JP2010133387A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for internal combustion engine whose accuracy of feedback control can be improved as compared to the conventional one in an internal combustion engine where fuel is injected into a cylinder and an intake air passage. <P>SOLUTION: An ECU of the engine practices the following steps of: obtaining a fundamental injection amount dividing rate for distributing fuel to an in-cylinder injector and a port injector based on an engine loading factor and an engine revolution speed (step S21); calculating an injection amount dividing rate at the time of the next fuel injection based on fuel pressure (step S22); and calculating a difference Δ between the fundamental injection amount dividing rate and the injection amount dividing rate at the next fuel injection (step S23). As a result, when the difference Δ of the injection amount dividing rate is larger than a threshold (Yes at step S24), making a learning inhibiting flag ON to interrupt the learning in PI feedback control (step S25); and when the difference Δ of the injection amount dividing rate is equal to or smaller than a threshold (No at step S24), the learning inhibiting flag is made OFF to practice the learning in the PI feedback control (step S26). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine capable of injecting fuel into a combustion chamber and an intake passage.

  Conventionally, a vehicle driven by an internal combustion engine has an exhaust purification catalyst and an air-fuel ratio sensor in the exhaust passage of the internal combustion engine, and the detection result detected by the air-fuel ratio sensor is improved so that the exhaust purification performance of the exhaust purification catalyst is enhanced. Based on this, a control device is mounted to bring the air-fuel ratio of the internal combustion engine closer to the stoichiometric air-fuel ratio.

  As this type of control device, an air-fuel ratio sensor is provided upstream of the exhaust purification catalyst, and an air-fuel ratio feedback control is performed according to the oxygen concentration of the exhaust gas detected by the air-fuel ratio sensor ( For example, see Patent Document 1).

  The conventional control device described in Patent Document 1 executes feedback control for correcting the injection amount of fuel supplied into the combustion chamber of the internal combustion engine in accordance with the oxygen concentration of the exhaust gas detected by the air-fuel ratio sensor. Thus, the actual air-fuel ratio is controlled to approach the stoichiometric air-fuel ratio. Further, the conventional control device learns a correction value for the injection amount, and executes feedback control to correct the injection amount with the learned correction value, thereby improving the followability of the actual air-fuel ratio with respect to the theoretical air-fuel ratio. It was.

  Further, the conventional control device described in Patent Document 1 includes an in-cylinder injector that injects fuel into a combustion chamber of an internal combustion engine, and an in-port injection that injects fuel into an intake port connected to the combustion chamber. And the injection amount in the in-port injector and the in-cylinder injector are corrected based on the engine load factor and the engine speed of the internal combustion engine. It was.

In this conventional control device, when the fuel injection amount calculated for the in-port injector and the in-cylinder injector is less than the minimum injection amount that can be injected by these injectors, the calculated fuel A minimum injection amount of fuel is injected instead of the injection amount. At this time, since more fuel than the calculated fuel injection amount is injected and the actual air-fuel ratio fluctuates to the rich side, the conventional control device interrupts the execution of learning in the feedback control, and the accuracy of the feedback control deteriorates. It was supposed to prevent.
JP 2007-32328 A

  However, the conventional control device for an internal combustion engine as described above does not take into account the control for varying the distribution ratio of the fuel amount supplied to the in-port injector and the in-cylinder injector. It was. For this reason, even if the air-fuel ratio fluctuates due to the change in the fuel amount distribution ratio, the learning is continued. As a result, the accuracy of the feedback control may be deteriorated.

  The present invention has been made to solve such a problem, and provides an internal combustion engine control apparatus capable of improving the accuracy of feedback control in an internal combustion engine in which fuel is injected into a cylinder and an intake passage as compared with the conventional one. The purpose is to provide.

