JP2009114871A - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve control accuracy of EGR system. <P>SOLUTION: An exhaust gas recirculation control device includes a means detecting cetane number; a means setting control target value according to the cetane number; a means detecting intake air flow rate; a means diagnosing abnormality of the intake air flow rate detection means from an operation condition and intake air flow rate; a means detecting EGR cooler heat radiation quantity from the operation condition, intake air flow rate, and the control target value; an EGR route diagnosis means diagnosing abnormality of an EGR route from the intake air flow rate, a means controlling open and close of the an EGR valve from a diagnosis result of the EGR route diagnosis means and the control target value; an EGR cooler diagnosis means diagnosing cooling efficiency of an EGR cooler from the control target value, the EGR cooler radiation heat quantity, and the diagnosis result of the EGR route diagnosis means; and an EGR cooler control means controlling cooling efficiency of the EGR cooler from a diagnosis result of the EGR cooler diagnosis means. <P>COPYRIGHT: (C)2009,JPO&INPIT

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.

  The present invention

  Patent Document 1 has an ignition timing detection means using an in-cylinder pressure sensor, and when the target ignition timing and the actual ignition timing differ due to variations in the cetane number of the fuel in the market, the ignition timing is the target ignition timing. Thus, the technique regarding the combustion control of the diesel engine which changes injection timing, an EGR rate, etc. is disclosed.

In Patent Document 2, an EGR device including an actuator for adjusting an EGR amount and an EGR cooler is a diagnosis target, and an EGR amount, an intake fresh air state amount, an exhaust exhaust state amount are determined based on a detection value of an air flow meter. Actuate the actuator 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 is zero. A technique for diagnosing the presence or absence of an abnormality in the EGR cooler based on a comparison between the manipulated variable and the reference value is disclosed.
Japanese Patent Laid-Open No. 11-107820 Japanese Patent Laid-Open No. 2006-242080

  As shown in FIG. 19, when a fuel having a low cetane number is used, the interval from when the fuel is injected to when the fuel is ignited is widened, and the premixing of the injected fuel is promoted after the ignition timing is delayed. As a result, the premixed combustion ratio is increased, and a sudden heat generation is caused to increase the combustion noise and the NOx emission amount. Conversely, when a fuel with a high cetane number is used, the interval from when the fuel is injected to when it is ignited narrows and the ignition timing is advanced, so that the premixing of the injected fuel is suppressed and the diffusion combustion ratio is increased. Rise. As a result, the heat generation becomes slow, so that the combustion noise is reduced but the smoke emission amount is increased.

  When the ignition timing is adjusted by changing the injection timing as in Patent Document 1, the injection timing is advanced when a low cetane number fuel is used, and the injection is performed when a high cetane number fuel is used. Although it is necessary to delay the timing, the premixed combustion ratio and the diffusion combustion ratio cannot be matched, and there is a problem that fluctuations in combustion noise, NOx, and smoke emissions cannot be eliminated.

  Even when the ignition timing is adjusted by changing the EGR rate, the EGR rate is decreased when a low cetane number fuel is used, and the EGR rate is increased when a high cetane number fuel is used. There is a need. However, when EGR is reduced, NOx emissions will increase. Conversely, when the EGR rate is increased, the oxygen concentration in the working gas decreases (inert gas concentration increases) and combustion slows down. Therefore, there is a problem that although the NOx is reduced, the smoke emission amount is increased.

  On the other hand, in Patent Document 2, 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. 20, the intake air flow rate is the EGR cooler. However, there is a problem in that the decrease in EGR due to the decrease in the 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 abnormality diagnosis is performed based on the control amount. However, as shown in FIG. 21 and FIG. Volume flow does not change.

