JP4470832B2 - Control device for internal combustion engine - Google Patents

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 that includes both a port injector and a cylinder injector.

  There is known an internal combustion engine that includes both a port injector that injects fuel into an intake port and an in-cylinder injector that injects fuel into the cylinder. In JP-A-5-2321221, in such an internal combustion engine, in order to accurately control the air-fuel ratio, the amount of fuel injected from the port injector adheres to the inner wall of the intake port or adheres to the inner wall of the intake port. A system that corrects the injection amount of the in-cylinder injector in consideration of the amount of fuel flowing into the cylinder is disclosed.

JP-A-5-2321221 Japanese Patent No. 2754744

  However, in the above conventional air-fuel ratio control technology, the air-fuel ratio cannot be controlled with sufficient accuracy in practice, and as a result, there are cases where the exhaust emission and drivability are adversely affected. The cause is considered to be insufficient consideration for a phenomenon peculiar to the internal combustion engine provided with both the port injector and the in-cylinder injector.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine that can accurately control an air-fuel ratio in an internal combustion engine that includes both a port injector and an in-cylinder injector. The purpose is to provide.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
Blow-back fuel amount estimation means for estimating the amount of fuel contained in the blow-back of intake air from the cylinder to the intake port based on a predetermined parameter;
Based on the amount estimated by the blowback fuel amount estimating means, the amount of blowback correction for correcting the error due to blowback is included, and the port injection amount injected from the port injector and the cylinder injection injected from the cylinder injector An injection amount calculating means for calculating an injection amount;
With
The predetermined parameter includes an injection ratio of the port injector and the in-cylinder injector,
The blow-back fuel amount estimation means estimates that the blow-back fuel amount is smaller when the injection ratio of the in-cylinder injector is large than when it is small .

A second invention is an internal combustion engine control apparatus for achieving the above object,
A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
Blow-back fuel amount estimation means for estimating the amount of fuel contained in the blow-back of intake air from the cylinder to the intake port based on a predetermined parameter;
Based on the amount estimated by the blowback fuel amount estimating means, the amount of blowback correction for correcting the error due to blowback is included, and the port injection amount injected from the port injector and the cylinder injection injected from the cylinder injector An injection amount calculating means for calculating an injection amount;
With
The predetermined parameter includes an injection start time of the in-cylinder injector,
The blowback fuel amount estimation means estimates that the blowback fuel amount is smaller when the injection start timing of the in-cylinder injector is late than when it is early .

The third invention is the first or second invention, wherein
The injection amount calculation means includes means for distributing the blow-back correction amount into both the port injection amount and the in-cylinder injection amount and calculating.

Moreover, 4th invention is 1st or 2nd invention,
The injection amount calculating means includes means for calculating the blowback correction amount only in the in-cylinder injection amount.

The fifth invention is the fourth invention, wherein
When the blow-back correction amount is included only in the in-cylinder injection amount, an injection timing control means is further provided which sets the injection start timing of the in-cylinder injector to a timing after the intake valve is closed.

The sixth invention is the fourth or fifth invention, wherein
The injection amount calculation means calculates the blow-back correction amount when the change in the blow-back correction amount of the current cycle relative to the blow-back correction amount of the previous cycle is larger than a determination value when the blow-back correction amount is included in only the in-cylinder injection amount. Including a partial counting means for counting only a part of the amount into the in-cylinder injection amount.

The seventh invention is the sixth invention, wherein
An amount corresponding to the remainder of the blowback correction when the blowback correction is a positive value and only a part of the blowback correction is included in the in-cylinder injection amount by the partial calculation means. The exhaust stroke injection means for injecting the fuel from the in-cylinder injector in the exhaust stroke is further provided.

The eighth invention is the sixth or seventh invention, wherein
When the blowback correction amount is a negative value and only a part of the blowback correction amount is included in the in-cylinder injection amount by the partial calculation means, the remaining portion of the blowback correction amount is set to the next cycle or later. It is further characterized by further comprising an injection amount reducing means for reducing the injection amount after the next cycle by being included in the injection amount.

  According to the first aspect of the invention, when calculating the fuel injection amount in the internal combustion engine having both the port injector and the in-cylinder injector, it is possible to correct an error due to the influence of the intake air blowback. Further, the amount of blown fuel as a basis for the blowback correction can be estimated while reflecting the influence of the injection ratio between the port injector and the in-cylinder injector. For this reason, under various operating conditions, the amount of blown-back fuel, and hence the amount of correction for blow-back, can be obtained with high accuracy. For this reason, according to the present invention, the air-fuel ratio in the internal combustion engine can be accurately controlled.

  According to the second invention, when calculating the fuel injection amount in the internal combustion engine including both the port injector and the in-cylinder injector, it is possible to correct the error due to the influence of the intake air blowback. In addition, the amount of blowback fuel that is the basis for the blowback correction can be estimated while reflecting the influence of the injection start timing of the in-cylinder injector. For this reason, under various operating conditions, the amount of blown-back fuel, and hence the amount of correction for blow-back, can be obtained with high accuracy. For this reason, according to the present invention, the air-fuel ratio in the internal combustion engine can be accurately controlled.

  According to the third invention, since the blowback correction amount is included in both the port injection amount and the in-cylinder injection amount, the ratio between the port injection amount and the in-cylinder injection amount is the same as before the calculation of the blowback correction amount. Can not be. For this reason, according to the present invention, the injection ratio of the port injector and the in-cylinder injector can be easily and accurately controlled to the target value.