  In order to achieve the above object, the control apparatus for an internal combustion engine according to the present invention (1) injects fuel into a first injection means for injecting fuel into a combustion chamber of the internal combustion engine and an intake passage connected to the combustion chamber. A fuel amount for calculating a total fuel amount to be supplied to the first injection unit and the second injection unit, based on the second injection unit that performs, the amount of air sucked into the combustion chamber, and the engine speed Calculated by a calculating means, an actual air-fuel ratio calculating means provided in an exhaust passage connected to the internal combustion engine, and calculating an actual air-fuel ratio in the combustion chamber based on an exhaust component, and calculated by the actual air-fuel ratio calculating means Control means for correcting the total fuel amount calculated by the fuel amount calculation means so as to match the actual air-fuel ratio with a predetermined air-fuel ratio, and executing feedback control for learning the correction amount in the correction; A control device for an internal combustion engine comprising the first injection unit and the total fuel amount corrected by the control unit based on at least an engine load factor and an engine speed required for the internal combustion engine A distribution calculation means for calculating a ratio to be distributed to the second injection means, and a first threshold value in which a fuel amount corresponding to the ratio to be distributed to the first injection means calculated by the distribution calculation means is predetermined. If the ratio is less than, the fuel amount corresponding to the proportion distributed to the first injection means is set as the first threshold value, and the first amount is calculated from the fuel amount corresponding to the proportion distributed to the second injection means. A distribution correction unit that corrects a distribution ratio so as to subtract a difference between a threshold value and a fuel amount corresponding to a ratio distributed to the first injection unit calculated by the distribution calculation unit, and the distribution correction unit corrects the distribution ratio. Distribution Determination means for determining whether or not a difference between the ratio and the distribution ratio calculated by the distribution calculation means exceeds a predetermined second threshold, and the control means includes the distribution correction If the determination means determines that the difference between the distribution ratio corrected by the means and the distribution ratio calculated by the distribution calculation means exceeds the second threshold, the second threshold The learning is interrupted until it is determined by the determination means as below.

  With this configuration, in an internal combustion engine in which fuel is injected into the cylinder and the intake passage, the ratio of distributing the fuel to the first injection means and the second injection means is corrected, and the actual air-fuel ratio may vary. Is high, the learning in the feedback control is interrupted, so that the temporary fluctuation of the actual air-fuel ratio can be prevented from affecting the learning, and the accuracy of the feedback control can be improved as compared with the conventional one.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can improve the precision of feedback control in the internal combustion engine in which a fuel is injected in a cylinder and an intake passage can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram schematically showing a vehicle equipped with an internal combustion engine control apparatus according to an embodiment of the present invention. In the present embodiment, the case where the vehicle is equipped with a four-cylinder engine will be described.

  As shown in FIG. 1, an engine 2 constituting the internal combustion engine of the present invention is mounted on a vehicle and includes four cylinders 6. In addition, the cylinder 6 which concerns on this Embodiment comprises the combustion chamber of the internal combustion engine which concerns on this invention. These cylinders 6 are respectively connected to an intake manifold 4, and the intake manifold 4 is connected to a common surge tank 5.

  The surge tank 5 is connected to an intake pipe 10, and an air cleaner 12, an air flow meter 11, and a throttle valve 14 are disposed in the intake pipe 10.

  The throttle valve 14 is driven by an electric motor 13 and its opening degree is controlled in accordance with a signal output from an engine ECU (Electronic Control Unit) 8 described later.

  Further, each cylinder 6 is connected to an exhaust manifold 15, and this exhaust manifold 15 is connected to an exhaust pipe 16. A three-way catalytic converter 17 and an air-fuel ratio sensor 42 are installed in the exhaust pipe 16.

  Each cylinder 6 is provided with an in-cylinder injector 19 for injecting fuel into the cylinder. Further, the intake manifold 4 constituting a part of the intake passage is provided with a port injection injector 20 for injecting fuel into the intake passage. Here, the in-cylinder injector 19 constitutes a first injection means for injecting fuel into the combustion chamber according to the present invention, and the port injector 20 injects fuel into the intake passage according to the present invention. The 2nd injection means for doing is constituted.

  The fuel injection amount and the injection timing by the in-cylinder injector 19 and the port injector 20 are controlled by the engine ECU 8. Further, as will be described later, the engine ECU 8 controls the injection ratio of the fuel injection amount in the injectors 19 and 20.

  The in-cylinder injector 19 is connected to a common fuel distribution pipe 21, and high pressure fuel is pumped to the fuel distribution pipe 21 from a high pressure fuel pump 23 driven by the power of the engine 2. ing. A check valve 22 is installed between the fuel distribution pipe 21 and the high-pressure fuel pump 23 to prevent back flow of fuel from the fuel distribution pipe 21 side to the high-pressure fuel pump 23 side.