  That is, in three EGR coolers of the same type whose cooling capacity has changed due to changes over time, as shown in FIG. 21, the temperature drop (delta Temp) of 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 the three EGR coolers of the same type whose cooling capacity has changed due to changes over time. Therefore, as shown in FIG. 22, 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. 20, FIG. 21 and FIG. 22 is a characteristic line of an EGR cooler having a normal cooling capacity, that is, a cooling capacity that has not deteriorated 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. An EGR passage returning to the EGR passage, an EGR valve provided in the middle of the EGR passage, an EGR cooler for cooling the EGR gas, a fuel property detecting means for detecting at least a cetane number among the properties of the fuel used, In the internal combustion engine provided with the engine, the intake air target flow rate (Vair), which is a volume flow rate, and the EGR valve according to the operation condition detected by the operation condition detection unit and the cetane number of the fuel detected by the fuel property detection unit Control target value setting means for setting a target opening value (EGRdeg), an EGR cooler target heat release amount (Qclr), and a cylinder intake gas target flow rate (Vcyl) which is a volume flow rate; An intake air flow rate detecting means for detecting an intake air flow rate (Vair1) as a volume flow rate, and an intake air flow rate reference value (Vair0) as a volume flow rate from the detected operating condition and the detected intake air flow rate (Vair1). Intake air reference value detection means for detecting abnormality of the intake air flow rate detection means using the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0), and detected operating conditions are detected. EGR cooler heat release amount detecting means for detecting the EGR cooler heat release amount (Qclr1) from the intake air flow rate (Vair1) and the control target value set by the control target value setting means, and the detected intake air flow rate (Vair1) ) From the EGR path diagnosis means for diagnosing the EGR path abnormality, the diagnosis result of the EGR path diagnosis means and the control target value setting means. EGR control means for performing opening / closing control of the EGR valve based on the control target value set in the step, the control target value set by the control target value setting means, the detected EGR cooler heat release amount (Qclr1), and EGR EGR cooler diagnostic means for diagnosing the cooling efficiency of the EGR cooler based on the diagnostic result of the system path diagnostic means, EGR cooler control means for controlling the cooling efficiency of the EGR cooler based on the diagnostic result of the EGR cooler diagnostic means, It is characterized by having.

  According to the present invention, as shown in FIG. 18, the ignition timing can be controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler. For this reason, the compression end temperature can be controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler corresponding to the increase or decrease of the cetane number of the fuel used and changing the temperature of the working gas sucked into the cylinder. For example, the ignitability can be kept constant by offsetting the influence on the ignitability due to the increase or decrease of the cetane number. That is, when a fuel with a low cetane number is used, the cooling efficiency (heat dissipation amount) of the EGR cooler is reduced, and when a fuel with a high cetane number is used, the cooling efficiency (heat dissipation amount) of the EGR cooler is increased. Therefore, as a result of keeping the ignition timing constant without changing the premixed combustion ratio or the diffusion combustion ratio, there is no fluctuation in combustion noise, NOx, and smoke emission.

  According to the present invention, the abnormality diagnosis of the intake air flow rate detecting means, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler (cooling capacity reduction) 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.

  Further, the EGR cooler 17 is provided with a water amount adjusting means 42. As the water amount adjusting means 42, a proportional solenoid type electromagnetic valve, a control valve driven by a step motor or the like can be used. As will be described later, when the cooling efficiency (heat radiation amount) of the EGR cooler 17 is lowered, the cooling efficiency (heat radiation amount) is recovered to prevent the EGR quality (rate, amount, temperature) from fluctuating. The exhaust performance will not change. Even if the water temperature adjusting means is provided in place of the water amount adjusting means 12, the cooling efficiency (heat radiation amount) can be recovered to prevent the EGR quality (rate, amount, temperature) from fluctuating. 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.

  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.

  An air-fuel ratio sensor 41 for detecting an air-fuel ratio (A / F) is provided at the outlet of the DPF 16, and this signal is also input to the engine control unit 30. As the air-fuel ratio sensor 41, for example, an oxygen ion conductive solid electrolyte is used to detect the oxygen concentration in the exhaust gas and obtain the air-fuel ratio from the oxygen concentration. The air-fuel ratio sensor 41 may be provided at the inlet of the DPF 16.

  Further, 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, DPF temperature Tdpf, and air-fuel ratio A / F 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.

