JP4305121B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control applied to an internal combustion engine having a blow-by gas recirculation device and diagnosing an abnormality in a fuel supply system based on a deviation amount from a reference value of a parameter representing a concentration state of an air-fuel mixture in a combustion chamber. It relates to the device.

  In an internal combustion engine equipped with a three-way catalyst, air-fuel ratio feedback control is generally performed to effectively maintain the exhaust purification function of the three-way catalyst. In this control, an air-fuel ratio, which is a mixture ratio of intake air and injected fuel, is detected by an oxygen sensor provided in the exhaust passage, and a feedback correction value FAF corresponding to the air-fuel ratio is used in accordance with the engine operating state at that time. The basic fuel injection amount is corrected. For example, when the air-fuel ratio is richer than the stoichiometric air-fuel ratio and a rich signal is output from the oxygen sensor, the feedback correction value FAF is decreased. When the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and the lean signal is output from the oxygen sensor, the feedback correction value FAF is increased. The energization of the fuel injection valve for each cylinder is controlled based on the injection amount (indicated injection amount) corrected by the feedback correction value FAF, so that the fuel injection amount of each cylinder is corrected to decrease or increase, and The air / fuel ratio is converged to the stoichiometric air / fuel ratio.

  In the air-fuel ratio feedback control described above, if there is no abnormality in the fuel supply system such as the fuel injection valve and the fuel injection is normally performed, the basic injection amount and the command injection amount become the same value, and the feedback correction value FAF does not deviate significantly from the reference value. Therefore, when the amount of deviation of the feedback correction value FAF from the reference value is larger than a predetermined value, it is diagnosed that the fuel supply system is abnormal.

  By the way, in an internal combustion engine in which blow-by gas (unburned mixture or combustion gas) leaked from the combustion chamber to the crank chamber through the space between the piston and the cylinder wall is returned to the ventilation passage and recombusted, In some cases, the fuel in the blow-by gas is supplied to the combustion chamber in addition to the fuel injected from the injection valve.

  However, in the air-fuel ratio feedback control described above, the fuel injected from the fuel injection valve is taken into consideration, but the fuel content in the blow-by gas is not taken into consideration. The amount of fuel injected from the fuel injection valve (indicated injection amount) can be reduced by the amount of fuel in the blowby gas. A large feedback correction value FAF is used in order to obtain such a small amount of command injection. If the feedback correction value FAF having a large amount of deviation from the reference value is used, there is a risk that the abnormality is actually diagnosed even though the fuel supply system is normal.

  In order to prevent erroneous diagnosis, for example, as described in Patent Document 1, it is conceivable that the abnormality diagnosis of the fuel supply system is stopped when the fuel concentration in the blow-by gas is higher than a reference value.

In addition, as a prior art document concerning this invention, in addition to the patent document 1 mentioned above, the following patent document 2 is mentioned.
Japanese Patent No. 2917725 JP-A-10-317936

  However, as described above, if the diagnosis is always stopped when the fuel concentration in the blow-by gas is high, the chances of diagnosing the fuel supply system are reduced. Such a problem is particularly likely to occur in a direct injection internal combustion engine that directly injects fuel into the combustion chamber. In this type of internal combustion engine, compared to a port injection type internal combustion engine that injects fuel into the intake port, the injected fuel spray tends to adhere to the cylinder wall surface. This is because it is scraped off by sliding, gets back on the blow-by gas and returns to the combustion chamber through the intake passage, and the fuel concentration tends to increase.

  The present invention has been made in view of such circumstances, and an object of the present invention is to avoid the possibility of diagnosis while suppressing erroneous diagnosis of the fuel supply system caused by the recirculation of blow-by gas. An object of the present invention is to provide a control device for an internal combustion engine.

In the following, means for achieving the above object and its effects are described.
In the first aspect of the invention, a blow-by gas recirculation device that recirculates the blow-by gas to the intake system is provided, and the fuel supply system is based on the deviation from the reference value of the parameter that represents the concentration state of the air-fuel mixture in the combustion chamber. The blow-by gas recirculation device includes a recirculation amount adjustment valve that adjusts the recirculation amount of the blow-by gas, and the recirculation amount of the blow-by gas is determined as the engine operating state at that time. And a recirculation control means for setting a recirculation amount of blow-by gas within a range in which a deviation amount of the parameter from the reference value does not exceed a predetermined value at the time of diagnosis of the fuel supply system, and the fuel Prior to diagnosis of the supply system, when the internal combustion engine is operated in a predetermined operation region in which the deviation amount of the parameter from the reference value is large And a valve-opening means for forcedly opening the serial recirculation amount adjusting valve, the recirculation control means sets the recirculation amount, when the deviation amount from the reference value of the parameter is greater than a predetermined value Assume that the blow-by gas recirculation device is controlled so that the recirculation amount of the blow-by gas is reduced, assuming that the predetermined operating condition is satisfied . Here, as the predetermined value, for example, a value that diagnoses that the fuel supply system is abnormal when the amount of deviation from the reference value is larger than this value is used. Further, the parameter representing the concentration state is a feedback correction value used when the fuel injection amount is feedback-controlled so as to converge the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio, as in the second aspect of the invention. It is done.

According to the configuration of the first aspect of the present invention, when the internal combustion engine is operated, the recirculation amount of the blow-by gas is set according to the engine operating state at that time, and the parameter indicating the concentration state of the air-fuel mixture in the combustion chamber is set . An abnormality in the fuel supply system is diagnosed based on the amount of deviation from the reference value. That is , when the deviation amount exceeds the predetermined value, a diagnosis is made that it is abnormal.

  By the way, in the internal combustion engine provided with the blow-by gas recirculation device, if the fuel is contained in the blow-by gas recirculated to the intake system, this fuel affects the above-described concentration state of the air-fuel mixture. If the amount of deviation of the affected parameter from the reference value is used for diagnosis, there is a risk of erroneous diagnosis that the fuel supply system is abnormal although it is normal.

  Here, if the amount of recirculation of the blow-by gas is changed, the magnitude of the influence of the fuel contained in the blow-by gas on the concentration state of the air-fuel mixture changes, and accordingly, the amount of deviation from the reference value of the parameter May change and the diagnostic results may differ.

