acc), air flow meter 7 signal (intake fresh air amount Gair), intake air temperature sensor 8 signal (intake air temperature Tair), pressure sensor 9 (intake pressure Pair), exhaust temperature sensors 36 and 37 (exhaust temperature T1) T2) are respectively input.

  Further, an exhaust pressure sensor 38 for detecting the exhaust pressure (Pdpf) and a DPF temperature sensor 39 for detecting the temperature (Tdpf) of the DPF 16 are provided on the DPF 16 inlet side of the exhaust passage 3, and these signals are also sent to the engine control unit 30. Have been entered.

  For example, a signal from a wheel rotation sensor (not shown) that detects the rotation of the wheel is input to the engine control unit 30, and the engine control unit 30 performs a vehicle travel distance based on this signal. Is accumulated and memorized.

  Based on these input signals, the engine control unit 30 controls the fuel injection command signal to the fuel injection valve 15 for controlling the injection amount and timing of fuel injection, the opening command signal to the intake throttle valve 6, and the EGR valve. An opening degree command signal to 5 is output.

  FIG. 3 is a basic control routine related to the control of the entire diesel engine 1.

  In S1000, intake fresh air amount Gair, intake air temperature Tair, intake air pressure Pair, water temperature Tw, engine speed Ne, cylinder discrimination signal Cyl, common rail pressure Pcr, fuel temperature Tf, accelerator opening Acc, exhaust temperatures T1, T2 , DPF pressure Pdf and DPF temperature Tdpf are read.

  In S2000, engine basic control is performed. In step S3000, the exhaust gas recirculation apparatus, which is a main part of the present invention, is controlled.

  FIG. 4 specifically shows S2000 of FIG. 3 and is a subroutine of engine basic control.

  In S2100, common rail pressure control is performed. The common rail pressure control itself is not the main part, so it will be described briefly. That is, the common rail pressure control calculates the target reference pressure PCR0 of the common rail 14 by searching a predetermined map stored in advance in the ROM of the engine control unit 30 using the engine speed Ne and the load Acc as parameters. Feedback control of the pressure control valve 13 is executed so that the target reference pressure PCR0 is obtained.

  In S2200, fuel injection timing control is performed. For example, using the engine speed Ne and the load Acc as parameters, the pilot injection amount Qpilot, the main fuel injection amount Qmain, the common rail pressure (injection pressure) PCR, the pilot injection period Pperiod, the main injection period Mperiod, the main injection start timing Mstart, and the pilot injection start The timing Pstart, the pilot injection interval DIT, and the like are obtained by searching predetermined map data stored in advance in the ROM of the engine control unit 30. Then, pilot injection is performed based on the crank angle signal of the crank angle sensor 32 for crank angle detection and the cylinder discrimination signal Cyl of the crank angle sensor 33 for cylinder discrimination so that the pilot injection amount Qpilot and the main fuel injection amount Qmain are supplied. The fuel injection valve 15 of the cylinder to be injected is driven to open during the period from the start timing Pstart to the period, and from the main injection start timing Mstart to the period Mperiod.

  In S2300, EGR control is performed. Here, it is first determined whether or not exhaust gas recirculation is necessary. Specifically, it is determined whether or not the engine speed Ne and the main fuel injection amount Qmain are within a predetermined EGR region set as parameters. That is, because the operation frequency is high and the excess air ratio is relatively large, even if exhaust gas recirculation is performed and NOx is reduced, other exhaust components and fuel consumption are not deteriorated, or the exhaust gas recirculation is performed. If it is performed, it is determined whether it is a region (outside the EGR region) where smoke or PM (exhaust particulate) emission increases or output decreases.

  In the EGR region, target EGR data (drive signals for the EGR valve 5 and the intake throttle valve 6) for executing appropriate exhaust gas recirculation, for example, using the engine speed Ne and the main fuel injection amount Qmain as parameters, A predetermined map stored in advance in the ROM of the engine control unit 30 is searched for and obtained. When the cooling water temperature Tw is low, the exhaust gas recirculation is corrected to decrease, and the EGR valve 5 and the intake throttle valve 6 are driven and controlled based on the corrected drive signals to perform the exhaust gas recirculation. If there is no need for exhaust gas recirculation outside the EGR region, the exhaust gas recirculation is stopped or stopped (the operation of the EGR valve 5 and the intake throttle valve 6 is stopped).

  In S2400, exhaust aftertreatment control is performed. For example, while monitoring the inlet pressure Pdpf of the DPF 16, the post-injection (a small amount of fuel injection performed after the main injection) or the like is performed at the regeneration timing to increase the DPF temperature Tdpf, and the PM trapped in the DPF 16 is removed by combustion. Alternatively, at the regeneration timing of the NOx trap catalyst, the intake throttle is strengthened (the intake throttle valve 6 is small), the exhaust gas recirculation is strengthened, or the post injection (a small amount of fuel is injected after the main injection) is used alone or in combination. By executing this, NOx regeneration is performed by enriching the air-fuel ratio of the exhaust gas discharged from the engine.