  According to the fourth aspect of the present invention, it is possible to delay the calculation timing of the blowback fuel amount and approach the time when the intake valve is closed when the actual blowback amount is determined. For this reason, according to the present invention, the amount of blown-back fuel, and hence the amount of blow-back correction, can be obtained with higher accuracy. As a result, the air-fuel ratio can be controlled with higher accuracy.

  According to the fifth aspect, it is possible to delay the calculation timing of the blowback fuel amount to the vicinity of the time when the intake valve is closed when the actual blowback amount is determined. For this reason, according to the present invention, the amount of blown-back fuel, and hence the amount of blow-back correction, can be obtained with particularly high accuracy. As a result, the air-fuel ratio can be controlled with particularly high accuracy.

  According to the sixth aspect of the invention, it is possible to reliably avoid the occurrence of torque shock due to the inclusion of the blowback correction.

  According to the seventh invention, when only a part of the blowback correction amount is included in the fuel injection amount in order to avoid a torque shock, the exhaust air / fuel ratio shift due to the remaining portion not being included is recovered. Can do. For this reason, according to the present invention, it becomes easy to keep a good balance of the catalyst oxygen storage amount.

  According to the eighth aspect of the invention, when only a part of the blowback correction amount is included in the fuel injection amount in order to avoid a torque shock, the exhaust air / fuel ratio shift caused by the fact that the remainder is not included is recovered. Can do. For this reason, according to the present invention, it becomes easy to keep a good balance of the catalyst oxygen storage amount.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 6. The internal combustion engine 6 is a multi-cylinder engine having a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders. Each cylinder of the internal combustion engine 6 is provided with a piston 8, a combustion chamber 10, an intake valve 12, an exhaust valve 14, a spark plug 16, and an intake port 18 and an exhaust port 20 that communicate with the inside of the cylinder. It has been. The intake valve 12 opens and closes so that the combustion chamber 10 and the intake port 18 are in a conduction state or a cutoff state. The exhaust valve 14 opens and closes so that the combustion chamber 10 and the exhaust port 20 are in a conductive state or a shut-off state.

  For each cylinder of the internal combustion engine 6, a port injector 22 for injecting fuel into the intake port 18 and an in-cylinder injector 24 for directly injecting fuel into the cylinder (inside the combustion chamber 10) are provided. It has been. Fuel pressurized by a pump (not shown) is sent to the port injector 22 and the in-cylinder injector 24, respectively. In the internal combustion engine 6, fuel can be supplied from both the port injector 22 and the in-cylinder injector 24 to each cylinder.

  The intake port 18 communicates with the intake passage 30. An air cleaner 32 is provided at the upstream end of the intake passage 30, and air is taken into the intake passage 30 via the air cleaner 32. An air flow meter 33 is disposed downstream of the air cleaner 32. The air flow meter 33 is a sensor that detects an intake air amount GA flowing in the intake passage 30. A downstream portion of the intake passage 30 is branched for each cylinder (for each intake port 18), and a surge tank 34 is provided at the branched portion. A throttle valve 36 is disposed upstream of the surge tank 34 in the intake passage 30. The throttle valve 36 is provided with a throttle position sensor 37 for detecting the opening degree. An intake pressure sensor 38 that detects the intake pipe pressure PM is provided downstream of the throttle valve 36.

  Connected to the exhaust port 20 is an exhaust passage 40 for discharging the combustion gas generated by the combustion in the combustion chamber 10 as an exhaust gas. A catalyst 42 for purifying exhaust gas is provided in the exhaust passage 40. An air-fuel ratio sensor 44 for detecting the air-fuel ratio of the exhaust gas is disposed upstream of the catalyst 42 in the exhaust passage 40.

  A crank angle sensor 46 is installed in the vicinity of the crankshaft 45 of the internal combustion engine 6. The crank angle sensor 46 is a sensor that reverses the Hi output and the Lo output each time the crankshaft 45 rotates by a predetermined rotation angle. According to the output of the crank angle sensor 46, it is possible to detect the rotational position and rotational speed of the crankshaft 45, and further the engine rotational speed NE and the like. The internal combustion engine 6 further includes a water temperature sensor 48 that detects the cooling water temperature TW.

  The intake valve 12 of the internal combustion engine 6 is driven by a variable valve mechanism 50. The variable valve mechanism 50 can open and close the intake valve 12 in synchronization with the rotation of the crankshaft 45 and change the valve timing VT and the valve lift amount VL. A sensor 52 that detects the state of the variable valve mechanism 50 is provided in the vicinity of the variable valve mechanism 50. According to the output of the sensor 52, the actual values of the valve timing VT and the valve lift amount VL of the intake valve 12 can be detected.

  The system of this embodiment includes an ECU (Electronic Control Unit) 60. The ECU 60 is connected to various sensors such as the air flow meter 33 and the air-fuel ratio sensor 44 described above, and various actuators such as the port injector 22, the in-cylinder injector 24, and the variable valve mechanism 50 described above. The ECU 60 can control the operating state of the internal combustion engine 6 by appropriately driving each actuator based on the output of each sensor.

[Fuel behavior model]
2 and 3 are diagrams for explaining the fuel behavior model used in the present embodiment. This fuel behavior model is a model representing the behavior of fuel after being injected from the port injector 22 and the in-cylinder injector 24.