  An electromagnetic spill valve 24 is installed in parallel with the high-pressure fuel pump 23, and the discharge side of the high-pressure fuel pump 23 is connected to the suction side via the electromagnetic spill valve 24. The opening degree of the electromagnetic spill valve 24 is controlled by the engine ECU 8. The smaller the opening degree, the larger the amount of fuel supplied from the high-pressure fuel pump 23 to the fuel distribution pipe 21. When fully opened, the fuel supply from the high-pressure fuel pump 23 to the fuel distribution pipe 21 is stopped.

  The port injection injector 20 is connected to a fuel distribution pipe 25 for low pressure. Both the fuel distribution pipe 25 and the high-pressure fuel pump 23 are connected to a low-pressure fuel pump 27 via a fuel pressure regulator 26.

  The low-pressure fuel pump 27 sucks fuel stored in the fuel tank 29 via the fuel filter 28 and pumps it to the fuel pressure regulator 26. The fuel pressure regulator 26 returns a part of the fuel discharged from the low pressure fuel pump 27 to the fuel tank 29 when the pressure of the fuel discharged from the low pressure fuel pump 27, that is, the fuel pressure becomes higher than a predetermined set value. Thus, the fuel pressure supplied to the port injector 20 is controlled to be equal to or lower than this set value.

  The engine ECU 8 includes a CPU (Central Processing Unit) 34, a RAM (Random Access Memory) 33, a ROM (Read Only Memory) 32, an input port 35, an output port 36, and the like that are connected to each other via a bidirectional bus 31. It is comprised by the microcomputer provided with. The CPU 34 performs output control of the engine 2 by performing signal processing according to a program stored in the ROM 32 in advance while using the temporary storage function of the RAM 33. The signal output from the output port 36 is transmitted to an actuator (not shown) or the like via the A / D converter 47.

  As will be described later, the engine ECU 8 constitutes an internal combustion engine control device, fuel amount calculation means, distribution calculation means, actual air-fuel ratio calculation means, control means, determination means, and distribution correction means according to the present invention.

  The engine ECU 8 is connected to the air flow meter 11, the water temperature sensor 38, the fuel pressure sensor 40, the air-fuel ratio sensor 42, the accelerator opening sensor 44, and the rotation speed sensor 46, and inputs signals output from these sensors. Input is made via the port 35.

  The air flow meter 11 measures the amount of air sucked into the intake pipe 10 and outputs a voltage corresponding to the amount of intake air as an output signal. The output signal of the air flow meter 11 is A / D converted. It is input to the input port 35 via the device 37.

  The fuel pressure sensor 40 is installed in the fuel distribution pipe 21 and outputs a voltage corresponding to the fuel pressure in the fuel distribution pipe 21 as an output signal. This output signal is output from the A / D converter 41. To the input port 35.

  The air-fuel ratio sensor 42 is constituted by a linear air-fuel ratio sensor that outputs, as an output signal, a voltage corresponding to the oxygen concentration of the exhaust gas and the concentration of the unburned component of the fuel in the exhaust pipe 16. The signal representing the fuel ratio is input to the input port 35 via the A / D converter 43. Therefore, the air-fuel ratio sensor 42 and the engine ECU 8 constitute the actual air-fuel ratio calculating means according to the present invention.

  The water temperature sensor 38 is installed in the engine 2 and outputs a voltage corresponding to the cooling water temperature of the engine 2 as an output signal. This output signal is an A / D converter 39 as a signal indicating the engine cooling water temperature. To the input port 35.

  The accelerator opening sensor 44 outputs a voltage corresponding to the amount of depression of the accelerator pedal 18 as an output signal, and this output signal is input to the input port 35 via the A / D converter 45. .

  The rotational speed sensor 46 generates a pulse as an output signal at every predetermined rotational angle of a timing rotor (not shown) installed on the crankshaft of the engine 2 and inputs the pulse to the input port 35 as a signal representing the engine rotational speed. It has become.