  FIG. 5 specifically shows S3000 of FIG. 3 and is a subroutine for controlling the exhaust gas recirculation device.

  In S3100, a control target value is set. In other words, this S3100 corresponds to the control target value setting means in FIG. 1, and the intake air target flow rate Vair, the EGR valve opening target value EGRdeg, the EGR cooler target heat release amount Qclr, and the cylinder intake gas target flow rate. Vcyl is calculated.

  In S3200, the intake air flow rate Vair1 is detected. In other words, this S3100 corresponds to the intake air flow rate detecting means in FIG.

  In S3300, the intake air flow rate reference value Vair0 is detected. In other words, this S3300 corresponds to a part of the intake air reference value detection means in FIG.

  In S3400, an abnormality diagnosis of the air flow meter 7 is performed. In other words, this S3400 corresponds to a part of the intake air reference value detection means in FIG.

  In S3500, abnormality diagnosis of the EGR system path and EGR valve opening correction are performed. In other words, S3500 corresponds to the EGR path diagnosis unit and the EGR valve opening target value setting unit in FIG.

  In S3600, the heat release amount of the EGR cooler 17 is detected. In other words, this S3600 corresponds to the EGR cooler heat radiation amount detection means in FIG.

  In S3700, abnormality diagnosis and control target value correction of the EGR cooler 17 are performed. In other words, this S3700 corresponds to the EGR cooler diagnosis means, the intake air target flow rate setting means, and the EGR cooler target heat release amount setting means in FIG.

  In S3800, warning control is performed.

  FIG. 6 specifically shows S3100 of FIG. 5 and is a control target value setting subroutine.

  In S3110 to S3140, the intake air target flow rate Vair, the EGR valve opening target value EGRdeg (or the opening signal), the cylinder intake gas target flow rate Vcyl, and the target heat release amount of the EGR cooler 17 using the engine speed Ne and the load Acc as parameters. Qclr is obtained by searching predetermined map data stored in advance in the ROM of the engine control unit 30.

  Further, the intake air target flow rate Vair, the EGR valve opening target value EGRdeg, and the EGR cooler target heat release amount Qclr, respectively, will be described later as an intake air target flow rate correction coefficient KVair, an EGR valve opening target value correction coefficient KEGRdeg, and EGR, respectively. It corrects with the cooler target heat radiation correction coefficient KQclr.

  S3110 corresponds to the intake air target flow rate setting means in FIG. 1, S3120 corresponds to the EGR valve opening target value setting means in FIG. 1, and S3130 corresponds to the cylinder intake gas target flow rate setting means in FIG. S3140 corresponds to the EGR cooler target heat radiation amount setting means in FIG.

  FIG. 7 specifically shows S3200 of FIG. 5 and is a subroutine for detecting the intake air flow rate.

In this subroutine for detecting the intake air flow rate, the intake air flow rate Vair1 is calculated using Equation (1) and Equation (2). In addition, P0 and T0 in Formula (1) are the pressure and temperature in a standard state, and are set to P0 = 1bar (100kPa) and T0 = 25 degreeC (298.16K).
(Equation 1)
γair = γ0 × (Pair / P0) × (T0 / Tair) (1)
(Equation 2)
Vair1 = Gair / γair (2)
More specifically, in S3210, the specific gravity γair of the actual intake air is calculated from the above-described equation (1) using the temperature Tair and the pressure Pair.

  In S3220, the intake air flow rate Vair1 is calculated from the above-described equation (2) using the intake fresh air amount Gair detected by the air flow meter 7 and the air specific gravity γair.

  FIG. 8 specifically shows S3300 of FIG. 5 and is a subroutine for detecting an intake air flow rate reference value.

  In S3310, it is determined whether or not the current total travel distance Run stored in the engine control unit 30 is less than a predetermined value Run1. If the total travel distance Run is smaller than the predetermined value Run1, Proceeding to S3320, if the total travel distance Run is greater than or equal to the predetermined value Run1, the current routine is terminated. For example, a value of about 2000 to 5000 km is set as the predetermined value Run1.

  In S3320, it is determined whether or not the operation condition is in the EGR stop area, and if the operation condition is in the EGR stop area, the process proceeds to S3330, and the operation condition is not in the EGR stop area. This routine ends.

  In S3330, an error Deff of the intake air flow rate Vair1 with respect to the currently set intake air flow rate reference value Vair0 is calculated. At the time of shipment from the factory, an initial value of the intake air flow rate reference value Vair0 is set.

  In S3340, the error Deff is compared with a preset predetermined value Deff1, and if the error Deff is greater than or equal to the predetermined value Deff1, the process proceeds to S3360, and the value of the intake air flow rate reference value Vair0 is set to the current value of the intake air flow rate Vair1. rewrite.

  On the other hand, if the error Deff is smaller than the predetermined value Deff1, the process proceeds to S3350, and the intake air flow rate reference value Vair0 is not rewritten.

  FIG. 9 specifically shows S3400 of FIG. 5 and is an air flow meter abnormality diagnosis subroutine.