In this regard, in the invention according to claim 1, while the recirculation amount of the blow-by gas is set according to the engine operating state at that time, when the abnormality of the fuel supply system is diagnosed, the reference value of the parameter is used. The recirculation amount of blow-by gas is set in a range in which the amount of deviation does not exceed a predetermined value. This is synonymous with setting a limit value (allowable range) of the amount of parameter deviation caused by blow-by gas, and changing the recirculation amount of the blow-by gas within a range where the parameter falls within the allowable range. The limit value (allowable range) is a value (range) that can be taken by the amount of parameter deviation caused by blow-by gas under the condition that no erroneous diagnosis is caused. Further, the change in the reflux amount here includes not only a decrease but also an increase. Therefore, by setting (changing) the recirculation amount within the above range, the influence of the fuel in the blow-by gas on the concentration state of the air-fuel mixture is reduced, and the result of the fuel supply system diagnosis performed based on the deviation amount Can be made highly accurate.

According to the first aspect of the present invention, the diagnosis is not stopped even if the fuel concentration in the blow-by gas becomes high.
As described above, according to the first aspect of the present invention, it is possible to avoid the chance of diagnosis while suppressing the erroneous diagnosis of the fuel supply system caused by the recirculation of blow-by gas.

Further , according to the above configuration, the recirculation control means is configured so that the recirculation amount of the blow-by gas is reduced, assuming that the predetermined operation condition is satisfied when the deviation amount of the parameter from the reference value is larger than the predetermined value. Thus, the blow-by gas recirculation device is controlled. By reducing the recirculation amount in this way, the influence of the fuel in the blow-by gas on the concentration state of the air-fuel mixture is reduced. For this reason, after the reduction of the recirculation amount by the above control, the diagnosis result of the fuel supply system performed based on the deviation amount becomes highly accurate.

That is, according to the above configuration, when abnormality of the fuel supply system is diagnosed, if the amount of deviation from the reference value of the parameter is larger than a predetermined value, the recirculation amount is reduced so that the recirculation amount of the blowby gas is reduced. The blow-by gas recirculation device is controlled by the control means. It can be said that the fuel supply system is normal when the amount of deviation is less than or equal to the predetermined value by the control from a state where the amount of deviation is larger than the predetermined value. On the other hand, if the deviation is still larger than the predetermined value even if the control is performed from a state where the deviation is larger than the predetermined value, it can be said that the fuel supply system is abnormal. For this reason, it is possible to more accurately diagnose the abnormality of the fuel supply system by comparing the deviation amount and the predetermined value after the reduction of the recirculation amount.

On the other hand, in the invention according to claim 1, the blow-by gas recirculation device includes a recirculation amount adjusting valve for adjusting a recirculation amount of the blow-by gas, and from the reference value of the parameter prior to diagnosis of the fuel supply system. the internal combustion engine in a predetermined operating region where the amount of deviation becomes larger Ru further comprising opening means for opening the recirculation amount adjusting valve when being operated.

Here, if the recirculation amount adjusting valve is opened in a region where the deviation amount from the reference value of the parameter becomes large, the blow-by gas is recirculated to the intake system, and the deviation amount tends to become larger than a predetermined value.
In this regard, according to the first aspect of the present invention, prior to the diagnosis of the fuel supply system, it is determined whether or not the internal combustion engine is operated in a predetermined operation region in which the amount of deviation from the reference value of the parameter becomes large. When it is determined that the engine is operating in the predetermined operation region, the recirculation amount adjusting valve is forcibly opened by the valve opening means. According to the third aspect of the present invention, when the internal combustion engine is in an idle state, it can be assumed that the engine is operated in a predetermined operation region in which the deviation amount increases. Therefore, by opening the recirculation amount adjusting valve in such a predetermined operation region, the deviation amount from the reference value of the parameter can be made larger than the predetermined value, and a situation where the predetermined operation condition is satisfied can be surely created. .

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the recirculation control means is configured to recirculate blowby gas by the blowby gas recirculation device in response to establishment of the predetermined operating condition. Is prohibited.

  According to the above configuration, when a predetermined operating condition of the internal combustion engine is satisfied, the recirculation of blow-by gas by the blow-by gas recirculation device is prohibited. If the blow-by gas does not recirculate due to this prohibition, the fuel in the blow-by gas will not flow into the combustion chamber. The influence of the fuel in the blow-by gas on the concentration state of the air-fuel mixture is reduced or eliminated. Accordingly, it is possible to more accurately diagnose whether or not the fuel supply system is abnormal based on the amount of deviation from the reference value of the parameter. It is possible to reliably suppress misdiagnosis even under circumstances where erroneous diagnosis results are likely to be generated.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the recirculation control means is configured to operate the internal combustion engine in an operation region other than the predetermined operation region after the prohibition of recirculation of the blowby gas is started. It is assumed that recirculation of the blow-by gas is resumed on the condition.

  When the recirculation of blow-by gas is prohibited, the fuel that adheres to the cylinder wall surface and is scraped off by the sliding of the piston and is normally returned to the combustion chamber together with the blow-by gas is not discharged from the internal combustion engine (crank chamber). Mixed with engine oil. This mixing may dilute the engine oil and reduce the viscosity, which may reduce the lubrication performance.

In contrast, in the invention according to claim 5 , when the internal combustion engine is operated in an operation region other than the predetermined operation region after the prohibition of the recirculation of blow-by gas is started, the recirculation of the blow-by gas is resumed by the recirculation control means. . Here, as in the sixth aspect of the present invention, a region where the amount of deviation from the reference value of the parameter is smaller than a predetermined value can be set as an operation region other than the predetermined operation region . If the fuel supply system is normal, when the recirculation is resumed, the deviation from the reference value of the parameter is small due to the recirculation prohibition performed before that. For this reason, there is little possibility that the fuel supply system is erroneously diagnosed due to the resumption of recirculation of blow-by gas. Therefore, the fuel in the blow-by gas that causes the engine oil to be diluted can be guided to the combustion chamber and burned while suppressing erroneous diagnosis of the fuel supply system.

According to a seventh aspect of the invention, in the invention according to the fifth or sixth aspect , when the recirculation is resumed, the recirculation control means determines that the recirculation amount of the blowby gas is greater than the amount corresponding to the engine operating state at that time. It is assumed that the blow-by gas recirculation device is controlled so as to increase the amount.

  According to the above configuration, when recirculation is resumed, the recirculation amount of the blow-by gas is increased by the recirculation control means to be greater than the amount corresponding to the operating state of the internal combustion engine at that time. Therefore, the fuel in the blow-by gas retained in the internal combustion engine during the recirculation prohibition period can be quickly discharged from the internal combustion engine when recirculation is resumed, so that oil dilution by the fuel can be quickly eliminated.