  The ROM 32 of the engine ECU 8 stores a fuel injection amount map in which the intake air amount and the engine speed are associated with the total fuel amount supplied to the in-cylinder injector 19 and the port injector 20. Yes. When the engine ECU 8 obtains a signal representing the intake air amount from the air flow meter 11 and a signal representing the engine speed from the rotational speed sensor 46, the engine ECU 8 refers to the fuel injection amount map, and the in-cylinder injector 19 and the port The total amount of fuel supplied to the injector 20 for injection is calculated.

  Therefore, the engine ECU 8 according to the present embodiment calculates the total amount of fuel supplied to the in-cylinder injector 19 and the port injector 20 based on the intake air amount and the engine speed according to the present invention. A quantity calculating means is configured.

  Further, the ROM 32 stores a correction map for correcting the total fuel amount calculated from the fuel injection amount map in accordance with the engine coolant temperature. The fuel amount corrected in accordance with the correction map is totaled. It may be the amount of fuel.

  Further, the engine ECU 8 calculates a deviation between the actual air-fuel ratio input from the air-fuel ratio sensor 42 and the target air-fuel ratio stored in the ROM 32 so that the deviation between the actual air-fuel ratio and the target air-fuel ratio approaches zero. Feedback control is executed. Further, the engine ECU 8 calculates a learning value by integrating the calculated deviation for a predetermined time, and stores it in the RAM 33.

  That is, the engine ECU 8 according to the present embodiment executes PI feedback control that calculates the proportional term and the integral term as the learning value from the actual air-fuel ratio and the target air-fuel ratio and performs feedback control. The engine ECU 8 may further calculate a differential term based on the actual air-fuel ratio and the target air-fuel ratio, and execute PID feedback control using the proportional term, the integral term, and the differential term.

  Therefore, the engine ECU 8 according to the present embodiment corrects the total fuel amount based on the calculated actual air-fuel ratio so that the actual air-fuel ratio matches a predetermined target air-fuel ratio, and the correction amount in the correction. The control means which performs feedback control which learns as learning value is comprised.

  In this PI feedback control, the engine ECU 8 calculates the fuel correction amount dQ as follows, and corrects the fuel injection amount at the next fuel injection by the fuel correction amount dQ.

dQ = Qp + Qi (1)
Here, Qp is a proportional term and Qi is an integral term.

The proportional term Qp is calculated as follows.
Qp = Kp · ΔQ (2)
Here, Kp is a proportional gain. ΔQ is the difference between the amount of fuel for setting the actual air-fuel ratio to the target air-fuel ratio and the current amount of fuel burned in the cylinder 6. The amount of fuel burned in the cylinder 6 is calculated by dividing the detected value of the intake air amount by the detected value of the air-fuel ratio.

The integral term Qi is calculated as follows.
Qi = Qi + Ki.ΔQ (3)
Here, Ki is an integral gain.

  As will be described later, when the learning prohibition flag stored in the RAM 33 is ON, the engine ECU 8 interrupts the update of the learning value until the learning prohibition flag is turned OFF. In this case, the integral term Qi in PI feedback control is calculated by the following equation.

Qi = Qi (3 ')
Therefore, when the update of the learning value is prohibited, the integral term Qi becomes equal to the previous value.
Here, the fuel distribution process for the in-cylinder injector 19 and the port injector 20 will be described.

The engine ECU 8 corrects the total fuel amount calculated by the fuel injection amount map with the fuel correction amount dQ calculated by the above equation (1), and calculates the required injection amount Qall. The calculated required injection amount Qall is distributed to the in-cylinder injector 19 and the port injector 20 at a predetermined injection ratio. The injection ratio is stored in the ROM 32 as a basic injection ratio map associated with the engine load ratio and the engine speed. Further, the engine load factor is calculated based on the accelerator opening and the engine speed output by the accelerator opening sensor 44 and the rotation speed sensor 46.
Therefore, the engine ECU 8 according to the present embodiment constitutes a distribution calculation unit according to the present invention.