  In S3410, it is determined whether or not the current total travel distance Run stored in the engine control unit 30 is less than a predetermined value Run1, and if the total travel distance Run is smaller than the predetermined value Run1. Proceeding to S3420, if the total travel distance Run is greater than or equal to the predetermined value Run1, the current routine is terminated.

  In S3420, it is determined whether or not the operation condition is in the EGR stop area, and if the operation condition is in the EGR stop area, the process proceeds to S3430, and the operation condition is not in the EGR stop area. This routine ends.

  In S3430, a deviation Vadlt of the intake air flow rate Vair1 with respect to the currently set intake air flow rate reference value Vair0 is calculated.

  In S3440, the deviation Vadlt is compared with a predetermined deviation Vadlt1, and if the deviation Vadlt is equal to or larger than the predetermined deviation Vadlt1, the process proceeds to S3460, and the air flow meter 7 is diagnosed as having an abnormality (or an abnormality in the intake passage).

  On the other hand, when the deviation Vadlt is smaller than the predetermined deviation Vadlt1, the process proceeds to S3450 and it is diagnosed that there is no abnormality in the air flow meter 7.

  FIG. 10 specifically shows S3500 of FIG. 5, and is a subroutine for EGR system path abnormality diagnosis and EGR valve opening correction.

  In S3510, it is determined whether the operation condition is in the EGR operation area, that is, whether the operation condition is in the EGR operation area. If the operation condition is in the EGR operation area, the process proceeds to S3520, and the operation condition is not in the EGR operation area. This routine ends.

  In S3520, a deviation Vdelta of the intake air flow rate Vair1 with respect to the current intake air target flow rate Vair is calculated.

  In S3530, the deviation Vdelta is compared with a predetermined deviation Vdelta1 as a preset intake air flow rate deviation. If the deviation Vdelta is equal to or larger than the predetermined deviation Vdelta1, the process proceeds to S3550, and the EGR system path is abnormal (clogged or EGR blocked). Diagnose that the valve opening is abnormal).

  On the other hand, if the deviation Vdelta is smaller than the predetermined deviation Vdelta1, the process proceeds to S3540 and a diagnosis is made that there is no abnormality in the EGR system path.

  When it is diagnosed that there is an abnormality in the EGR system path, in S3550, the EGR valve opening target value correction coefficient KEGRdeg is calculated from, for example, table data in accordance with the deviation Vdelta. The EGR valve opening target value correction coefficient KEGRdeg becomes larger when the intake air flow rate Vair1 is larger than the intake air target flow rate Vair (when the EGR flow rate decreases and the intake air flow rate Vair1 increases due to clogging of the EGR passage 4). Conversely, when the intake air flow rate Vair1 is smaller than the intake air target flow rate Vair (when the EGR passage 4 is open), it is set to be small. Then, EGR is adjusted to the target value as the EGR route recovery procedure. When it is diagnosed that there is no abnormality in the EGR system path (when the deviation Vadlt is smaller than the predetermined deviation Vadlt1), the EGR valve opening target value correction coefficient KEGRdeg is not changed. The initial value of the EGR valve opening target value correction coefficient KEGRdeg is set to 1.

  FIG. 11 specifically shows S3600 of FIG. 5, and is a subroutine for detecting the amount of heat released from the EGR cooler.

In S3610, EGR volume flow rate Vegr1 is calculated using equation (3).
(Equation 3)
Vegr1 = Vcyl-Vair1 (3)
That is, the EGR volume flow rate Vegr1 is calculated by subtracting the intake air flow rate Vair1 from the cylinder intake gas target flow rate Vcyl.

  In S3620, the exhaust specific gravity γegr determined by the operating conditions is determined from the map data.

In S3630, EGR mass flow rate Gegr1 is calculated using equation (4).
(Equation 4)
Gegr1 = Vegr1 × γegr (4)
That is, the EGR mass flow rate Gegr1 is calculated by multiplying the EGR volume flow rate Vegr1 calculated in S3610 by the exhaust specific gravity γegr obtained in S3620.

In S3640, the EGR cooler heat dissipation amount Qclr1 is calculated using Expression (5).
(Equation 5)
Qclr1 = Gegr1 * Cp * (T1-T2) (5)
That is, the heat release amount Qclr1 of the EGR cooler 17 is obtained from the EGR mass flow rate Gegr1 and the gas temperatures (T1, T2) before and after the EGR cooler 17. Here, Cp is an exhaust gas specific heat (J / kg · K) set in advance corresponding to the EGR volume flow rate Vegr1 and the exhaust specific gravity γegr.

  FIG. 12 specifically shows S3700 of FIG. 5, and is a subroutine for EGR cooler abnormality diagnosis and control target value correction.

  In S3710, it is determined whether the operation condition is in the EGR operation area, that is, whether the operation condition is in the EGR operation area. If the operation condition is in the EGR operation area, the process proceeds to S3720, and the operation condition is not in the EGR operation area. This routine ends.

  In S3720, a deviation Qdelta of the EGR cooler heat release amount Qclr1 with respect to the current EGR cooler target heat release amount Qclr is calculated.