  It is considered that part of the fuel injected from the port injector 22 adheres to the inner wall of the intake port 18 and the outside of the intake valve 12, and the remaining part is sucked into the cylinder. In this model, as shown in FIG. 2, the amount of fuel injected from the port injector 22 is defined as a port injection amount fip, and fuel adhering to the inner wall of the intake port 18 (hereinafter referred to as “port adhering fuel”). Is the port attachment amount fwp, and the total amount of fuel adhering to the intake valve 12 (hereinafter referred to as “intake valve attachment fuel”) is the intake valve attachment amount fwv. In FIG. 2, the port attachment amount fwp and the intake valve attachment amount fwv are drawn together in one place, but actually the port attachment fuel and the intake valve attachment fuel are attached together in one place. Not exclusively.

  On the other hand, it is considered that a part of the fuel injected from the in-cylinder injector 24 adheres to the cylinder inner wall or the inner wall of the combustion chamber 10 and the remaining part is vaporized to contribute to combustion. In this model, as shown in FIG. 2, the amount of fuel injected from the in-cylinder injector 24 is defined as in-cylinder injection amount fid, and the fuel adhering to the inner wall of the cylinder or the combustion chamber 10 (hereinafter referred to as “in-cylinder”). The total amount of “attached fuel” is referred to as in-cylinder attached amount fwc. In FIG. 2, the in-cylinder adhesion amount fwc is drawn in one place, but actually, the in-cylinder attached fuel is not necessarily attached in one place.

  In FIG. 3, fcp represents the amount of fuel sucked into the cylinder from the intake port 18 (hereinafter referred to as “cylinder fuel intake amount”). Hereinafter, a method of calculating the in-cylinder fuel intake amount fcp in this model will be described with reference to FIG.

  In this model, the proportion of the fuel injected from the port injector 22 that adheres to the inner wall of the intake port 18 is defined as “port adhesion rate Rp”, and the proportion that adheres to the intake valve 12 is defined as “intake valve adhesion rate Rv”. It is defined as According to this definition, of the port injection amount fip, the amount added to the port-attached fuel without being sucked into the cylinder is represented by “Rp · fip”. Of the port injection amount fip, the amount added to the fuel adhering to the intake valve without being sucked into the cylinder is represented by “Rv · fip”. On the other hand, of the port injection amount fip, the amount that is directly injected into the cylinder after being injected is represented by “(1-Rp-Rv) · fip”.

  In addition to the amount represented by the above equation (1-Rp-Rv) · fip, the fuel vapor in the cylinder and the vaporization of the fuel adhering to the intake valve are added to the in-cylinder fuel intake amount fcp. The In this model, the proportion of the fuel adhering to the port at the start of the current cycle (before the intake valve 12 is opened) that remains attached without being sucked into the cylinder in the current cycle is defined as “port residual ratio Pp”. To do. According to this definition, the amount of fuel represented by “(1-Pp) · fwp” is sucked into the cylinder as the vaporized fuel attached to the port in this cycle. On the other hand, of the port adhesion amount fwp, the amount represented by “Pp · fwp” remains as it is after the end of the current cycle. Similarly, in the present model, the ratio of the fuel adhering to the intake valve that was present at the start of the current cycle and remaining adhering without being sucked into the cylinder in the current cycle is defined as “intake valve residual rate Pv”. According to this definition, the amount of fuel represented by “(1-Pv) · fwv” is sucked into the cylinder as the vaporization of the fuel adhering to the intake valve in this cycle. On the other hand, of the intake valve attachment amount fwv, the amount represented by “Pv · fwv” remains as it is after the end of this cycle.

  The above-described port adhesion rate Rp, intake valve adhesion rate Rv, port residual rate Pp, intake valve residual rate Pv, in-cylinder adhesion rate Rc, and in-cylinder residual rate Pc described later depend on the operating state of the internal combustion engine 6. Have different characteristics. In addition, according to this model, the above-described port adhesion amount fwp, intake valve adhesion amount fwv, and in-cylinder adhesion amount fwc are each increased or decreased by new adhesion, and the internal combustion engine 6 is rotated by one cycle. It changes every time it moves. Therefore, in the following, when those values are expressed in the k-th cycle, (k) is added after the symbols. The initial values fwp (0), fwc (0), and fwc (0) of the port attachment amount fwp, the intake valve attachment amount fwv, and the in-cylinder attachment amount fwc are all zero.

  From the above, the in-cylinder fuel intake amount fcp (k) in the k-th cycle can be expressed as the following equation (1). Further, the port adhesion amount fwp (k + 1) and the intake valve adhesion amount fwv (k + 1) at the end of the k-th cycle, that is, at the start of the k + 1-th cycle, are expressed by the following equations (2) and (3), respectively. ).

  On the other hand, fcd in FIG. 3 represents the amount of fuel that vaporizes in the cylinder and contributes to combustion (hereinafter referred to as “in-cylinder fuel vaporization amount”). Hereinafter, a method of calculating the in-cylinder fuel vaporization amount fcd in this model will be described with reference to FIG.

  In this model, the ratio of the fuel injected from the in-cylinder injector 24 that adheres to the inner wall of the cylinder and the inner wall of the combustion chamber 10 is defined as “in-cylinder adhesion rate Rc”. According to this definition, of the in-cylinder injection amount fid, the amount added to the in-cylinder attached fuel without being vaporized is represented by “Rc · fid”. On the other hand, of the in-cylinder injection amount fid, the amount that is directly vaporized after injection is represented by “(1-Rc) · fid”.