  In S2500, the cetane number is detected. The density of fuel (light oil) and the cetane number have a relationship as shown in FIG. 13. For example, if a map in which the cetane number is determined according to the density of the fuel is provided, the intake air amount Gair is set to the air-fuel ratio A The actual fuel supply weight of the fuel is detected by dividing by / F, and this actual fuel supply weight is divided by the fuel supply amount obtained from the common rail pressure and the valve opening signal to detect the actual specific gravity of the fuel being used. By doing so, the cetane number of the fuel being used can be detected.

  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, diagnosis of the EGR cooler 17 and control of the heat release amount of the EGR cooler 17 are performed. In other words, this S3700 corresponds to the EGR cooler diagnosis means and the EGR cooler control means in FIG.

  In S3800, warning control is performed. In this warning control, for example, when it is determined that the air flow meter 7 is abnormal, for example, a warning light for monitoring is turned on to prompt repair and inspection.

  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.

  With respect to the target heat release amount Qclr of the EGR cooler 17, the compression end temperature rises and the fuel ignitability improves as the engine load, rotation speed, and engine coolant temperature (or EGR cooler coolant temperature) increase. The combustion ratio increases and smoke emissions increase. Therefore, as shown in FIGS. 14 and 15, the temperature of the cylinder intake gas is increased by increasing the target heat release amount Qclr as the engine load, rotation speed, and engine coolant temperature (or EGR cooler coolant temperature) increase. Is set so as to promote the premixing of the injected fuel and to suppress the increase of the smoke emission amount. Further, as described above, with respect to fluctuations in the cetane number of the fuel used, the target heat release amount Qclr is increased as the cetane number increases as shown in FIG.

  That is, the target heat release amount Qclr of the EGR cooler 17 is determined by multiplying Qclr detected from the map data by the cetane number heat release amount coefficient Kcn calculated from FIG. 16 and the water temperature heat release amount coefficient Kwt calculated from FIG. The

  Further, the EGR valve opening target value EGRdeg is corrected by an EGR valve opening target value correction coefficient KEGRdeg and a cetane number EGR correction coefficient KEGRcn described later.

  As shown in FIG. 17, the cetane number EGR correction coefficient KEGRcn is set so as to decrease as the cetane number increases. This is because as the cetane number increases, the target heat release amount Qclr is increased and the temperature of the cylinder intake gas is decreased, so that the EGR rate increases and NOx decreases as shown in FIG. Therefore, it is performed to eliminate the fluctuation of NOx.

  Here, the characteristic line A in FIG. 18 has a normal cooling capacity, the characteristic line B has a slightly lower cooling capacity than a normal one, and the characteristic line C has a lower cooling capacity than a normal one. The ability is greatly reduced.

  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 diagnosis of the EGR cooler 17 and control of the heat release amount of the EGR cooler 17.

  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 predetermined heat radiation amount deviation. If the deviation Qdelta is equal to or larger than the predetermined deviation Qdelta1, the EGR cooler 17 is abnormal (abnormality due to a decrease in cooling efficiency due to coating or accumulation of soot). The process proceeds to S3740.

  On the other hand, when the deviation Qdelta is smaller than the predetermined deviation Qdelta1, it is diagnosed that there is no abnormality in the EGR cooler 17, and the process ends.

  If it is diagnosed that there is an abnormality in the EGR cooler 17, the amount of heat radiation of the EGR cooler 17 is controlled in S3740. That is, when the cooling efficiency (heat radiation amount) of the EGR cooler 17 is lowered, the water amount adjusting means 42 provided in the EGR cooler 17 is controlled so as not to fluctuate the quality (rate, amount, temperature) of the EGR. Then, recover the cooling efficiency (heat dissipation).

  As described above, in the present embodiment, as shown in FIG. 18, the ignition timing can be controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler 17. Therefore, the compression end temperature is controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler 17 corresponding to the increase or decrease of the cetane number of the fuel used and changing the temperature of the working gas sucked into the cylinder. By doing so, it is possible to keep the ignitability constant by offsetting the influence on the ignitability due to the increase or decrease of the cetane number. That is, when a fuel having a low cetane number is used, the cooling efficiency (heat radiation amount) of the EGR cooler 17 is lowered, and when a fuel having a high cetane number is used, the cooling efficiency (heat radiation amount) of the EGR cooler 17 is reduced. By increasing the ignition timing, the ignition timing can be kept constant without changing the premixed combustion ratio or the diffusion combustion ratio. As a result, there is no fluctuation in combustion noise, NOx, and smoke emission.