According to an eighth aspect of the present invention, in the fourth aspect of the present invention, the apparatus further includes a concentration increase suppressing means for suppressing an increase in fuel concentration in the blowby gas while the recirculation control means prohibits recirculation.

  The recirculation of the blow-by gas is prohibited when the predetermined operating condition is satisfied, that is, when the deviation amount from the reference value of the parameter indicating the concentration state is large. This prohibition of reflux should normally reduce the amount of deviation and make the prohibition of reflux unnecessary. However, if a phenomenon that raises the concentration of fuel in the blow-by gas while prohibiting recirculation occurs, the amount of deviation immediately increases when recirculation is prohibited and recirculation is resumed. It is necessary to prohibit the reflux of blow-by gas.

In this regard, in the invention described in claim 8 , when the recirculation is prohibited, the progress of the fuel concentration increase in the blow-by gas is suppressed by the concentration increase suppressing means. For this reason, it is possible to prevent the phenomenon that the deviation amount increases immediately after the reflux of the blow-by gas is prohibited, and to prevent the reflux prohibition from being performed unnecessarily.

The invention according to claim 9 is the invention according to claim 8 , wherein the internal combustion engine injects fuel into the combustion chamber through a first fuel injection valve that directly injects fuel into the combustion chamber and an intake passage. A second fuel injection valve as the fuel supply system, and the concentration increase suppression means prohibits fuel injection from the first fuel injection valve while the recirculation control means prohibits recirculation. .

In the invention according to claim 10 , in the invention according to claim 8 , the internal combustion engine injects fuel into the combustion chamber through a first fuel injection valve that directly injects fuel into the combustion chamber and an intake passage. A second fuel injection valve that injects as the fuel supply system, and the concentration increase suppression means includes both the first fuel injection valve and the second fuel injection valve while the recirculation control means prohibits recirculation. Assume that the injection ratio, which is the ratio of the injected fuel amount of the first fuel injection valve to the injected fuel amount, is reduced.

  Here, when recirculation of blow-by gas is prohibited, when fuel is directly injected from the first fuel injection valve into the combustion chamber, the fuel spray tends to adhere to the wall surface of the cylinder. The attached fuel is scraped off by the piston ring as the piston reciprocates, and is returned to the combustion chamber through the intake passage by riding on blow-by gas. As a result, when the concentration of the fuel increases, when the recirculation prohibition ends and the recirculation is resumed, the deviation amount immediately increases, and it is necessary to prohibit the recirculation of the blow-by gas again.

In this regard, in the invention described in claim 9 , when the recirculation is prohibited, the fuel injection from the first fuel injection valve is prohibited by the concentration increase suppression means. In the invention according to claim 10 , when the recirculation is prohibited, the injection ratio of the first fuel injection valve is made small by the concentration increase suppressing means. In either case, the amount of fuel adhering to the wall surface of the cylinder, and hence the amount of fuel scraped off by the piston ring is reduced, and the progress of the increase in fuel concentration in the blow-by gas is suppressed. For this reason, it is possible to prevent the phenomenon that the amount of deviation increases immediately after the reflux of the blow-by gas is prohibited, and to reliably prevent the reflux prohibition from being performed unnecessarily.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. As shown in FIGS. 1 and 2, a vehicle is equipped with a gasoline engine (hereinafter simply referred to as an engine) 11 as an internal combustion engine. The engine 11 includes a cylinder block 13 having a plurality of cylinders (cylinders) 12. A crankcase 14 and an oil pan 15 are attached to the lower side of the cylinder block 13, and a cylinder head 16 is attached to the upper side. A piston 17 is accommodated in each cylinder 12 so as to reciprocate. Each piston 17 is connected to a crankshaft 19 that is an output shaft of the engine 11 via a connecting rod 18. Therefore, the reciprocating motion of each piston 17 is converted into rotational motion by the connecting rod 18 and then transmitted to the crankshaft 19.

  An intake passage 22 and an exhaust passage 23 are connected to the combustion chamber 21 of each cylinder 12. Air outside the engine 11 is taken into the combustion chamber 21 through the intake passage 22 and is generated in the combustion chamber 21. The exhaust is discharged to the exhaust passage 23. The cylinder head 16 is provided with an intake valve 24 that opens and closes between the intake passage 22 and the combustion chamber 21 and an exhaust valve 25 that opens and closes between the exhaust passage 23 and the combustion chamber 21, respectively. The intake valve 24 is driven by an intake camshaft 26 that rotates in conjunction with the crankshaft 19. The exhaust valve 25 is driven by an exhaust camshaft 27 that rotates in conjunction with the crankshaft 19.

  A throttle valve 28 is rotatably provided in the intake passage 22. An actuator 29 such as a motor is drivingly connected to the throttle valve 28. The amount of air flowing through the intake passage 22 varies according to the rotation angle (throttle opening) of the throttle valve 28. The throttle opening is adjusted by driving the actuator 29 in accordance with the amount of depression of the accelerator pedal 31 operated by the driver.

  An electromagnetic fuel injection valve 32 is attached to the engine 11 corresponding to each cylinder 12. Each fuel injection valve 32 is supplied with high-pressure fuel discharged from a fuel pump (not shown). Each fuel injection valve 32 is controlled to open and close, thereby directly injecting and supplying high-pressure fuel to the corresponding combustion chamber 21. These fuel pumps and fuel injection valves 32 constitute a part of the fuel supply system. The fuel injected from the fuel injection valve 32 is mixed with the air in the combustion chamber 21 to become an air-fuel mixture.

  A spark plug 34 is attached to the engine 11 corresponding to each cylinder 12. The spark plug 34 is driven based on the ignition signal from the igniter 35. A high voltage output from the ignition coil 36 is applied to the spark plug 34. The air-fuel mixture is ignited by the spark discharge of the spark plug 34 and explodes and burns. The piston 17 is reciprocated by the high-temperature and high-pressure combustion gas generated at this time, the crankshaft 19 is rotated, and the driving force (output torque) of the engine 11 is obtained.

  In the engine 11, gas leaks into the crank chamber 37 from the gap between the wall surface of the cylinder 12 and the piston 17 in the compression stroke and the expansion stroke. This gas consists of an air-fuel mixture that leaks in the compression stroke, a combustion gas that leaks in the expansion stroke, and the like, and is called blow-by gas. Since blow-by gas can cause engine oil (engine oil) to deteriorate and rust the inside of the engine 11, the blow-by gas is returned to the intake system by the blow-by gas recirculation device 38 as shown in FIG. ) Recombustion is performed in the combustion chamber 21. The crank chamber 37 is a space in which the crankshaft 19 is accommodated, and is a space surrounded by the cylinder block 13, the crankcase 14, the oil pan 15, and the like.