  In S3730, the deviation Qdelta is compared with a predetermined deviation Qdelta1 as a preset heat dissipation amount deviation. If the deviation Qdelta is equal to or larger than the predetermined deviation Qdelta1, the process proceeds to S3750, and the EGR cooler 17 is abnormal (cooling by covering or depositing soot). Diagnose that there is an abnormality due to efficiency reduction)

  On the other hand, when the deviation Qdelta is smaller than the predetermined deviation Qdelta1, the process proceeds to S3740 and it is diagnosed that the EGR cooler 17 is normal.

  If it is diagnosed that the EGR cooler 17 is abnormal, in S3750, the intake air target flow rate correction coefficient KVair and the EGR cooler target heat release amount correction coefficient KQclr are calculated from, for example, table data in accordance with the deviation Qdelta.

  The intake air target flow rate correction coefficient KVair and the EGR cooler target heat dissipation amount correction coefficient KQclr are calculated in order to match the intake air target flow rate Vair and the EGR cooler target heat dissipation amount Qclr to, for example, the EGR rate. The EGR rate is kept constant by increasing the EGR volume flow rate Vegr and decreasing the intake air flow rate Vair1. For this reason, the EGR cooler target heat dissipation amount Qclr is also corrected to meet this requirement. More specifically, when the EGR cooler heat release amount Qclr1 is smaller than the EGR cooler target heat release amount Qclr (when the heat release amount decreases due to carbon deposition, and therefore the EGR mass flow rate Gegr1 decreases), the EGR rate is adjusted to the target value. Therefore, by increasing the EGR volume flow rate Vegr1 and decreasing the intake air flow rate Vair1, the intake air target flow rate correction coefficient KVair is decreased in order to keep the EGR rate constant, and the EGR cooler target heat dissipation amount Qclr is set accordingly. The EGR cooler target heat radiation correction coefficient KQclr is increased so as to increase. The initial values of the intake air target flow rate correction coefficient KVair and the EGR cooler target heat radiation amount correction coefficient KQclr are set to 1, respectively.

  FIG. 13 specifically shows S3800 of FIG. 5 and is a warning control subroutine.

  In response to an abnormality in the air flow meter 7 that is a key part of the control, for example, a warning light for monitoring is turned on to prompt repair and inspection.

  More specifically, in S3810, it is determined whether or not there is an abnormality in the air flow meter 7. If there is an abnormality, the process proceeds to S3830 and the air flow meter abnormality warning light is turned on. If there is no abnormality, the process proceeds to S3820 and the air flow meter abnormality warning light is turned off.

  In the first embodiment, since the abnormality diagnosis of the air flow meter 7, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler 17 can be separately performed, the performance deterioration of the air flow meter 7 (or the intake system) Leakage), EGR system troubles (clogging due to system defects, deterioration of EGR valve opening control accuracy), and cooling capacity decrease due to EGR cooler 17 being covered with soot. Therefore, the control accuracy related to the entire EGR system can be improved.

  Of course, since the cooling capacity decrease due to the EGR cooler 17 being covered with the soot can be diagnosed, the control accuracy of the EGR can be improved according to each diagnosis result or the situation, and the exhaust emission level can be stabilized.

  When the amount of heat released from the EGR cooler 17 has not decreased, the EGR valve opening degree control is performed in accordance with the detected deviation Vdelta between the intake air flow rate Vair1 and the intake air target flow rate Vair, thereby causing an EGR path abnormality. It is possible to improve the control accuracy of the EGR rate at the time (clogging due to soot or deviation from the target value of the EGR valve opening).

  Further, when the cooling efficiency (heat radiation amount) of the EGR cooler 17 is lowered, the exhaust performance can be prevented from deteriorating by correcting and controlling the intake air target flow rate Vair and the EGR cooler target heat dissipation amount Qclr. . This can be realized, for example, by keeping the EGR rate constant and not increasing the NOx emission amount as shown in FIG.

  Next, a second embodiment of the present invention will be described. In addition, about the same component as 1st Embodiment mentioned above, the same code | symbol is attached and the overlapping description is abbreviate | omitted.

  FIG. 14 shows a system configuration diagram of a diesel engine provided with an exhaust gas recirculation control apparatus according to a second embodiment of the present invention, and the diesel engine uses light oil as fuel. FIG. 15 also corresponds to a block diagram of the exhaust gas recirculation control apparatus according to the second embodiment of the present invention.

  The second embodiment has substantially the same configuration as the first embodiment described above. However, in the second embodiment, the water amount adjusting means of the EGR cooler 17 is added to the first embodiment described above. Configured. That is, as shown in FIG. 14, the EGR cooler 17 is configured by adding a water amount adjusting valve 18 that is controlled to be opened and closed by the control unit 30. The water amount adjusting means corresponds to the EGR cooler control means in FIG. In addition, a cooling water system having a water temperature adjusting means such as a water amount adjusting valve or an electric fan may be separately provided for the EGR cooler 17 to adjust the water amount or the water temperature.