FIG. 2 is a diagram showing a basic injection ratio map according to the embodiment of the present invention.
In the basic injection ratio map, a region where the engine speed is high is defined as a direct injection region, and in this region, fuel is injected only from the in-cylinder injector 19. Further, the region where the engine speed is lower than the direct injection region is defined as the direct injection and port injection region. As is well known, the in-cylinder injector 19 contributes to an increase in output performance, and the port injector 20 contributes to the uniformity of the air-fuel mixture. Therefore, the two types of injectors 19 and 20 having different characteristics as described above are selectively used according to the engine speed and the engine load factor, thereby realizing improvement in fuel consumption and acceleration.

  By the way, as indicated by an arrow 51 in FIG. 2, the running state of the vehicle starts from a high load region 52 where the fuel pressure in the fuel distribution pipe 21 is high and the fuel injection amount is large, and the fuel pressure in the fuel distribution pipe 21 is low. May shift to a light load region 53 having a small size. However, when the state transition indicated by the arrow 51 is performed in a short time, the decrease in the fuel pressure in the fuel distribution pipe 21 may be delayed from this state transition. In a state where the fuel pressure is not sufficiently lowered, as will be described below, the accuracy of control of the fuel injection amount by the in-cylinder injector 19 is lowered. For this reason, the engine ECU 8 executes control for correcting the injection ratio.

  FIG. 3 is a diagram showing the injection accuracy of the in-cylinder injector 19 according to the embodiment of the present invention. FIG. 4 is a diagram showing a minimum injection amount map 55 according to the embodiment of the present invention.

  As shown in FIG. 3, when the in-cylinder injector 19 is energized by the engine ECU 8, fuel is injected into the cylinder 6 with an injection amount Q proportional to the energization time. Therefore, the engine ECU 8 can accurately adjust the injection amount Q of the fuel injected into the cylinder 6 by controlling the energization time for the in-cylinder injector 19.

  However, if the energization time of the in-cylinder injector 19 becomes too short, the energization time and the injection amount Q are not proportional to each other due to friction when a needle valve (not shown) is lifted, and the fuel from the engine ECU 8 is not proportional. The accuracy of the injection amount Q decreases. That is, the in-cylinder injector 19 has a minimum injection amount Qmin that can execute accurate fuel injection with respect to the energization time.

  The minimum injection amount Qmin at which the energization time and the injection amount Q are not proportional to each other varies depending on the fuel pressure of the fuel supplied to the in-cylinder injector 19. Specifically, as shown in FIG. 3, the minimum injection amount Qmin at the time of high fuel pressure is larger than the minimum injection amount Qmin at the time of low fuel pressure.

  Therefore, as shown in FIG. 4, the engine ECU 8 stores in the ROM 32 a minimum injection amount map 55 in which the fuel pressure of the fuel supplied to the in-cylinder injector 19 is associated with the minimum injection amount Qmin. The minimum injection amount map 55 is determined so that the minimum injection amount Qmin at the high fuel pressure is larger than the minimum injection amount Qmin at the low fuel pressure.

  If the fuel amount for the in-cylinder injector 19 calculated based on a predetermined injection ratio is less than the minimum injection amount Qmin, the engine ECU 8 reduces the fuel amount for the in-cylinder injector 19 to the minimum. The injection amount Qmin is maintained, and the difference between the injection amount acquired from the basic injection distribution rate map and the minimum injection amount Qmin is reduced from the fuel amount injected by the port injector 20. That is, the engine ECU 8 does not change the total required injection amount Qall supplied to the in-cylinder injector 19 and the port injector 20, and the injection ratio for the in-cylinder injector 19 and the port injector 20 is divided. Is to be corrected.

  Therefore, the engine ECU 8 according to the present embodiment constitutes a distribution correction unit according to the present invention. Further, the minimum injection amount Qmin according to the present embodiment means a fuel amount that represents the first threshold value according to the present invention.

  FIG. 5 is a flowchart for explaining the fuel distribution processing according to the embodiment of the present invention. The following processing is executed at predetermined time intervals by the CPU 34 constituting the engine ECU 8, and a program that can be processed by the CPU 34 is realized. Here, the predetermined time interval means a constant rotation of the crankshaft of the engine 2.