  The blow-by gas recirculation device 38 includes a blow-by gas passage 41 that connects the crank chamber 37 and, for example, a surge tank 39 downstream of the throttle valve 28 in the intake passage 22. In the blowby gas recirculation device 38, a negative pressure (pressure lower than the atmospheric pressure) generated downstream of the throttle valve 28 acts on the crank chamber 37 through the blowby gas passage 41. A PCV valve 42 is provided in the middle of the blow-by gas passage 41 as a recirculation amount adjusting valve for adjusting the recirculation amount of the blow-by gas. The PCV valve 42 is composed of an electromagnetic valve that opens and closes a valve body connected to the movable iron core when the movable iron core in the electromagnetic coil is attracted or separated by an exciting current. In the PCV valve 42, the position of the valve body is changed by controlling the energization to the electromagnetic coil, and the flow passage area of the blow-by gas passage 41 is changed accordingly. By this change, the reflux amount of blow-by gas is adjusted.

  Further, the blow-by gas recirculation device 38 introduces air outside the engine 11 (also referred to as fresh air) into the crank chamber 37 in order to reduce the concentration of blow-by gas (particularly nitrogen oxide NOx) in the crank chamber 37. The air introduction passage 43 is provided. One end of the air introduction passage 43 is connected upstream of the throttle valve 28 in the intake passage 22, and the other end is connected to the crank chamber 37 through the head cover 20, the cylinder head 16, the cylinder block 13, and the like.

  According to this blow-by gas recirculation device 38, blow-by gas and fresh air flow as shown in FIG. In FIG. 2, the solid line arrows indicate the flow of blow-by gas, and the broken line arrows indicate the flow of fresh air. When the engine 11 is under a low load, a negative pressure downstream of the throttle valve 28 acts in the crank chamber 37 through the blow-by gas passage 41 and the PCV valve 42. Due to this negative pressure, the blow-by gas in the crank chamber 37 is sucked into the combustion chamber 21 through the blow-by gas passage 41, the PCV valve 42 and the intake passage 22. Also, fresh air is sucked into the crank chamber 37 through the air introduction passage 43 by the negative pressure.

  On the other hand, when the engine 11 is at a high load, the negative pressure downstream of the throttle valve 28 is reduced, while the amount of blow-by gas generated is increased. For this reason, the blowby gas not only flows downstream from the throttle valve 28 in the intake passage 22 through the blowby gas passage 41 but also flows backward from the air introduction passage 43 and upstream from the throttle valve 28 in the intake passage 22.

  As shown in FIG. 1, the vehicle is provided with various sensors for detecting the operating state of the engine 11. For example, a crank angle sensor 44 that generates a pulse signal every time the crankshaft 19 rotates by a certain angle is provided in the vicinity of the crankshaft 19. The signal of the crank angle sensor 44 is used for calculating the crank angle that is the rotation angle of the crankshaft 19 and the engine rotation speed that is the rotation speed of the crankshaft 19 per unit time.

  An intake pressure sensor 45 for detecting the pressure of intake air (intake pressure) is provided downstream of the throttle valve 28 in the intake passage 22. An accelerator sensor 46 that detects the amount of depression of the accelerator pedal 31 by the driver is provided at or near the accelerator pedal 31. A throttle sensor 47 that detects the throttle opening is provided in the vicinity of the throttle valve 28. In the middle of the exhaust passage 23, an oxygen sensor 48 for detecting the oxygen concentration in the exhaust is provided. The output signal of the oxygen sensor 48 is used to determine whether the air-fuel mixture is rich (rich) or thin (lean) with respect to the stoichiometric air-fuel ratio.

  In order to control each part of the engine 11 based on the detection values of the various sensors 44 to 48 described above, an electronic control unit (ECU) 50 configured with a microcomputer as a center is provided. In the ECU 50, a central processing unit (CPU) performs arithmetic processing according to a control program and initial data stored in a read-only memory (ROM), and executes various controls based on the calculation results. The calculation result by the CPU is temporarily stored in a random access memory (RAM).

  Examples of the control performed by the ECU 50 include fuel injection control of the engine 11, ignition timing control, valve opening amount control of the PCV valve 42, abnormality diagnosis of the fuel supply system, and the like. For example, when the valve opening amount of the PCV valve 42 is controlled, the valve opening amount corresponding to the operating state of the engine 11 at that time is calculated. For this calculation, for example, a map (not shown) for determining the valve opening amount that predefines the relationship between the intake pressure corresponding to the engine load and the valve opening amount can be referred to. Then, the valve opening amount determined from this map is used as an instruction valve opening amount for instructing the PCV valve 42, and the energization to the PCV valve 42 is controlled based on the instruction valve opening amount. By this energization, the valve opening amount of the PCV valve 42 is adjusted, and a desired amount of blow-by gas is recirculated to the intake passage 22.

  In addition, the ECU 50 calculates the fuel injection amount (basic injection amount) and the injection timing based on the operating state of the engine 11 such as the engine speed and the engine load when the air-fuel mixture is burned at a predetermined air-fuel ratio during fuel injection control. To do. The engine load is obtained based on, for example, parameters related to the intake air amount of the engine 11 (throttle opening, accelerator depression amount, intake pressure, etc.).

  Further, when the engine 11 is in a stable operation state after the warm-up is completed, the ECU 50 performs air-fuel ratio feedback control for accurately matching the air-fuel ratio to the theoretical air-fuel ratio that is the target value. This air-fuel ratio feedback control is to increase or decrease the basic injection amount depending on whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, and is performed according to the following equation.

Instructed injection amount = Basic injection amount · {1+ (FAF / 100)} (i)
In the above formula (i), “FAF” is a correction value (feedback correction value) for compensating for the deviation through feedback control when the air-fuel ratio shifts transiently from the theoretical air-fuel ratio.

  The feedback correction value FAF is made smaller when the air-fuel ratio is richer than the stoichiometric air-fuel ratio. Then, by driving and controlling each fuel injection valve 32 based on the command injection amount calculated by the above formula (i), the fuel injection amount for each cylinder is corrected to decrease, and the air-fuel ratio is adjusted to the lean side. Further, when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the feedback correction value FAF is increased. Then, by driving and controlling each fuel injection valve 32 based on the command injection amount calculated by the above formula (i), the fuel injection amount for each cylinder is corrected to be increased, and the air-fuel ratio is adjusted to the rich side.