  This second embodiment is controlled in substantially the same manner as the first embodiment described above, but since the water amount adjustment valve 18 is added to the EGR cooler 17, it is necessary to correct the target heat release amount Qclr of the EGR cooler 17. Disappear. That is, the control target value setting subroutine in the second embodiment is the same as the control target value setting subroutine in the first embodiment (see FIG. 6) from S3110 to S3130 as shown in FIG. S3150 for calculating the target heat release amount Qclr of the EGR cooler 17 is different from S3140 of the control target value setting subroutine in the first embodiment.

  Further, the subroutine for EGR cooler abnormality diagnosis and control target value correction in the second embodiment has substantially the same configuration as the subroutine for EGR cooler abnormality diagnosis and control target value correction in the first embodiment described above, but in S3730 If the deviation Qdelta is equal to or greater than the predetermined deviation Qdelta1, the process proceeds to S3760, and a recovery process for the cooling efficiency (heat radiation amount) of the EGR cooler 17 is performed. That is, the valve opening degree of the water amount adjusting valve 18 is controlled so that the cooling efficiency (heat radiation amount) of the EGR cooler 17 is recovered. In S3760, the intake air target flow rate correction coefficient KVair is calculated according to the deviation Qdelta.

  In such a second embodiment, when the cooling efficiency (heat radiation amount) of the EGR cooler 17 is lowered, the quality (rate, amount) of EGR can be obtained by performing a recovery process of the cooling efficiency (heat radiation amount). , Temperature) can be prevented from fluctuating, and fluctuations in exhaust performance can be prevented.

  In the second embodiment, similarly to the first embodiment described above, the abnormality diagnosis of the air flow meter 7, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler 17 can be performed separately. The control accuracy relating to the entire system can be improved. Further, since the cooling capacity decrease due to the EGR cooler 17 being covered with the soot can be diagnosed, the control accuracy of the EGR can be improved according to each diagnosis result or the situation, and the exhaust emission level can be stabilized.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) The exhaust gas recirculation control device for an internal combustion engine, as shown in FIG. 1, operates condition detecting means for detecting an operating condition of the internal combustion engine, and recirculates a part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system. Applied to an internal combustion engine provided with an EGR passage, an EGR valve provided in the middle of the EGR passage, and an EGR cooler for cooling EGR gas, and at least a volumetric flow rate according to the operating condition detected by the operating condition detecting means Control target value setting means for setting an intake air target flow rate (Vair), an EGR valve opening target value (EGRdeg), an EGR cooler target heat release amount (Qclr), and a cylinder intake gas target flow rate (Vcyl) that is a volume flow rate; , An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) which is a volume flow rate, at least a detected operating condition and a detected intake air flow rate (V The intake air flow rate reference value (Vair0), which is a volume flow rate, is detected from ir1), and an abnormality diagnosis of the intake air flow rate detection means is performed using the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0). The EGR cooler heat release amount (Qclr1) is detected from the intake air reference value detection means, the detected operating condition, the detected intake air flow rate (Vair1), and the control target value set by the control target value setting means. EGR cooler heat release amount detection means, EGR path diagnosis means for diagnosing EGR path abnormality from the detected intake air flow rate (Vair1), and a control target value set by the control target value setting means are detected. EGR cooler diagnosis means for diagnosing EGR cooler abnormality based on the EGR cooler heat dissipation amount (Qclr1), and EGR path diagnosis Has a diagnosis result means, and diagnosis of the EGR cooler diagnostic means, based on the set control target value by the target control value setting means, and EGR control means for opening and closing control of the EGR valve, the.

  Accordingly, the abnormality diagnosis of the intake air flow rate detection means, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler (decrease in cooling capacity) can be performed separately. For this reason, it is possible to diagnose performance deterioration of the intake air flow rate detection means (or leakage from the intake system) and troubles in the EGR system (clogging due to system fouling, deterioration in EGR valve opening control accuracy). Of course, since the cooling capacity decrease due to the EGR cooler being covered with the soot can be diagnosed, the control accuracy of the EGR can be improved according to each diagnosis result or the situation, and the exhaust emission level can be stabilized.

  (2) In the exhaust gas recirculation control device for an internal combustion engine according to (1), the intake air flow rate detection means includes intake fresh air amount detection means for detecting an intake fresh air amount (Gair) of the internal combustion engine, and intake fresh air. Intake fresh air temperature detection means for detecting the temperature and intake fresh air pressure detection means for detecting the intake fresh air pressure, and the detected intake fresh air amount (Gair), the intake fresh air temperature, and the intake fresh air pressure. An intake air flow rate calculation means for calculating the intake air flow rate (Vair1) based on this is provided.

  (3) In the exhaust gas recirculation control device for an internal combustion engine according to (1) or (2), the intake air reference value detection means detects vehicle travel distance that detects the total travel distance (Run) from the new vehicle state of the vehicle. And when the detected total travel distance (Run) is less than or equal to a predetermined value (Run1), based on the detected operating condition and the detected intake air flow rate (Vair1), The intake air flow rate reference value (Vair0) is learned and set, and when the travel distance exceeds the predetermined value (Run1), it is detected with respect to the currently set intake air flow rate reference value (Vair0). If the deviation (Vadlt) of the intake air flow rate (Vair1) is equal to or less than the predetermined deviation (Vadlt1), there is no abnormality in the intake air flow rate detection means, and if the deviation (Vadlt1) is equal to or greater than the predetermined deviation (Vadlt1). Having an intake air reference value setting diagnosing means diagnoses that there is an abnormality in the input air flow rate detecting means.