Then, the abnormality diagnosis of the air flow meter 7, the abnormality diagnosis of the EGR system path, and the abnormality (cooling capacity reduction) diagnosis of the EGR cooler 17 can be performed separately.
For this reason, it is possible to diagnose performance deterioration of the air flow meter 7 (or leakage from the intake system) and troubles in the EGR system (clogging due to system fouling, deterioration of EGR valve opening control accuracy).

  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.

  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 part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system. An EGR passage, an EGR valve provided in the middle of the EGR passage, an EGR cooler for cooling EGR gas, and a fuel property detection means for detecting at least the cetane number among the properties of the fuel used are provided. The intake air target flow rate (Vair), which is a volume flow rate, and the EGR valve opening are applied to the internal combustion engine and are determined according to the operating conditions detected by the operating condition detecting means and the cetane number of the fuel detected by the fuel property detecting means. Control target value setting means for setting a degree target value (EGRdeg), an EGR cooler target heat release amount (Qclr), a cylinder intake gas target flow rate (Vcyl) which is a volume flow rate, and a volume flow rate An intake air flow rate detection means for detecting a certain intake air flow rate (Vair1), and an intake air flow rate reference value (Vair0) that is a volume flow rate are detected from the detected operating conditions and the detected intake air flow rate (Vair1). Intake air reference value detection means for diagnosing abnormality of the intake air flow rate detection means using the intake air flow rate (Vair1) and the intake air flow rate reference value (Vair0), detected operating conditions, and detected intake air EGR cooler heat release amount detecting means for detecting EGR cooler heat release amount (Qclr1) from the flow rate (Vair1) and the control target value set by the control target value setting means, and EGR from the detected intake air flow rate (Vair1). Set by EGR path diagnosis means for diagnosing abnormality of the system path, diagnosis result of EGR path diagnosis means and control target value setting means EGR control means for performing opening / closing control of the EGR valve based on the control target value, the control target value set by the control target value setting means, the detected EGR cooler heat radiation amount (Qclr1), and the EGR path diagnosis means And an EGR cooler diagnosis means for performing a cooling efficiency diagnosis of the EGR cooler based on the diagnosis result, and an EGR cooler control means for performing a cooling efficiency control of the EGR cooler based on the diagnosis result of the EGR cooler diagnosis means.

  As a result, as shown in FIG. 18, the ignition timing can be controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler. For this reason, the compression end temperature can be controlled by changing the cooling efficiency (heat radiation amount) of the EGR cooler corresponding to the increase or decrease of the cetane number of the fuel used and changing the temperature of the working gas sucked into the cylinder. For example, the ignitability can be kept constant by offsetting the influence on the ignitability due to the increase or decrease of the cetane number. That is, when a fuel with a low cetane number is used, the cooling efficiency (heat dissipation amount) of the EGR cooler is reduced, and when a fuel with a high cetane number is used, the cooling efficiency (heat dissipation amount) of the EGR cooler is increased. As a result, the ignition timing can be kept constant without changing the premixed combustion ratio or the diffusion combustion ratio, so that there is no fluctuation in combustion noise, NOx, and smoke emission.

  According to the present invention, the abnormality diagnosis of the intake air flow rate detecting means, the abnormality diagnosis of the EGR system path, and the abnormality diagnosis of the EGR cooler (cooling capacity reduction) 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 described in (1) above, the EGR cooler diagnosis means includes an EGR cooler target heat release amount (corresponding to an operating condition and a cetane number detected by the fuel property detection means ( If the EGR cooler heat release amount deviation (Qdelta), which is the deviation of the calculated EGR cooler heat release amount (Qclr1), is less than the allowable heat release amount deviation (Qdelta1), the cooling efficiency of the EGR cooler is appropriate. If it is diagnosed that there is a deviation in heat dissipation amount (Qdelta1), the cooling efficiency of the EGR cooler is diagnosed as inappropriate.