  Thus, the air-fuel ratio of the air-fuel mixture supplied to the engine 11 is detected based on the oxygen concentration by the oxygen sensor 48, and the basic injection amount is corrected based on the feedback correction value FAF corresponding to the detected air-fuel ratio. . By making the corrected fuel injection amount the fuel injection amount (indicated injection amount) supplied to the engine 11, the air-fuel ratio of the air-fuel mixture is converged to the stoichiometric air-fuel ratio.

  In the air-fuel ratio feedback control described above, if there is no abnormality in the fuel supply system such as the fuel injection valve 32 and the fuel injection is performed normally, the basic injection amount and the commanded injection amount become the same value, and the feedback correction The value FAF does not deviate significantly from the reference value A (for example, “0”). Therefore, the ECU 50 diagnoses that the fuel supply system is abnormal when the deviation amount of the feedback correction value FAF from the reference value A is larger than a predetermined determination value (for example, 35%), and turns on the warning lamp. Etc. so as to notify the passenger of the abnormality.

  By the way, in the engine 11 of this embodiment provided with the blow-by gas recirculation device 38, the fuel in the blow-by gas flows into the combustion chamber 21 in addition to the fuel injected from the fuel injection valve 32. However, in the air-fuel ratio feedback control described above, the fuel and the fuel injected from the fuel injection valve 32 are considered, but the fuel content in the blow-by gas is not considered. The amount of fuel injected from the fuel injection valve 32 (indicated injection amount) can be reduced by the amount of fuel in the blowby gas. A large feedback correction value FAF is used in order to obtain such a small amount of command injection. If the feedback correction value FAF having a large deviation from the reference value A is used, there is a risk that the abnormality is actually diagnosed even though the fuel supply system is normal. This problem is particularly likely to occur in the in-cylinder injection engine 11 in which fuel is directly injected into the combustion chamber 21 as in the present embodiment. In this type of engine 11, the injected fuel spray easily adheres to the wall surface of the cylinder 12 as compared with the port injection type engine 11, and this attached fuel is scraped off by the piston ring as the piston 17 reciprocates. This is because the scraped fuel rides on the blow-by gas and is returned to the combustion chamber 21 through the intake passage 22 to easily increase the fuel concentration.

  Therefore, in the present embodiment, control for suppressing such misdiagnosis is performed. Next, the contents of this misdiagnosis suppression control will be described with reference to the flowchart of FIG.

  First, in step 100, the ECU 50 determines whether or not the engine 11 is operated in an operation region in which the deviation amount of the feedback correction value FAF from the reference value A (= 0) tends to be large. Here, the feedback correction value FAF can be expressed by the following equation (ii) by rewriting the above-described equation (i).

FAF = {(indicated injection amount−basic injection amount) / basic injection amount} · 100 (ii)
From the above equation (ii), the feedback correction value FAF increases as the basic injection amount decreases. An example of the operation region where the basic injection amount is small is an idle state. Therefore, in step 100, it is determined whether or not the operating state of the engine 11 is an idle state. The idle state is a steady state in which no load is applied to the engine 11, and the vehicle is stopped without the accelerator pedal 31 being stepped on while the engine 11 is operating.

  If the determination condition in step 100 is not satisfied (the engine is in the non-idle state), in step 800, the above-described map for determining the valve opening amount is used to set the engine operating state at that time (in this case, the intake pressure). A corresponding valve opening amount is obtained and set as the indicated valve opening amount.

  On the other hand, if the determination condition of step 100 is satisfied (idle state), the instruction valve opening amount to the PCV valve 42 is not used in step 200 without using the above-described map for determining the valve opening amount. The energization to the PCV valve 42 is controlled based on the indicated valve opening amount. By this control, the PCV valve 42 is forcibly opened to open the blow-by gas passage 41, and the blow-by gas in the crank chamber 37 is sucked into the intake passage 22 through the blow-by gas passage 41. If fuel is contained in the blow-by gas, the fuel in the blow-by gas is supplied to the combustion chamber 21 in addition to the fuel injected from the fuel injection valve 32. Due to the addition of fuel in the blowby gas, the air-fuel ratio becomes a richer value than the stoichiometric air-fuel ratio as compared with the case where there is no addition.

  Next, in step 300, when the PCV valve 42 is opened, the deviation amount (= | FAF−A |) of the feedback correction value FAF from the reference value A (“0”) is more than the predetermined value X (> 0). It is determined whether or not it has become larger. The predetermined value X is set based on a value (determined value: 35% described above) that diagnoses that the fuel supply system is abnormal when the deviation amount is larger than this value. Here, the predetermined value X is set to 30%, which is a value slightly closer to the reference value A (= 0) than the determination value. Specifically, in step 300, it is determined whether the feedback correction value FAF is less than a value (−30%) corresponding to the predetermined value X. In other words, it is determined whether or not the feedback correction value FAF is greatly deviated from the reference value A (= 0) to the minus side by a predetermined value X (“30%”).

  If this determination condition is not satisfied, there is no risk of a misdiagnosis, and the process proceeds to step 800 described above. On the other hand, if the determination condition of step 300 is satisfied, the valve opening of the PCV valve 42 is prohibited in step 400, that is, the instruction valve opening amount to the PCV valve 42 is set to “0”. The energization to the PCV valve 42 is controlled based on the amount. When the PCV valve 42 is closed by this control, the intake pressure (negative pressure) does not act on the crankcase 14 and the return of the blow-by gas to the intake passage 22 is stopped. Since the fuel in the blow-by gas does not flow into the combustion chamber 21, only the fuel injected from the fuel injection valve 32 is supplied to the combustion chamber 21. In this way, the recirculation amount of the blow-by gas is controlled (reduced) so that the feedback correction value FAF (deviation amount) does not become larger than the predetermined value X.

  If the deviation amount of the feedback correction value FAF with respect to the reference value A becomes smaller than the predetermined value X by this valve closing, the determination condition of the step 300 is satisfied because it is influenced by the fuel in the blow-by gas. Yes, it can be said that the fuel supply system is normal. On the other hand, if the deviation amount is still larger than the predetermined value X even when the PCV valve 42 is closed, it can be said that the determination condition of the step 300 is satisfied because the fuel supply system was originally abnormal. . For this reason, after the opening of the PCV valve 42 is prohibited in step 400, the diagnosis result of the fuel supply system performed by comparing the deviation amount with the predetermined value X becomes highly accurate.