  (4) In the exhaust gas recirculation control apparatus for an internal combustion engine according to any one of (1) to (3), the EGR cooler heat release amount detection means is a cylinder intake gas target flow rate (Vcyl) set by the control target value setting means. ) And the detected intake air flow rate (Vair1), the EGR volume flow rate (Vegr1) is calculated, and the EGR mass flow rate is calculated based on the specific gravity of the exhaust gas determined in advance by the operating conditions and the calculated EGR volume flow rate (Vegr1). EGR flow rate calculating means for calculating (Gegr1), EGR cooler front and rear exhaust temperature detecting means for detecting the EGR gas temperature before and after the EGR cooler, the calculated EGR mass flow rate (Gegr1) and the detected exhaust gas temperature before and after the EGR cooler EGR cooler heat dissipation amount calculation means for calculating an EGR cooler heat dissipation amount (Qclr1).

  (5) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (4), the EGR path diagnosis means detects an intake air target flow rate (Vair) determined by operating conditions. If the deviation (Vdelta) of the measured intake air flow rate (Vair1) is equal to or less than the allowable intake air flow rate deviation (Vdelta1), it is diagnosed that there is no abnormality in the EGR system path, and if it is equal to or greater than the intake air flow rate deviation (Vdelta1). The EGR system is diagnosed as having an abnormality in the EGR system, and the EGR control means performs a recovery process of the intake air flow rate according to the detected intake air flow rate (Vair1) when the EGR system is diagnosed as having an abnormality.

  (6) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (5), the EGR valve target opening (EGRdeg) is set to an intake air target flow rate (Vair) determined by operating conditions. Correction is performed according to the deviation (Vdelta) from the detected intake air flow rate (Vair1).

  (7) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (6) above, the EGR cooler diagnosis unit is configured to perform an EGR cooler target heat release amount (Qclr) determined by operating conditions. If the detected EGR cooler heat release amount (Qclr1) deviation is equal to or less than the allowable heat release amount deviation (Qdelta1), it is diagnosed that there is no abnormality in the cooling efficiency of the EGR cooler, and the release is released. If it is equal to or greater than the calorific value deviation (Qdelta1), it is diagnosed that the cooling efficiency of the EGR cooler is abnormal, and if the EGR control means is diagnosed as abnormal in the cooling efficiency of the EGR cooler, the intake air target flow rate (Vair) and EGR The cooler target heat dissipation amount (Qclr) is corrected according to the EGR cooler heat dissipation amount deviation (Qdelta).

  (8) The exhaust gas recirculation control device for an internal combustion engine, as shown in FIG. 15, returns an operating condition detection means for detecting the operating condition of the internal combustion engine and a part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system. Applied to an internal combustion engine provided with an EGR passage, an EGR valve provided in the middle of the EGR passage, and an EGR cooler for cooling EGR gas, and at least a volumetric flow rate according to the operating condition detected by the operating condition detecting means Control target value setting means for setting an intake air target flow rate (Vair), an EGR valve target opening (EGRdeg), an EGR cooler target heat release amount (Qclr), and a cylinder intake gas target flow rate (Vcyl) that is a volume flow rate; An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) which is a volume flow rate, at least a detected operating condition, and a detected intake air flow rate (V The intake air flow rate reference value (Vair0), which is a volume flow rate, is detected from ir1), and an abnormality diagnosis of the intake air flow rate detection means is performed using the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0). EGR for detecting the heat release amount of the EGR cooler from the intake air reference value detection means, the detected operating condition, the detected intake air flow rate (Vair1), and the control target value set by the control target value setting means It is set by a cooler heat release amount detection means, an EGR path diagnosis means for diagnosing an EGR path abnormality from the detected intake air flow rate (Vair1), a diagnosis result of the EGR path diagnosis means, and a control target value setting means EGR control means for performing opening / closing control of the EGR valve based on the control target value, a control target value set by the control target value setting means, and EG EGR cooler diagnosis means for diagnosing an EGR cooler abnormality based on the EGR cooler heat release amount (Qclr1) detected by the R cooler heat release amount detection means, and cooling efficiency control of the EGR cooler based on the diagnosis result of the EGR cooler diagnosis means EGR cooler control means for performing

  Accordingly, the abnormality diagnosis of the intake air flow rate detection means, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler (decrease in cooling capacity) can be performed separately. For this reason, it is possible to diagnose performance deterioration of the intake air flow rate detection means (or leakage from the intake system) and troubles in the EGR system (clogging due to system fouling, deterioration in EGR valve opening control accuracy). Of course, since the cooling capacity decrease due to the EGR cooler being covered with the soot can be diagnosed, the control accuracy of the EGR can be improved according to each diagnosis result or the situation, and the exhaust emission level can be stabilized.