  The in-cylinder fuel vaporization amount fcd is added with the vaporization amount of the in-cylinder attached fuel in addition to the amount represented by the above equation (1-Rc) · fid. In this model, the ratio of the in-cylinder adhering fuel at the start of the current cycle that remains adhering without being vaporized in the current cycle is defined as “in-cylinder residual ratio Pc”. According to this definition, the amount of fuel represented by “(1-Pc) · fwc” corresponds to the vaporized portion of the in-cylinder attached fuel in the current cycle. On the other hand, of the in-cylinder adhesion amount fwc, the amount represented by “Pc · fwc” remains as it is after the end of the current cycle.

  From the above, the in-cylinder fuel vaporization amount fcd (k) in the k-th cycle can be expressed as the following equation (4). Further, the in-cylinder adhesion amount fwc (k + 1) after the end of the k-th cycle, that is, at the start of the k + 1-th cycle can be expressed as the following equation (5).

  Hereinafter, in the k-th cycle, the amount of fuel that can contribute to combustion in the cylinder (hereinafter referred to as “combustion contributing fuel amount”) is represented as fc (k). The combustion contribution fuel amount fc (k) in the k-th cycle is considered to be the sum of the in-cylinder fuel intake amount fcp (k) and the in-cylinder fuel vaporization amount fcd (k) according to the fuel behavior model described above. Therefore, it can be expressed as the following formula (6).

[Estimation of blown fuel amount fb]
According to the above-described fuel behavior model, it is possible to take into account the amount of injected fuel adhering to the wall surface and the amount of vaporized fuel adhering to the wall surface. Therefore, the fuel injection amount can be calculated with high accuracy in realizing the desired air-fuel ratio. In the present embodiment, in order to further improve the accuracy, correction for the amount of intake blow-back is added to such a fuel behavior model.

  Here, the return of intake air means that fresh air once sucked into the cylinder flows back to the intake port 18 before the intake valve 12 is closed. In general, in an internal combustion engine, the intake valve 12 is closed after passing through the bottom dead center for reasons such as effectively using intake inertia to increase intake efficiency. For this reason, when the piston 8 starts to rise after the intake bottom dead center and the intake valve 12 is not yet closed, a back flow of fresh air from the cylinder to the intake port 18 can occur.

  As the intake air blows back, the fuel contained therein is also returned from the cylinder to the intake port 18. Hereinafter, the fuel contained in the blow-back of the intake air is referred to as “blow-back fuel”. In addition, the amount of blown-back fuel is referred to as “blow-back fuel amount” and is represented by the symbol fb. In the present embodiment, the blowback fuel amount fb is estimated, and an error due to the influence of the blowback of the intake air is corrected based on the estimated value. In the internal combustion engine 6 including both the port injector 22 and the in-cylinder injector 24 as in the present embodiment, the fuel blown back from the port injector 22 and the fuel injected from the in-cylinder injector 24 are used as blowback fuel. And any of these may be included.

  The blowback fuel amount fb changes according to the operating state of the internal combustion engine 6. More specifically, the blowback fuel amount fb is the engine speed NE of the internal combustion engine 6, the load factor KL (or the intake pipe pressure PM), the valve timing VT and the valve lift amount VL of the intake valve 12, and the port It changes in accordance with a parameter such as a total injection amount fi that is a sum of the injection amount fip and the in-cylinder injection amount fid. For example, as the total injection amount fi increases, the blowback fuel amount fb increases. Further, the larger the valve lift amount VL of the intake valve 12, the greater the blowback fuel amount fb. Accordingly, in order to always accurately estimate the blowback fuel amount fb in various operating states, it is necessary to calculate the blowback fuel amount fb according to the values of these parameters.

  Therefore, in this embodiment, the dependency of the blowback fuel amount fb on each of the engine speed NE, the load factor KL, the valve timing VT, the valve lift amount VL, and the total injection amount fi is grasped in advance, and these dependencies are determined. Is stored in the ECU 60. Then, the ECU 60 calculates the blowback fuel amount fb by reflecting these dependencies. This makes it possible to accurately estimate the blowback fuel amount fb under various operating conditions.

  By the way, in the system of the present embodiment, the fuel injection start timing (hereinafter referred to as “in-cylinder injection start timing”) TD of the in-cylinder injector 24 is not fixed and is optimal according to the operating state of the internal combustion engine 6. It is adjusted to become. FIG. 4 is a graph showing the relationship between the blowback fuel amount fb and the in-cylinder injection start timing TD under the condition where other parameters are constant. As shown in FIG. 4, in the internal combustion engine 6 of the present embodiment, the blowback fuel amount fb also depends on the in-cylinder injection start timing TD. The reason is as follows.

  As described above, the blown-back fuel can include the amount injected from the port injector 22 and the amount injected from the in-cylinder injector 24. On the other hand, when the injection period of the in-cylinder injector 24 crosses the intake valve closing time, the fuel injected after the intake valve closing time does not return to the intake port 18 due to the blow back. For this reason, as shown in FIG. 4, when the period overlapping the intake valve opening period of the injection period of the in-cylinder injector 24 becomes shorter, the intake port 18 of the in-cylinder injection amount fid is proportional to this. The amount that blows back is reduced. When the in-cylinder injection start timing TD is after the intake valve closing time, the amount of in-cylinder injection amount fid that blows back to the intake port 18 becomes zero, and the entire in-cylinder injection amount fid remains in the cylinder. Therefore, in FIG. 4, in the range where the in-cylinder injection start timing TD is after the intake valve closing time, the blowback fuel amount fb is only the amount injected from the port injector 22, and thus takes a constant value. .