  (3) In the exhaust gas recirculation control device for an internal combustion engine according to (1) or (2), the EGR cooler control means includes a cooling water temperature adjusting means or a cooling water amount adjusting means, and operating conditions and fuel property detection EGR cooler heat dissipation amount (Qdelta) which is a deviation of the calculated EGR cooler heat dissipation amount (Qclr1) with respect to the EGR cooler target heat dissipation amount (Qclr) determined according to the fuel property (cetane number) detected by the means ) Is equal to or greater than the allowable heat radiation amount deviation (Qdelta1), the cooling efficiency of the EGR cooler is controlled by adjusting the cooling water temperature or the cooling water amount according to the heat radiation amount deviation (Qdelta).

  (4) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (3), the control target value setting means increases the EGR cooler target as the cetane number detected by the fuel property detection means increases. Increase heat dissipation (Qclr).

  (5) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (4), the operating condition detecting means detects at least the engine load, the rotational speed, and the engine coolant temperature, and the control target The value setting means increases and sets the EGR cooler target heat release amount (Qclr) as the engine load, the rotation speed, and the coolant temperature detected by the operating condition detection means increase.

  (6) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (5), the intake air flow rate detection means detects the intake fresh air amount for detecting the intake fresh air amount (Gair) of the internal combustion engine. The apparatus includes a detection means, an intake fresh air temperature detection means for detecting the intake fresh air temperature, an intake fresh air pressure detection means for detecting the intake fresh air pressure, and the detected intake fresh air amount (Gair) and the intake fresh air. The intake air flow rate calculation means calculates the intake air flow rate (Vair1) based on the temperature and the intake fresh air pressure.

  (7) In the exhaust gas recirculation control apparatus for an internal combustion engine according to any one of (1) to (6), the intake air reference value detection means detects a total travel distance (Run) from a new vehicle state of the vehicle. When the detected total travel distance (Run) is equal to or less than a predetermined value (Run1), a predetermined distance is determined 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 operating conditions, and when the travel distance exceeds the predetermined value (Run1), the intake air flow rate reference value (Vair0) that is currently set If the detected deviation (Vadlt) of the intake air flow rate (Vair1) is equal to or smaller than the predetermined deviation (Vadlt1), there is no abnormality in the intake air flow rate detection means, and the deviation (Vadlt1) is greater than or equal to the predetermined deviation (Vadlt1). Having an intake air reference value setting diagnosing means diagnoses that there is an abnormality in the intake air flow rate detecting means if Re.

  (8) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (7), 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). From the EGR flow rate calculating means for calculating (Gegr1), the 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 temperature before and after the EGR cooler EGR cooler heat dissipation amount calculation means for calculating an EGR cooler heat dissipation amount (Qclr1).

  (9) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (8), the EGR path diagnosis means detects the 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). Diagnose that there is an abnormality in the EGR system.

  (10) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (9), the EGR control means is determined by operating conditions when it is diagnosed that the EGR system path is abnormal. The intake air flow rate is recovered so that the detected intake air flow rate (Vair1) deviation (Vdelta) is equal to or smaller than the allowable intake air flow rate deviation (Vdelta1) with respect to the intake air target flow rate (Vair). .

  (11) In the exhaust gas recirculation control device for an internal combustion engine according to any one of (1) to (10), 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).

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 diagnosis and the amount-of-heat-control of EGR cooler. The characteristic view which shows correlation with a cetane number and the density of light oil. The characteristic view which shows correlation with an engine load, rotation speed, and target heat radiation amount Qclr. The characteristic view which shows the correlation with water temperature thermal radiation coefficient Kwt and engine cooling water temperature. The characteristic view which shows correlation with the cetane number heat radiation coefficient Kcn and a cetane number. The characteristic view which shows the correlation of cetane number EGR correction coefficient KEGRcn and cetane number. Explanatory drawing which showed typically the change of the ignition timing when changing the cooling efficiency of an EGR cooler according to the increase / decrease in cetane number. Explanatory drawing which showed typically the change of the ignition timing according to increase / decrease in cetane number. 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 (11)