  (9) In the exhaust gas recirculation control apparatus for an internal combustion engine according to (8), the EGR cooler control means detects EGR detected when the EGR cooler diagnosis means diagnoses that the cooling efficiency of the EGR cooler is abnormal. The EGR cooler heat dissipation amount is recovered according to the cooler heat dissipation amount (Qclr1).

  As a result, the quality (rate, quantity, temperature) of EGR can be prevented from fluctuating, and fluctuations in exhaust performance can be prevented.

1 is a block diagram illustrating an exhaust gas recirculation control device for an internal combustion engine according to a first embodiment of the present invention. The system block diagram of the diesel engine provided with the exhaust gas recirculation | reflux control apparatus in 1st Embodiment of this invention. The flowchart which shows the basic control routine of a diesel engine. The flowchart which shows the subroutine of engine basic control. The flowchart which shows the subroutine of exhaust gas recirculation | reflux apparatus control. The flowchart which shows the subroutine of control target value setting. The flowchart which shows the subroutine of an intake air flow rate detection. The flowchart which shows the subroutine of an intake air flow rate reference value detection. The flowchart which shows the subroutine of an airflow meter abnormality diagnosis. The flowchart which shows the subroutine of EGR system line abnormality diagnosis and EGR valve opening correction | amendment. The flowchart which shows the subroutine of EGR cooler thermal radiation amount detection. The flowchart which shows the subroutine of EGR cooler abnormality diagnosis and control target value correction | amendment. The flowchart which shows the subroutine of warning control. The system block diagram of the diesel engine provided with the exhaust gas recirculation | reflux control apparatus in 2nd Embodiment of this invention. The block diagram showing the exhaust gas recirculation control apparatus of the internal combustion engine in 2nd Embodiment of this invention. The flowchart which shows the control target value setting subroutine in 2nd Embodiment of this invention. The flowchart which shows the subroutine of EGR cooler abnormality diagnosis and control target value correction | amendment in 2nd Embodiment of this invention. The characteristic diagram which showed the correlation of the EGR rate and NOx discharge | emission amount of three EGR coolers of the same type from which cooling capacity changed with time. The characteristic diagram which showed the cooling capacity of the three EGR coolers of the same type from which the cooling capacity changed with time. The characteristic diagram which showed the volumetric flow volume of EGR which passes three EGR coolers of the same form from which cooling capacity changed with time change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 4 ... EGR channel | path 7 ... Air flow meter 10 ... Fuel-injection apparatus 17 ... EGR cooler 30 ... Engine control unit

Claims (9)