  In this way, the blowback fuel amount fb decreases as the in-cylinder injection start timing TD is delayed when other parameters are constant. In the present embodiment, when the blowback fuel amount fb is estimated, the in-cylinder injection start timing TD is added to the parameter that is the basis of the estimation of the blowback fuel amount fb in order to reflect such a tendency. Thereby, in this embodiment, the blowback fuel amount fb can be estimated with higher accuracy.

  In the present embodiment, the blowback fuel amount fb also depends on the injection ratio between the port injector 22 and the in-cylinder injector 24. In the present embodiment, the injection ratio γ is used to represent this injection ratio. The injection division ratio γ is a ratio of the port injection amount fip when the sum of the port injection amount fip and the in-cylinder injection amount fid is 1. That is, port injection amount fip: in-cylinder injection amount fid = γ: (1−γ). In the system according to the present embodiment, the injection ratio γ is not fixed and is adjusted to be optimal according to the operating state of the internal combustion engine 6.

  FIG. 5 is a graph showing the relationship between the blown back fuel amount fb and the injection ratio γ under the condition where other parameters are constant. As described above, of the fuel injected from the in-cylinder injector 24, the fuel injected after the intake valve is closed does not return to the intake port 18 due to blow-back. That is, it can be said that the fuel injected from the in-cylinder injector 24 is less likely to blow back than the fuel injected from the port injector 22. For this reason, as shown in FIG. 5, the higher the ratio of in-cylinder injection, in other words, the closer the injection ratio γ is to 0, the smaller the amount of blowback fuel fb.

  Therefore, in the present embodiment, when the blowback fuel amount fb is estimated, in order to reflect such a tendency, the injection ratio γ is added to the parameter that is the basis of the estimation of the blowback fuel amount fb. Thereby, in this embodiment, the blowback fuel amount fb can be estimated with higher accuracy.

[Calculation of port injection amount fip and in-cylinder injection amount fid]
Next, a method for calculating the port injection amount fip and the in-cylinder injection amount fid necessary for realizing a desired air-fuel ratio based on the above-described model will be described.

  In this embodiment, in order to calculate the port injection amount fip and the in-cylinder injection amount fid with better accuracy, the influence of the in-cylinder residual gas is taken into consideration. In an internal combustion engine, it is generally difficult to exhaust burned gas completely from the cylinder, so a part of the burned gas remains in the cylinder until the next cycle. Hereinafter, the amount of fuel (whether burned or unburned) contained in the gas remaining in the cylinder at the end of the k-th cycle, that is, at the start of the (k + 1) -th cycle, is expressed as “cylinder residual fuel amount fr (k ) ".

  Hereinafter, the amount of blown fuel in the k-th cycle is represented as fb (k). Further, the amount of fuel (whether burned or unburned) contained in the exhaust gas sent to the exhaust port 20 by the operation of the k-th cycle is represented as “exhaust fuel amount fex (k)”. This fex (k) can be accurately calculated by adding a correction for the influence of the blowback and a correction for the influence of the in-cylinder residual gas to the above-described combustion contributing fuel amount fc (k). That is, the discharged fuel amount fex (k) in the k-th cycle can be expressed as the following equation (7).

The term -fb (k) on the right side of the above equation (7) means that the amount blown back in the current cycle is subtracted. The term + fb (k−1) means that the amount blown back in the previous cycle is added by being sucked in the current cycle. The term -fr (k) means that the amount remaining in the cylinder and not discharged in this cycle is subtracted. The term + fr (k-1) means that the amount remaining in the cylinder from the previous cycle is added by being discharged in the current cycle.
The second to third lines on the right side of the above expression (7) are obtained by substituting the above expression (6) into fc (k) on the first line on the right side.

Hereinafter, the injection ratio in the k-th cycle is expressed as γ (k). Thus, the following equation (8) is established from the definition of the spray distribution ratio γ.
Further, if the target air-fuel ratio in the k-th cycle is α (k) and the amount of air sucked into the cylinder in the k-th cycle (hereinafter referred to as “cylinder intake air amount”) is m (k), the target The condition required for realizing the air-fuel ratio α (k) can be expressed by the following equation (9).

  The following equations (10) and (11) are obtained by substituting the above equations (8) and (9) into the above equation (7) and solving for fip (k) and fid (k), respectively.

  In the present embodiment, the port injection amount fip and the in-cylinder injection amount fid are calculated based on the above equations (10) and (11). In the present embodiment, the amount represented by the term including fb (k) and fb (k−1) in the above equations (10) and (11) is the amount of correction for blowback for correcting the error due to blowback. Equivalent to. In the present embodiment, by calculating the port injection amount fip and the in-cylinder injection amount fid by adding the blowback correction amount, it is possible to accurately correct the air-fuel ratio error (deviation) due to the effect of the blowback. The target air-fuel ratio α (k) can be realized with high accuracy.

[Specific Processing in Embodiment 1]
FIG. 6 shows a flowchart of a routine executed by the ECU 60 in the present embodiment in order to realize the above-described functions. This routine is executed separately for each cylinder of the internal combustion engine 6. This routine is executed every time the target cylinder operates for one cycle.