  Next, in step 500, it is determined whether or not the engine 11 is operating in a predetermined operation region after the opening of the PCV valve 42 is prohibited (closed), that is, after the prohibition of the recirculation of blow-by gas is started. The predetermined operation area is an area where the deviation amount of the feedback correction value FAF from the reference value A is smaller than the predetermined value X (FAF deviation amount small area). In the present embodiment, the operation region other than the operation region operated in the idle state is set as the predetermined operation region. If the determination condition in step 500 is not satisfied, the process returns to step 300 described above. Therefore, until entering the predetermined operation range, that is, in the idle state, as long as the determination condition of step 300 is satisfied, the opening of the PCV valve 42 is prohibited (closed).

  On the other hand, if the determination condition in step 500 is satisfied, in step 600, the predetermined amount β (with respect to the valve opening amount corresponding to the engine operating state calculated using the map for determining the valve opening amount described above. > 0). Then, this addition result is set as an instruction valve opening amount to the PCV valve 42. Accordingly, the indicated valve opening amount in this case is larger than the amount corresponding to the engine operating state at that time (the amount during normal operation).

  When the instruction valve opening amount is calculated in step 600 or 800, in the next step 700, the PCV valve 42 is opened by controlling energization to the PCV valve 42 based on the calculated instruction valve opening amount. If the indicated valve opening amount is the one calculated in step 600, the engine 11 is operated in a predetermined operation region after the prohibition of the recirculation of blow-by gas is started (the FAF deviation amount is in a small region). The recirculation of blow-by gas will be resumed on the condition. Then, after the processing of step 700, a series of processing of this routine is finished.

In the above routine, the processing of steps 300 and 400 by the ECU 50 corresponds to the reflux control means, and the processing of step 200 corresponds to the valve opening means.
According to the first embodiment described in detail above, the following effects can be obtained.

  (1) When the recirculation amount of the blowby gas is changed, the magnitude of the influence of the fuel contained in the blowby gas on the concentration state of the air-fuel mixture changes. As a result, the amount of deviation of the feedback correction value FAF from the reference value A changes, and the diagnosis result may differ.

  In this respect, in the first embodiment, when the abnormality of the fuel supply system is diagnosed, the recirculation amount of the blow-by gas is set within a range in which the deviation amount of the feedback correction value FAF from the reference value A does not exceed the predetermined value X. It is set. This is because the limit value (allowable range) of the deviation amount of the feedback correction value FAF caused by blow-by gas is set, and the recirculation amount of the blow-by gas is changed in a range where the feedback correction value FAF is within this allowable range. It is synonymous. The limit value (allowable range) is a value (range) that the deviation amount of the feedback correction value FAF caused by blow-by gas can be taken under the condition that no erroneous diagnosis is caused. Therefore, by setting (changing) the recirculation amount within the above range, the influence of the fuel in the blow-by gas on the concentration state of the air-fuel mixture is reduced, and the result of the fuel supply system diagnosis performed based on the deviation amount It is possible to increase the accuracy of.

  (2) The predetermined operation condition of the engine 11 is that the deviation amount of the feedback correction value FAF from the reference value A is larger than the predetermined value X (step 300). When an abnormality of the fuel supply system is diagnosed, if this predetermined operating condition is satisfied (step 300: YES), the PCV valve 42 of the blow-by gas recirculation device is controlled so that the recirculation amount of the blow-by gas is reduced. (Step 400). By this reduction, the influence of the fuel in the blow-by gas on the concentration state of the air-fuel mixture (feedback correction value FAF) is reduced. If the deviation amount is equal to or less than the predetermined value X, the deviation amount is larger than the predetermined value X before the control is performed, but the deviation amount becomes smaller than the predetermined value X because the control is performed. Therefore, it can be said that the fuel supply system is normal. On the other hand, if the deviation amount is still larger than the predetermined value X even if the control is performed, it can be said that the fuel supply system is abnormal. Therefore, after reducing the recirculation amount by the control, the diagnosis result of the fuel supply system performed by comparing the deviation amount with the predetermined value X becomes highly accurate.

  (3) Although related to (2) above, particularly in this embodiment, the PCV valve 42 is closed to prohibit the recirculation amount of blow-by gas according to the establishment of a predetermined operating condition (step 300: YES) ( Step 400) realizes a reduction in the reflux amount. Then, by prohibiting the recirculation of the blow-by gas by this prohibition and preventing the fuel in the blow-by gas from flowing into the combustion chamber 21, the influence of the fuel on the concentration state of the air-fuel mixture is reduced or eliminated. I have to. Therefore, by comparing the amount of deviation of the feedback correction value FAF from the reference value A and the predetermined value X, it is possible to more accurately diagnose whether or not the fuel supply system is abnormal. It is possible to reliably suppress misdiagnosis even in situations where erroneous diagnosis results are likely to be generated.

  (4) If the diagnosis is stopped when the fuel concentration in the blow-by gas becomes high (Patent Document 1), the opportunity to diagnose the fuel supply system is reduced. In the present embodiment, since such a diagnosis stop is not performed, it is possible to avoid a decrease in the chances of diagnosis of the fuel supply system.

  (5) When the PCV valve 42 is opened in a region where the deviation amount of the feedback correction value FAF from the reference value A is large, blow-by gas is recirculated to the intake system, and the deviation amount is larger than the predetermined value X. Prone. In this regard, in this embodiment, the PCV valve is operated when the engine 11 is operated in an operation region in which the deviation amount of the feedback correction value FAF from the reference value A is large prior to the determination of success or failure of the predetermined operation condition (step 300). 42 is forcibly opened (steps 100 and 200). For this reason, by opening the PCV valve 42 in such an operation region, the deviation amount of the feedback correction value FAF from the reference value A is made larger than the predetermined value X, and a situation in which the predetermined operation condition is satisfied is surely created. be able to.

  (6) Assuming that the amount of fuel in the blow-by gas is substantially constant regardless of the operating state of the engine 11, the total amount of this fuel flowing into the combustion chamber 21 increases, and the fuel flows from the fuel injection valve 32. As the influence of the fuel on the fuel injection amount increases, the feedback correction value FAF also increases. Such a situation is when the basic injection amount is small in the above-described equation (ii), and is typically idle. In consideration of this point, in the present embodiment, the PCV valve 42 is forcibly opened during idling (steps 100 and 200). By opening the valve, the blow-by gas is recirculated, and a situation where the above operating condition is satisfied and the fuel supply system is diagnosed as abnormal can be reliably and efficiently created.