An operating condition detecting means for detecting an operating condition of the internal combustion engine, an EGR passage for returning a part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system, an EGR valve provided in the middle of the EGR passage, and EGR gas In an internal combustion engine provided with an EGR cooler for cooling,
According to the operating conditions detected by the operating condition detecting means, at least the intake air target flow rate (Vair), which is a volume flow rate, the EGR valve opening target value (EGRdeg), the EGR cooler target heat release amount (Qclr), and the volume flow rate. Control target value setting means for setting a cylinder intake gas target flow rate (Vcyl);
An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) which is a volume flow rate;
An intake air flow rate reference value (Vair0), which is a volumetric flow rate, is detected from at least the detected operating conditions and the detected intake air flow rate (Vair1), and the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0). An intake air reference value detecting means for performing an abnormality diagnosis of the intake air flow rate detecting means using
EGR cooler heat release amount detection means for detecting an EGR cooler heat release amount (Qclr1) from the detected operating condition, the detected intake air flow rate (Vair1), and the control target value set by the control target value setting means; ,
EGR path diagnosis means for diagnosing an abnormality of the EGR path from the detected intake air flow rate (Vair1);
EGR cooler diagnostic means for diagnosing an abnormality of the EGR cooler based on the control target value set by the control target value setting means and the detected EGR cooler heat release amount (Qclr1);
EGR control means for performing opening / closing control of the EGR valve based on the diagnosis result of the EGR system path diagnosis means, the diagnosis result of the EGR cooler diagnosis means, and the control target value set by the control target value setting means An exhaust gas recirculation control device for an internal combustion engine.   The intake air flow rate detection means detects the intake fresh air amount detection means for detecting the intake fresh air quantity (Gair) of the internal combustion engine, the intake fresh air temperature detection means for detecting the intake fresh air temperature, and detects the intake fresh air pressure. In addition to the intake fresh air pressure detection means, intake air flow rate calculation means for calculating the intake air flow rate (Vair1) based on the detected intake fresh air amount (Gair), the intake fresh air temperature, and the intake fresh air pressure. 2. The exhaust gas recirculation control apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation control apparatus is configured.   The intake air reference value detection means has vehicle travel distance detection means for detecting the total travel distance (Run) from the new vehicle state of the vehicle, and the detected total travel distance (Run) is less than or equal to a predetermined value (Run1) In addition, based on the detected operating condition and the detected intake air flow rate (Vair1), the intake air flow rate reference value (Vair0) is learned and set under the predetermined operating condition, and the travel distance is set to the predetermined value ( If the deviation (Vadlt) of the detected intake air flow rate (Vair1) with respect to the currently set intake air flow rate reference value (Vair0) is less than a predetermined deviation (Vadlt1) There is an intake air reference value setting diagnosis means for diagnosing that there is an abnormality in the intake air flow rate detection means if there is no abnormality in the intake air flow rate detection means and a predetermined deviation (Vadlt1) or more. Exhaust gas recirculation control apparatus for an internal combustion engine according to claim 1 or 2, characterized in that. The EGR cooler heat release amount detection means calculates the EGR volume flow rate (Vegr1) based on the cylinder intake gas target flow rate (Vcyl) set by the control target value setting means and the detected intake air flow rate (Vair1), and in advance. EGR flow rate calculation means for calculating the EGR mass flow rate (Gegr1) based on the specific gravity of the exhaust gas determined by the operating conditions and the calculated EGR volumetric flow rate (Vegr1); EGR cooler front-rear exhaust gas for detecting the EGR gas temperature before and after the EGR cooler A temperature detection means, and an EGR cooler heat release amount calculation means for calculating an EGR cooler heat release amount (Qclr1) from the calculated EGR mass flow rate (Gegr1) and the detected exhaust temperature before and after the EGR cooler. Item 4. An exhaust gas recirculation control device for an internal combustion engine according to any one of Items 1 to 3. The EGR path diagnosis means has an intake air flow rate deviation (Vdelta1) equal to or smaller than an allowable intake air flow rate deviation (Vdelta1) with respect to the detected intake air flow rate (Vair1) with respect to the intake air target flow rate (Vair) determined by operating conditions. If there is an abnormality in the EGR path, it is diagnosed that there is an abnormality in the intake air flow rate deviation (Vdelta1).
The EGR control means performs recovery processing of the intake air flow rate according to the detected intake air flow rate (Vair1) when it is diagnosed that there is an abnormality in the EGR system path. 2. An exhaust gas recirculation control device for an internal combustion engine according to 1.   The EGR valve target opening (EGRdeg) is corrected in accordance with a deviation (Vdelta) between the intake air target flow rate (Vair) determined by operating conditions and the detected intake air flow rate (Vair1). Item 6. An exhaust gas recirculation control device for an internal combustion engine according to any one of Items 1 to 5. The EGR cooler diagnosis means allows an EGR cooler heat dissipation amount deviation (Qdelta) that is a deviation of the detected EGR cooler heat dissipation amount (Qclr1) with respect to the EGR cooler target heat dissipation amount (Qclr) determined by operating conditions. If it is less than the heat dissipation deviation (Qdelta1), it is diagnosed that there is no abnormality in the cooling efficiency of the EGR cooler, and if it is more than the heat dissipation deviation (Qdelta1), it is diagnosed that the cooling efficiency of the EGR cooler is abnormal,
When it is diagnosed that the cooling efficiency of the EGR cooler is abnormal, the EGR control means corrects the intake air target flow rate (Vair) and the EGR cooler target heat release amount (Qclr) according to the EGR cooler heat release amount deviation (Qdelta). The exhaust gas recirculation control apparatus for an internal combustion engine according to any one of claims 1 to 6. An operating condition detecting means for detecting an operating condition of the internal combustion engine, an EGR passage for returning a part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system, an EGR valve provided in the middle of the EGR passage, and EGR gas In an internal combustion engine provided with an EGR cooler for cooling,
In accordance with the operating conditions detected by the operating condition detecting means, at least the intake air target flow rate (Vair), which is a volume flow rate, the EGR valve target opening (EGRdeg), the EGR cooler target heat release amount (Qclr), and the cylinder, which is a volume flow rate Control target value setting means for setting a suction gas target flow rate (Vcyl);
An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) which is a volume flow rate;
An intake air flow rate reference value (Vair0), which is a volumetric flow rate, is detected from at least the detected operating conditions and the detected intake air flow rate (Vair1), and the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0). An intake air reference value detecting means for performing an abnormality diagnosis of the intake air flow rate detecting means using
EGR cooler heat release amount detection means for detecting the heat release amount of the EGR cooler from the detected operating condition, the detected intake air flow rate (Vair1), and the control target value set by the control target value setting means;
EGR path diagnosis means for diagnosing an abnormality of the EGR path from the detected intake air flow rate (Vair1);
EGR control means for performing opening / closing control of the EGR valve based on the diagnosis result of the EGR system path diagnosis means and the control target value set by the control target value setting means,
EGR cooler diagnostic means for diagnosing abnormality of the EGR cooler based on the control target value set by the control target value setting means and the EGR cooler heat release amount (Qclr1) detected by the EGR cooler heat release amount detection means;
An exhaust gas recirculation control device for an internal combustion engine, comprising: EGR cooler control means for controlling cooling efficiency of the EGR cooler based on a diagnosis result of the EGR cooler diagnosis means.   The EGR cooler control means performs an EGR cooler heat dissipation recovery process according to the detected EGR cooler heat dissipation (Qclr1) when the EGR cooler diagnosis means diagnoses that there is an abnormality in the cooling efficiency of the EGR cooler. The exhaust gas recirculation control apparatus for an internal combustion engine according to claim 8.

Images