  According to the routine shown in FIG. 6, first, various parameters representing the current state of the internal combustion engine 6 are acquired (step 100). Specifically, here, the engine speed NE, load factor KL, valve timing VT, valve lift amount VL, total injection amount fi, in-cylinder intake air amount m, intake pipe pressure PM, cooling water temperature TW, etc. A physical quantity representing the six operating states is obtained by measurement or by a known calculation. Here, the load factor KL is a ratio between the intake air amount obtained when the throttle valve 36 is fully opened and the actual intake air amount GA, and can be calculated based on the output of the air flow meter 33 or the like. Further, the in-cylinder intake air amount m can be calculated based on the output of the air flow meter 33 or the output of the intake pressure sensor 38.

  In another routine, the ECU 60 sequentially sets the target air-fuel ratio α based on the operating state of the internal combustion engine 6 and the like. In the process of step 100, the total injection amount fi is calculated based on the target air-fuel ratio α and the cylinder intake air amount m. The total injection amount fi calculated in this way is not the actual injection amount, but is approximately used as a basis for calculating the blowback fuel amount fb in the processing of step 108 described later in the routine shown in FIG. It is what

  In the routine shown in FIG. 6, next, processing for calculating the port adhesion rate Rp, the intake valve adhesion rate Rv, the in-cylinder adhesion rate Rc, the port residual rate Pp, the intake valve residual rate Pv, and the in-cylinder residual rate Pc is executed. (Step 102). The ECU 60 stores a map in which these values are determined in relation to various parameters representing the state of the internal combustion engine 6 (for example, engine speed NE, load factor KL, valve timing VT, cooling water temperature TW, etc.). Yes. Here, a value corresponding to the current operating state is calculated with reference to the map.

  Next, a process for calculating a target in-cylinder injection start timing TD is performed (step 104). The ECU 60 stores a map that defines the optimum in-cylinder injection start timing TD in relation to various parameters that indicate the state of the internal combustion engine 6. Here, the in-cylinder injection start timing TD suitable for the current operating state is set as a target by referring to the map.

  Next, a process for calculating a target injection ratio γ is performed (step 106). The ECU 60 stores a map in which the optimal injection ratio γ is determined in relation to various parameters representing the state of the internal combustion engine 6. Here, by referring to the map, the injection ratio γ suitable for the current operating state is set as a target.

  Next, the process for calculating the blowback fuel amount fb is performed as follows (step 108). The ECU 60 stores a predetermined reference blowback fuel amount. Further, the ECU 60 has a plurality of parameters affecting the blowback fuel amount fb, such as engine speed NE, load factor KL, valve timing VT, valve lift amount VL, total injection amount fi, in-cylinder injection start timing TD, and injection division. For each rate γ, a map that defines correction coefficients for reflecting the influence of the rate γ is stored. The ECU 60 obtains correction coefficients for each parameter with reference to those maps, and calculates the blowback fuel amount fb by multiplying all the correction coefficients by the reference blowback fuel amount.

  In the processing of step 108, a map that can reflect the tendency as shown in FIG. 4 in the fuel amount fb is used as the map that defines the correction coefficient for the in-cylinder injection start timing TD. As a result, the influence of the difference in the in-cylinder injection start timing TD can be accurately factored in, so that the blowback fuel amount fb that matches the actual value can be obtained.

  Further, in the processing of step 108, a map that can reflect the tendency as shown in FIG. 5 in the blowback fuel amount fb is used as the map that defines the correction coefficient for the injection ratio γ. As a result, the influence of the difference in the injection ratio γ can be accurately factored in, so that the blow-back fuel amount fb that matches the actual value can be obtained.

  In the routine shown in FIG. 6, next, a process of calculating the in-cylinder residual fuel amount fr is performed (step 110). The ECU 60 stores a map in which the value of the in-cylinder residual fuel amount fr is determined in relation to various parameters representing the state of the internal combustion engine 6. Here, a value corresponding to the current operating state is calculated with reference to the map.

  Next, processing for calculating the port injection amount fip and the in-cylinder injection amount fid is performed as follows (step 112). The ECU 60 stores the above equations (10) and (11). The ECU 60 substitutes the values calculated in steps 102 to 110 of the current processing cycle and the values calculated in step 110 of the previous processing cycle into these equations. Further, the ECU 60 substitutes the value of the blowback fuel amount fb calculated in step 118 described later at the time of the previous processing cycle as “fb (k−1)” in the above expressions (10) and (11). . Further, the ECU 60 substitutes the values at the previous processing cycle of the port attachment amount fwp, the intake valve attachment amount fwv, and the in-cylinder attachment amount fwc calculated in step 114, which will be described later, into the above equations (10) and (11). To do. By such processing, the port injection amount fip and the in-cylinder injection amount fid can be calculated.

  Note that the ECU 60 sets a port injection timing suitable for the current operating state in another routine. Fuel corresponding to the port injection amount fip calculated in step 112 is injected from the port injector 22 in accordance with the port injection timing. Further, in accordance with the in-cylinder injection start timing TD calculated in step 104, fuel corresponding to the in-cylinder injection amount fid calculated in step 112 is injected from the in-cylinder injector 24.

  In the routine shown in FIG. 6, next, a process of calculating the port adhesion amount fwp, the intake valve adhesion amount fwv, and the in-cylinder adhesion amount fwc is performed (step 114). The ECU 60 stores the above equations (2), (3), and (5). The ECU 60 substitutes the port adhesion amount fwp, the intake valve adhesion amount fwv, and the in-cylinder adhesion amount fwc obtained in the previous processing cycle together with the values calculated in the above-described steps 102 and 108 of the current processing cycle. By doing so, the port adhesion amount fwp, the intake valve adhesion amount fwv, and the in-cylinder adhesion amount fwc can be updated to the latest values. The updated values of the port adhesion amount fwp, the intake valve adhesion amount fwv, and the in-cylinder adhesion amount fwc are used for calculating the blowback fuel amount fb in the next processing cycle (step 108).