  First, the engine ECU 8 calculates the total required injection amount Qall using the total fuel amount calculated by the fuel injection amount map and the fuel correction amount dQ calculated by the above equation (1) (step S11). . In this case, the engine ECU 8 refers to the engine learning prohibition flag stored in the RAM 33, and when the learning prohibition flag is OFF, substitutes the value of Qi calculated by the above equation (3) into the equation (1). When the learning prohibition flag is ON, the value of Qi calculated by the above equation (3 ′) is substituted into equation (1).

  Next, the engine ECU 8 calculates a basic injection division ratio (step S12). The basic injection ratio is the ratio of the amount of fuel distributed to the in-cylinder injector 19 and the port injector 20 as described above, and is 2 associated with the engine speed and the engine load factor of the engine 2. It is stored in advance in the ROM 32 as a basic dimensional ejection ratio map.

  Next, the engine ECU 8 calculates a basic direct injection amount Qdb (step S13). This basic direct injection amount Qdb is the product of the total required injection amount Qall calculated in step S11 and the ratio of the fuel amount distributed to the in-cylinder injector 19 at the basic injection distribution ratio calculated in step S12. Is required.

  Next, the engine ECU 8 calculates a basic port injection amount Qpb (step S14). This basic direct injection amount Qpb is the product of the total required injection amount Qall calculated in step S11 and the ratio of the fuel amount distributed to the port injector 20 at the basic injection distribution ratio calculated in step S12. Desired.

  Next, the engine ECU 8 calculates a minimum injection amount Qmin for the in-cylinder injector 19 (step S15). Specifically, when the engine ECU 8 acquires a signal representing the fuel pressure in the fuel distribution pipe 21 from the fuel pressure sensor 40, the engine ECU 8 refers to the minimum injection amount map 55 stored in the ROM 32 and calculates the minimum injection amount Qmin. .

  Next, the engine ECU 8 compares the basic direct injection amount Qdb calculated in step S13 with the minimum injection amount Qmin calculated in step S15 (step S16).

  If the engine ECU 8 determines that the basic direct injection amount Qdb is equal to or greater than the minimum injection amount Qmin as a result of the comparison (Yes in step S16), the basic direct injection amount Qdb is set as the final direct injection amount Qd (step S16). S17) In the next fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  Then, the engine ECU 8 sets the basic port injection amount Qpb calculated in step S14 as the final port injection amount Qp (step S18), and the amount of fuel injected from the port injector 20 in the next fuel injection is the final direct injection amount. The port injection injector 20 is controlled so as to be the injection amount Qd.

  On the other hand, when the engine ECU 8 determines in step S16 that the basic direct injection amount Qdb is less than the minimum injection amount Qmin (No in step S16), the minimum injection amount Qmin is set as the final direct injection amount Qd (step S19). In the next fuel injection, the in-cylinder injector 19 is controlled so that the amount of fuel injected from the in-cylinder injector 19 becomes the final direct injection amount Qd.

  Then, the engine ECU 8 sets the value obtained by subtracting the difference between the minimum injection amount Qmin and the basic direct injection amount Qdb from the basic port injection amount Qpb calculated in step S14 as the final port injection amount Qp (step S20). In this fuel injection, the port injector 20 is controlled so that the fuel amount injected from the port injector 20 becomes the final port injection amount Qp.

  Hereinafter, a characteristic configuration of engine ECU 8 constituting the control device for an internal combustion engine according to the embodiment of the present invention will be described with reference to FIG.

  When the minimum injection amount Qmin is the final direct injection amount Qd, the engine ECU 8 constituting the control device of the engine 2 determines the ratio of the final direct injection amount Qd and the final port injection amount Qp at this time next time. It is calculated as an injection distribution ratio at the time of fuel injection.

  Further, the engine ECU 8 determines the injection ratio at the time of the next fuel injection calculated from the basic injection ratio calculated by the basic injection ratio map and the ratio between the final direct injection quantity Qd and the final port injection quantity Qp ( Hereinafter, a difference Δ with respect to the next injection division ratio is calculated, and it is determined whether or not the difference Δ exceeds a predetermined threshold value. Therefore, the engine ECU 8 according to the present embodiment constitutes a determination unit according to the present invention. Further, this threshold means the second threshold according to the present invention.