  (7) When the recirculation of the blow-by gas is prohibited (step 400), after adhering to the wall surface of the cylinder 12, it is scraped off by the sliding of the piston ring accompanying the reciprocating motion of the piston 17, and normally burns with the blow-by gas. The fuel returned to the chamber 21 is not discharged from the engine 11 and is mixed into the engine oil. This mixing dilutes the engine oil, lowers the viscosity, and lowers the lubricating performance.

  On the other hand, in the present embodiment, a region where the deviation amount of the feedback correction value FAF from the reference value A is smaller than the predetermined value X is set as a predetermined operation region, and the engine 11 is operated after the prohibition of the recirculation of blowby gas. The recirculation of the blow-by gas is resumed on the condition that it is operated in (Step 500). If the fuel supply system is normal, when the recirculation is resumed, the deviation from the reference value A of the feedback correction value FAF is smaller than the predetermined value X due to the recirculation prohibition performed before that. For this reason, there is little possibility that the fuel supply system is erroneously diagnosed due to the resumption of recirculation of blow-by gas. Therefore, the fuel in the blow-by gas that causes the oil to be diluted can be guided to the combustion chamber 21 and burned while suppressing erroneous diagnosis of the fuel supply system.

(8) When recirculation of blow-by gas is resumed, a value obtained by adding a predetermined amount β (> 0) to the valve opening amount corresponding to the operating state of the engine 11 at that time is set as the instruction valve opening amount to the PCV valve 42. (Step 600). By controlling the energization of the PCV valve 42 based on this instruction valve opening amount, the amount of blow-by gas recirculation is made larger than the amount corresponding to the engine operating state at that time. Therefore, the fuel in the blow-by gas retained in the crankcase 14 during the recirculation prohibition period can be quickly discharged from the engine 11 after resumption of recirculation, and the oil dilution by the fuel can be quickly eliminated.
(Second Embodiment)
Next, a second embodiment that embodies the present invention will be described with reference to FIGS. 4 and 5 with a focus on differences from the first embodiment. The difference in configuration of the second embodiment from the first embodiment is that the engine 11 is provided with two types of fuel injection valves, as shown in FIG. One fuel injection valve is a first fuel injection valve 51 that directly injects fuel into the combustion chamber 21 as in the first embodiment, and the other fuel injection valve injects fuel toward the intake port 22a. The second fuel injection valve 52 supplies fuel to the combustion chamber 21 through the intake passage 22. That is, the second fuel injection valve 52 is added to the first fuel injection valve 51 corresponding to the fuel injection valve 32 in the first embodiment. Then, fuel is injected from these first and second fuel injection valves 51 and 52 simultaneously or independently.

  In addition, the second embodiment is different from the first embodiment in that control is performed to suppress an increase in the fuel concentration in the blowby gas during the prohibition of recirculation of the blowby gas (step 400). It is to be. This is due to the following reason. The recirculation of the blow-by gas is prohibited when the predetermined operating condition is satisfied, that is, the deviation amount of the feedback correction value FAF representing the concentration state of the air-fuel mixture from the reference value A becomes larger than the predetermined value X. When you are. By this recirculation prohibition, normally (when the fuel supply system is normal), the deviation amount should be equal to or less than the predetermined value X, and the recirculation prohibition should be unnecessary. However, if a phenomenon that increases the concentration of fuel in the blow-by gas while prohibiting recirculation occurs, the deviation amount immediately exceeds the predetermined value X when recirculation is prohibited and recirculation is resumed. Therefore, it is necessary to prohibit the reflux of blow-by gas again.

  Such a phenomenon of increasing the fuel concentration is likely to occur when fuel is directly injected from the first fuel injection valve 51 into the combustion chamber 21. This is because the fuel spray injected from the first fuel injection valve 51 is likely to adhere to the wall surface of the cylinder 12, and this attached fuel is scraped off by the sliding of the piston ring accompanying the reciprocating motion of the piston 17. This is because the vehicle rides back to the combustion chamber 21 through the intake passage 22.

  Therefore, in the second embodiment, processing for suppressing an increase in the fuel concentration in the blow-by gas is performed. Specifically, in the routine of FIG. 3, after the processing of steps 100 to 400, the routine proceeds to step 410 of FIG. 5, and fuel injection from the first fuel injection valve 51, so-called in-cylinder injection, is prohibited. The process of step 410 by the ECU 50 corresponds to a concentration increase suppression means. Then, after the processing of step 410, the processing after step 500 in FIG. 3 is performed. The second fuel injection valve 52 is not subjected to such processing for prohibiting fuel injection.

Therefore, according to the second embodiment, in addition to the effects (1) to (8) in the first embodiment described above, the following effects can be obtained.
(9) When recirculation is prohibited (step 400), fuel injection from the first fuel injection valve 51 is prohibited (step 410). For this reason, the amount of fuel adhering to the wall surface of the cylinder 12 and thus the amount of fuel scraped off by the piston ring is reduced, and the progress of the increase in the fuel concentration in the blow-by gas is suppressed. It is possible to prevent the phenomenon that the deviation amount becomes larger than the predetermined value X immediately after the reflux of the blow-by gas is prohibited, and to prevent the reflux prohibition from being performed unnecessarily.

  (10) The second fuel injection valve 52 is not subjected to the process for prohibiting fuel injection. For this reason, even if the fuel injection from the first fuel injection valve 51 is stopped, the fuel injection from the second fuel injection valve 52 is continued to prevent the fuel from being supplied to the combustion chamber 21, and the minimum A limited amount of fuel can be secured. It is possible to avoid a problem that the fuel is excessively insufficient as the fuel injection of the first fuel injection valve 51 is stopped.

(Third embodiment)
Next, a third embodiment embodying the present invention will be described with reference to FIG. 6 with a focus on differences from the second embodiment. In the third embodiment, when recirculation is prohibited (step 400), instead of prohibiting fuel injection from the first fuel injection valve 51, the injection ratio of the first fuel injection valve 51 is made small. Yes. Here, the injection ratio of the first fuel injection valve 51 is the ratio of the injected fuel amount of the first fuel injection valve 51 to the both injected fuel amounts of the first and second fuel injection valves 51 and 52. For example, if the total amount of fuel injected from both fuel injection valves 51 and 52 is constant, the amount of fuel injected from the first fuel injection valve 51 is reduced, and the decrease is injected from the second fuel injection valve 52. By making up for the increase in the fuel amount, the injection ratio of the first fuel injection valve 51 is reduced. In order to reflect the change (decrease) in the injection ratio in the routine of FIG. 3, the process of step 420 in FIG. 6 is performed instead of step 410 in FIG. In step 420, the fuel injection ratio of the first fuel injection valve 51 is changed (decreased) to a value smaller than that before the recirculation is prohibited. The process of step 420 by the ECU 50 corresponds to a concentration increase suppression unit.