  In the routine shown in FIG. 6, it is next determined whether or not the intake valve 12 of the target cylinder is closed (step 116). This determination is made based on the rotational position of the crankshaft 45 detected by the crank angle sensor 46, the valve timing VT detected by the sensor 52, and the like.

  After it is determined in step 116 that the intake valve 12 is closed, a process of calculating the blowback fuel amount fb again based on the latest information is performed (step 118). The recalculated fuel amount fb recalculated here is used as fb (k-1) when calculating the port injection amount fip and the in-cylinder injection amount fid in the next processing cycle as described above. It is done.

  The reason why the blowback fuel amount fb is recalculated in step 118 is as follows. Since the intake air blowback occurs when the intake valve 12 is open, the actual blowback amount is determined at the moment when the intake valve 12 is closed. Therefore, the blowback fuel amount fb calculated when the intake valve is closed is closer to the actual value. Therefore, the port injection amount fip and the in-cylinder injection amount fid can be calculated with higher accuracy by using the blowback fuel amount fb recalculated when the intake valve is closed as fb (k-1) in the next processing cycle. Can do.

  As described above, according to the routine shown in FIG. 6, the blowback fuel amount fb is accurately estimated by reflecting the influence of the in-cylinder injection start time TD and the influence of the injection ratio γ on the blowback fuel amount fb. be able to. Then, by calculating the blowback correction amount based on the blowback fuel amount fb in the calculation of the port injection amount fip and the in-cylinder injection amount fid, the actual air-fuel ratio is accurately adjusted to the target air-fuel ratio α under various operating conditions. It can be controlled well.

  Further, in the present embodiment, as can be seen from the above equations (10) and (11), the blow-back correction amount is distributed and included in both the port injection amount fip and the in-cylinder injection amount fid. As a result, the port injection amount fip and the in-cylinder injection amount fid can be calculated so as to satisfy the target injection ratio γ. For this reason, the actual injection ratio γ can be controlled easily and accurately.

  By the way, in the above-described first embodiment, the intake valve 12 is waited for closing (step 116), and the blowback fuel amount fb is recalculated (step 118). The processing does not have to be performed. That is, the blowback fuel amount fb calculated in step 108 may be used as “fb (k−1)” in step 112 of the next processing cycle.

  In the first embodiment described above, both the in-cylinder injection start timing TD and the injection ratio γ are included in the basic parameters for estimating the blowback fuel amount fb. Only one of the inner injection start timing TD and the injection division rate γ may be included. Even in such a case, the blowback fuel amount fb can be estimated with sufficient accuracy.

  Further, the parameters other than the in-cylinder injection start timing TD and the injection ratio γ among the basic parameters for estimating the blowback fuel amount fb are not necessarily all those described in the first embodiment. Also good. For example, in the case of a system that does not include the variable valve mechanism 50 of the intake valve 12, the valve timing VT and the valve lift amount VL do not need to be included in the basic parameters for estimating the blowback fuel amount fb. Conversely, parameters that are not described in the first embodiment may be further included as parameters that serve as a basis for estimating the blowback fuel amount fb.

  In Embodiment 1 described above, the amount of blowback fuel fb is calculated by a method of multiplying a reference amount by a plurality of correction coefficients obtained by referring to a plurality of maps. The calculation method of fb is not limited to such a method. For example, a method using a known cylinder model capable of calculating the flow rate in the intake port 18 may be adopted. In this case, the total blowback amount can be calculated by integrating the flow rate in the intake port 18 calculated by the cylinder model over the period during which the blowback occurs. Based on the total blowback amount, the blowback fuel amount fb can be calculated.

  In the first embodiment described above, the engine speed NE, the load factor KL, the valve timing VT, the valve lift amount VL, the total injection amount fi, the in-cylinder injection start timing TD, and the injection division rate γ are the first and This corresponds to the “predetermined parameter” in the second invention. Further, when the ECU 60 executes the process of step 108, the “blow-back fuel amount estimating means” in the first and second inventions executes the process of step 112, whereby the first and second Each of the “injection amount calculation means” in the present invention is realized.

  Further, in the first embodiment described above, the “means for distributing and adding” in the third aspect of the present invention is realized by the ECU 60 executing the processing of step 112 described above.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 7. The description will focus on the differences from the first embodiment described above, and the description of similar matters will be omitted or simplified. To do. The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 7 described later using the hardware configuration shown in FIG.

[Features of Embodiment 2]
As described above, in the first embodiment, the blow-back correction amount is distributed and included in both the port injection amount fip and the in-cylinder injection amount fid. On the other hand, in the present embodiment, the blow-back correction amount is collectively included only in the in-cylinder injection amount fid. Hereinafter, the calculation method of the port injection amount fip and the in-cylinder injection amount fid in the present embodiment will be specifically described.

[Calculation of port injection amount fip]
In the present embodiment, the in-cylinder fuel intake amount fcp (k), the target air-fuel ratio α (k), the in-cylinder intake air amount m (k), and the injection ratio γ (k) described above. The port injection amount fip is set so that the relationship of the following equation is established.
fcp (k) = γ (k) · m (k) / α (k) (12)
From the above equations (1) and (12), the port injection amount fip can be calculated as the following equation.