  As the predetermined threshold, the actual air-fuel ratio fluctuates in accordance with fluctuations in the injection ratio, so that the integral term Qi as the learning value in the feedback control is affected by the fluctuations. It is a value that can prevent the phenomenon that the exhaust gas purification performance by the three-way catalytic converter 17 is deteriorated as a result of deviation from the air-fuel ratio, and is obtained beforehand by experimental measurement.

Further, when the engine ECU 8 determines that the difference Δ between the previous injection ratio and the next injection ratio exceeds a predetermined threshold value, the actual air-fuel ratio fluctuation value is added to the feedback control learning value. In order to prevent the actual air-fuel ratio from deviating from the target air-fuel ratio in the subsequent feedback control and the exhaust gas purification performance of the three-way catalytic converter 17 from being deteriorated, the integral term Qi is updated as a learning value. Is supposed to be interrupted.
The engine ECU 8 continues to interrupt the update of the integral term Qi until the difference Δ between the previous injection division ratio and the next injection division ratio becomes equal to or less than a predetermined threshold value.

  FIG. 6 is a flowchart for explaining the learning restriction process according to the embodiment of the present invention. The following processing is executed by the CPU 34 constituting the engine ECU 8 and realizes a program that can be processed by the CPU 34. Further, the following process is started from the time when step S18 or step S20 in the fuel distribution process described above is completed, and is executed at the time interval every time step S18 or step S20 is completed in this fuel distribution process. It has become.

  First, the engine ECU 8 acquires a basic injection division ratio (step S21). Specifically, the engine ECU 8 stores the basic injection ratio in the RAM 33 when the basic injection ratio is calculated from the basic injection ratio map in step S12 (see FIG. 5) described above. The basic injection ratio stored in the RAM 33 is acquired.

  Next, the engine ECU 8 calculates the next injection division ratio (step S22). Specifically, the engine ECU 8 acquires the final direct injection amount Qd and the final port injection amount Qp, and calculates the ratio thereof. The engine ECU 8 stores these values in the RAM 33 when calculating the final direct injection amount Qd and the final port injection amount Qp as described above, and calculates the next injection division rate in this step. At this time, the value stored in the RAM 33 is acquired.

  Next, the engine ECU 8 calculates a difference Δ between the basic injection ratio acquired in step S21 and the next injection ratio calculated in step S22 (step S23). As a method for calculating the difference Δ, for example, the difference in the ratio of the fuel amount distribution to one of the injectors in the basic injection ratio and the next injection ratio is obtained.

  Next, the engine ECU 8 determines whether or not the calculated difference Δ in the injection ratio is larger than a predetermined threshold value (step S24). The predetermined threshold value is stored in the ROM 32 as described above, and the engine ECU 8 acquires this value and compares it with the calculated difference Δ of the injection ratio.

  When the engine ECU 8 determines that the difference Δ in the injection ratio is larger than the threshold (Yes in step S24), the engine ECU 8 turns on the learning prohibition flag (step S25). Specifically, the engine ECU 8 turns on an engine learning prohibition flag stored in the RAM 33.

  In this case, when calculating the fuel correction amount dQ in the PI feedback control described above, the engine ECU 8 calculates the integral term Qi using the equation (3 ′) instead of the equation (3), and calculates the calculated integral term. Substitute Qi into equation (1).

  On the other hand, when the engine ECU 8 determines that the difference Δ in the injection ratio is equal to or less than the threshold value (No in step S24), the engine ECU 8 turns off the learning prohibition flag (step S25).

  In this case, when calculating the fuel correction amount dQ in the above-described PI feedback control, the engine ECU 8 calculates the integral term Qi using the equation (3), and the calculated integral term Qi into the equation (1). substitute.

  As described above, in the control apparatus for an internal combustion engine according to the embodiment of the present invention, in-cylinder injector 19 and port injector 20 in engine 2 in which fuel is injected into cylinder 6 and into the intake passage. When the ratio of fuel distribution is corrected and the actual air-fuel ratio is likely to fluctuate, learning in feedback control is interrupted, preventing temporary fluctuations in the actual air-fuel ratio from affecting learning. The accuracy of the feedback control can be improved as compared with the conventional one.