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 and a fuel property detection means for detecting at least a cetane number among the properties of the fuel being used,
Intake air target flow rate (Vair) and EGR valve opening target value (EGRdeg), which are volumetric flow rates, according to the operating conditions detected by the operating condition detection means and the cetane number of the fuel detected by the fuel property detection means Control target value setting means for setting an EGR cooler target heat release amount (Qclr) and a cylinder intake gas target flow rate (Vcyl) which 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;
From the detected operating condition and the detected intake air flow rate (Vair1), an intake air flow rate reference value (Vair0) which is a volume flow rate is detected, and the intake air flow rate (Vair1) and intake air flow rate reference value (Vair0) An intake air reference value detecting means for performing abnormality diagnosis of the intake air flow rate detecting means using
EGR cooler heat release amount detecting 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 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 diagnosis for diagnosing the cooling efficiency of the EGR cooler based on the control target value set by the control target value setting means, the detected EGR cooler heat release amount (Qclr1), and the diagnosis result of the EGR path diagnosis means 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 diagnostic means is a deviation of the calculated EGR cooler heat dissipation amount (Qclr1) with respect to the EGR cooler target heat dissipation amount (Qclr) determined according to the operating conditions and the cetane number detected by the fuel property detection means. If the EGR cooler heat dissipation amount deviation (Qdelta) is less than the allowable heat dissipation amount deviation (Qdelta1), the cooling efficiency of the EGR cooler is diagnosed as appropriate, and if it is greater than the heat dissipation amount deviation (Qdelta1), the EGR cooler is cooled. The exhaust gas recirculation control apparatus for an internal combustion engine according to claim 1, wherein the efficiency is diagnosed as inappropriate. The EGR cooler control means has a cooling water temperature adjusting means or a cooling water amount adjusting means,
This is a deviation of the calculated EGR cooler heat dissipation amount (Qclr1) from the EGR cooler target heat dissipation amount (Qclr) determined according to the operating condition and the fuel property (cetane number) detected by the fuel property detecting means. If the EGR cooler heat radiation amount deviation (Qdelta) is equal to or greater than the allowable heat radiation amount deviation (Qdelta1), the cooling efficiency control of the EGR cooler is performed by adjusting the cooling water temperature or the cooling water amount according to the heat radiation amount deviation (Qdelta). The exhaust gas recirculation control apparatus for an internal combustion engine according to claim 1 or 2.   The internal combustion engine according to any one of claims 1 to 3, wherein the control target value setting means increases the EGR cooler target heat release amount (Qclr) as the cetane number detected by the fuel property detection means increases. Engine exhaust gas recirculation control device. The operating condition detection means detects at least the engine load, rotation speed, engine coolant temperature,
The control target value setting means increases and sets the EGR cooler target heat dissipation amount (Qclr) as the engine load, the rotational speed, and the coolant temperature detected by the operating condition detection means increase. The exhaust gas recirculation control apparatus for an internal combustion engine according to any one of?   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. 6. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation control device is an internal combustion engine.   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, 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); 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 8. An exhaust gas recirculation control device for an internal combustion engine according to any one of Items 1 to 7.   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 intake air target flow rate (Vair) determined by the operating conditions. The EGR system path is diagnosed as being abnormal if there is any, and the EGR system path is diagnosed as being abnormal if the intake air flow rate deviation (Vdelta1) is greater than or equal to. An exhaust gas recirculation control device for an internal combustion engine.   When the EGR control means is diagnosed as having an abnormality in the EGR system path, the deviation (Vdelta) of the detected intake air flow rate (Vair1) with respect to the intake air target flow rate (Vair) determined by the operating conditions is The exhaust gas recirculation control apparatus for an internal combustion engine according to any one of claims 1 to 9, wherein a recovery process of the intake air flow rate is performed so that an allowable intake air flow rate deviation (Vdelta1) is less than or equal to.   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 11. An exhaust gas recirculation control device for an internal combustion engine according to any one of Items 1 to 10.

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