Therefore, according to the third embodiment, in addition to the same effects (1) to (9) as in the second embodiment, the following effects can be obtained.
(11) The amount of fuel injected from the first fuel injection valve 51 is decreased, and the decrease is compensated for by the increase in the amount of fuel injected from the second fuel injection valve 52. The amount of fuel injected from the first fuel injection valve 51 can be reduced without changing the amount of injected fuel (maintained constant).

Note that the present invention can be embodied in another embodiment described below.
A fixed value may be used as the predetermined amount β in step 600 of FIG. 3, or a variable value that changes according to conditions may be used.

-The addition process of predetermined amount (beta) may be abbreviate | omitted in step 600 of FIG. 3, and the valve opening amount according to the engine driving | running state calculated from the map is good also as instruction | indication valve opening amount.
-After the engine 11 is started, the vehicle is always in an idle state at a relatively early time regardless of the type of driving of the vehicle. Therefore, as the process of step 100 in FIG. 3, it may be determined whether or not “the engine is in the first idle state after the engine 11 is started”. By changing in this way, the effect of each said embodiment can be acquired reliably from the comparatively early time after the engine 11 start-up.

  If the predetermined condition is satisfied after the processing in step 700 in FIG. 3, the processing in steps 100 to 500 may be performed again. By doing so, the accuracy of abnormality diagnosis of the fuel supply system can be increased. Examples of the predetermined condition include “after the engine 11 has been warmed up and the vehicle has traveled a certain distance”. This is because the temperature of the engine oil (oil temperature) rises as the engine 11 warms up and the travel distance increases, and the amount of fuel that can dilute the engine oil increases. This is because the influence of the change on the feedback correction value FAF is reduced after waiting for the degree of change in the fuel amount to decrease.

  In the engine using two types of fuel injection valves (the first fuel injection valve 51 and the second fuel injection valve 52), the same control (see FIG. 3) as in the first embodiment is performed. Also good.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the structure about 1st Embodiment which actualized this invention. The schematic diagram which shows the structure of a blow-by gas recirculation apparatus. The flowchart which shows the procedure of the control which suppresses the misdiagnosis of the fuel supply system resulting from the recirculation | reflux of blowby gas. Schematic which shows the structure of the engine in 2nd Embodiment which actualized this invention. The flowchart which shows a different location from FIG. 3 regarding the procedure of the control which suppresses the misdiagnosis of a fuel supply system. The flowchart which shows a different location from FIG. 3 regarding the procedure of the control which suppresses the misdiagnosis of a fuel supply system in 3rd Embodiment which actualized this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 21 ... Combustion chamber, 22 ... Intake passage, 38 ... Blow-by gas recirculation device, 42 ... PCV valve (recirculation amount adjustment valve), 50 ... ECU (Recirculation control means, valve opening means, concentration increase) (Suppressing means), 51... First fuel injection valve, 52... Second fuel injection valve, FAF... Feedback correction value (parameter indicating the concentration state of the mixture), A.

Claims (10)

Used for an internal combustion engine that is provided with a blow-by gas recirculation device that recirculates blow-by gas to the intake system and that diagnoses an abnormality in the fuel supply system based on an amount of deviation from a reference value of a parameter that represents the concentration state of the air-fuel mixture in the combustion chamber It can be
The blow-by gas recirculation device includes a recirculation amount adjusting valve for adjusting a recirculation amount of the blow-by gas,
The recirculation amount of the blow-by gas is set according to the engine operating state at that time, and when the fuel supply system is diagnosed, the blow-by gas is within a range in which the deviation amount of the parameter from the reference value does not exceed a predetermined value. Reflux control means for setting the reflux amount ;
Prior to diagnosis of the fuel supply system, valve opening for forcibly opening the recirculation amount adjustment valve when the internal combustion engine is operated in a predetermined operation region in which the deviation amount of the parameter from the reference value is large and means,
The recirculation control means that has set the recirculation amount reduces the recirculation amount of the blow-by gas, assuming that a predetermined operating condition is satisfied when a deviation amount of the parameter from the reference value is larger than a predetermined value. And controlling the blow-by gas recirculation device. 2. The control device for an internal combustion engine according to claim 1, wherein the parameter is a feedback correction value used in feedback control of a fuel injection amount so that the air-fuel ratio of the air-fuel mixture converges to a stoichiometric air-fuel ratio. 3. The control device for an internal combustion engine according to claim 1, wherein when the internal combustion engine is in an idle state, the valve opening means opens the recirculation amount adjustment valve on the assumption that the internal combustion engine is operating in the predetermined operation region. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the recirculation control means prohibits recirculation of blow-by gas by the blow-by gas recirculation apparatus in response to establishment of the predetermined operating condition. The recirculation control means restarts recirculation of the blowby gas on condition that the internal combustion engine is operated in an operation region other than the predetermined operation region after the prohibition of recirculation of the blowby gas is started. Control device for internal combustion engine. 6. The control device for an internal combustion engine according to claim 5, wherein the operation region other than the predetermined operation region is a region in which a deviation amount of the parameter from a reference value is smaller than the predetermined value. The said recirculation | reflux control means controls the said blowby gas recirculation apparatus so that the recirculation | reflux amount of blowby gas may become larger than the amount according to the engine operating state at the time of the recirculation | reflux resumption. Control device for internal combustion engine. 5. The control apparatus for an internal combustion engine according to claim 4, further comprising concentration increase suppression means for suppressing an increase in fuel concentration in the blowby gas while the recirculation control means prohibits recirculation. The internal combustion engine includes a first fuel injection valve that directly injects fuel into the combustion chamber and a second fuel injection valve that injects fuel into the combustion chamber through an intake passage as the fuel supply system,
  9. The control device for an internal combustion engine according to claim 8, wherein the concentration increase suppression unit prohibits fuel injection from the first fuel injection valve while the recirculation control unit prohibits recirculation. The internal combustion engine includes a first fuel injection valve that directly injects fuel into the combustion chamber and a second fuel injection valve that injects fuel into the combustion chamber through an intake passage as the fuel supply system,
  The concentration increase suppression means is a ratio of the injected fuel amount of the first fuel injection valve to the injected fuel amounts of the first fuel injection valve and the second fuel injection valve during the recirculation prohibition by the recirculation control means. The control apparatus for an internal combustion engine according to claim 8, wherein the injection ratio is reduced.

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