  In the above description, the engine ECU 8 has described the case where the minimum injection amount Qmin is set based on the fuel pressure in the fuel distribution pipe 21, but the present invention is not limited to this, and the minimum injection amount Qmin depends on the fuel pressure and fuel. It may be determined based on temperature. In this case, the minimum injection amount Qmin is increased as the fuel temperature is higher, and the minimum injection amount Qmin is decreased as the fuel temperature is lower.

  As described above, the control device for an internal combustion engine according to the present invention has an effect that the accuracy of feedback control can be improved over the conventional one in an internal combustion engine in which fuel is injected into the cylinder and the intake passage, This is useful for a control device for an internal combustion engine that corrects the distribution of fuel injected into the cylinder and the intake passage.

1 is a schematic configuration diagram schematically showing a vehicle equipped with an internal combustion engine control device according to an embodiment of the present invention. It is a figure which shows the basic injection division ratio map which concerns on embodiment of this invention. It is a figure which shows the injection precision of the injector for cylinder injection which concerns on embodiment of this invention. It is a figure which shows the minimum injection amount map which concerns on embodiment of this invention. It is a flowchart for demonstrating the fuel distribution process which concerns on embodiment of this invention. It is a flowchart for demonstrating the learning restriction | limiting process which concerns on embodiment of this invention.

Explanation of symbols

2 Engine (Internal combustion engine)
4 intake manifold 5 surge tank 6 cylinder 8 engine ECU (control device for internal combustion engine, fuel amount calculation means, distribution calculation means, actual air-fuel ratio calculation means, control means, determination means, distribution correction means)
DESCRIPTION OF SYMBOLS 10 Intake pipe 11 Air flow meter 12 Air cleaner 13 Electric motor 14 Throttle valve 15 Exhaust manifold 16 Exhaust pipe 17 Three-way catalytic converter 18 Accelerator pedal 19 In-cylinder injector (first injection means)
20 port injector (second injection means)
21 Fuel distribution pipe 23 High pressure fuel pump 25 Fuel distribution pipe 26 Fuel pressure regulator 27 Low pressure fuel pump 28 Fuel filter 29 Fuel tank 31 Bidirectional bus 32 ROM
33 RAM
34 CPU
38 Water temperature sensor 40 Fuel pressure sensor 42 Air-fuel ratio sensor (actual air-fuel ratio calculation means)
44 Accelerator opening sensor 46 Rotation speed sensor (fuel amount calculation means, distribution calculation means)

Claims (1)

First injection means for injecting fuel into the combustion chamber of the internal combustion engine;
Second injection means for injecting fuel into an intake passage connected to the combustion chamber;
Fuel amount calculating means for calculating a total fuel amount supplied to the first injection means and the second injection means based on the amount of air sucked into the combustion chamber and the engine speed;
An actual air-fuel ratio calculating means which is provided in an exhaust passage connected to the internal combustion engine and calculates an actual air-fuel ratio in the combustion chamber based on a component of exhaust;
The total fuel amount calculated by the fuel amount calculating means is corrected so that the actual air fuel ratio calculated by the actual air fuel ratio calculating means matches a predetermined air fuel ratio, and the correction amount in the correction is learned. A control means for executing feedback control, and a control device for an internal combustion engine comprising:
A ratio of distributing the total fuel amount corrected by the control means to the first injection means and the second injection means based on at least the engine load factor and the engine speed required for the internal combustion engine. A distribution calculating means for calculating;
When the amount of fuel corresponding to the ratio of distribution to the first injection means calculated by the distribution calculation means falls below a predetermined first threshold, the ratio to be distributed to the first injection means The corresponding fuel amount is set as the first threshold value, and is distributed to the first injection means calculated by the first threshold value and the distribution calculating means from the fuel amount corresponding to the proportion to be distributed to the second injection means. Distribution correction means for correcting the distribution ratio so as to subtract the difference from the fuel amount corresponding to the ratio to be performed;
Determining means for determining whether a difference between the distribution ratio corrected by the distribution correcting means and the distribution ratio calculated by the distribution calculating means exceeds a predetermined second threshold; Prepared,
The control means determines that the difference between the distribution ratio corrected by the distribution correction means and the distribution ratio calculated by the distribution calculation means exceeds the second threshold value by the determination means. In some cases, the learning is interrupted until the determination means determines that the value is equal to or less than the second threshold value.