[Calculation of in-cylinder injection amount fid]
As described above, the discharged fuel amount fex (k) can be expressed by the following equation by considering the effect of blowback and the effect of the residual gas in the cylinder.
fex (k) = fcp (k) + fcd (k) + fb (k-1) + fr (k-1) -fb (k) -fr (k) (14)
From the equations (4), (9), (12) and (14), the in-cylinder injection amount fid can be calculated as the following equation.

[Blow-back correction fbc]
The second row on the right side of the above equation (15) is obtained by replacing the terms including fb (k) and fb (k-1) on the first row on the right side together as fbc. In the present embodiment, this fbc corresponds to a blowback correction amount for correcting an error due to blowback. That is, the blowback correction amount fbc is expressed by the following equation.
fbc (k) = {fb (k-1) -fb (k)} / {1-Rc (k)} (16)
In the present embodiment, the ECU 60 stores the above expressions (13), (15), and (16).

  In the present embodiment, the following advantages can be obtained by calculating the blowback correction amount fbc only in the in-cylinder injection amount fid. The basis of the blowback correction amount fbc is the blowback fuel amount fb. The actual blowback amount is determined when the intake valve is closed as described above. For this reason, the time when the blow-back fuel amount fb that most closely matches can be calculated is in the vicinity of when the intake valve is closed. On the other hand, since the fuel injected from the port injector 22 cannot be supplied into the cylinder after the intake valve 12 is closed, the port injection timing is set before the intake valve is closed. Therefore, when the blowback correction amount fbc is included in the port injection amount fip, the blowback fuel amount fb must be calculated before the intake valve is closed.

  On the other hand, in the case of in-cylinder injection, fuel can be supplied into the cylinder even after the intake valve 12 is closed, that is, in the compression stroke. Therefore, when the blowback correction amount fbc is included only in the in-cylinder injection amount fid, even if the blowback fuel amount fb is calculated after waiting until the intake valve is closed, the blowback is performed during the compression stroke after the intake valve is closed. It is possible to perform in-cylinder injection in consideration of the correction amount fbc. That is, in the present embodiment, the blowback fuel amount fb can be obtained based on the latest information after waiting until the intake valve is closed, and therefore, the blowback fuel amount fb can be calculated with the best accuracy. For this reason, the deviation of the air-fuel ratio due to the effect of blowback can be corrected with higher accuracy.

  In the present embodiment, for the above reason, the in-cylinder injection start timing TD is set to be during the compression stroke after the intake valve is closed. As described above with reference to FIG. 4, in the range where the in-cylinder injection start timing TD is after the intake valve closing time, the blowback fuel amount fb takes a constant value regardless of the in-cylinder injection start timing TD. . Therefore, in the present embodiment, it is not necessary to add the in-cylinder injection start timing TD to the parameter that is the basis for estimating the blowback fuel amount fb. For this reason, the blowback fuel amount fb is estimated regardless of the in-cylinder injection start timing TD.

  By the way, the blowback correction amount fbc is a balance between the blowback fuel amount fb (k-1) generated in the previous cycle and the blowback fuel amount fb (k) generated in the current cycle, as can be seen from the above equation (16). Is based. For this reason, the blowback correction amount fbc can be a positive value or a negative value. That is, the blowback correction amount fbc has both a case where it is an increase correction and a case where it is a decrease correction.

  During steady operation, generally, the fluctuation per cycle of the blowback correction amount fbc is small. On the other hand, during transient operation, the fluctuation of the blowback correction amount fbc for each cycle tends to increase. If the blow-back correction amount fbc changes significantly with respect to the value in the previous cycle, the fuel injection amount in the current cycle tends to increase or decrease more rapidly than in the previous cycle, so the torque level difference between the current cycle and the previous cycle Is likely to occur. If this torque step becomes too large, a torque shock tends to occur.

  Therefore, in the present embodiment, in order to surely avoid the occurrence of torque shock due to the blowback correction, when the blowback correction amount fbc greatly changes with respect to the value in the previous cycle, the blowback correction amount fbc Only a part was included in the in-cylinder injection amount fid. As a result, it is possible to reliably avoid the occurrence of a torque shock due to the torque step between the current cycle and the previous cycle.

  By the way, in order for the catalyst 42 to exert a good exhaust purification action, the oxygen storage amount of the catalyst 42 (hereinafter referred to as “catalyst oxygen storage amount”) needs to be maintained in an appropriate range. For this reason, in the system of the present embodiment, the air-fuel ratio is adjusted in order to control the catalyst oxygen storage amount within an appropriate range. In such a system, when only a part of the blowback correction amount fbc is included in the in-cylinder injection amount fid in order to prevent the above-described torque shock, the deviation from the target air-fuel ratio α tends to be large. It is difficult to control the oxygen storage amount.

  For example, when the blowback correction amount fbc is a positive value and only a part of the blowback correction amount fbc is included in the in-cylinder injection amount fid, the total fuel injection amount achieves the target air-fuel ratio α. Therefore, the catalyst oxygen storage amount tends to be excessive. Therefore, in the present embodiment, in such a case, when the catalyst oxygen storage amount is actually excessive, it corresponds to the amount not included in the in-cylinder injection amount fid in the blowback correction amount fbc. The amount of fuel to be injected is injected from the in-cylinder injector 24 in the exhaust stroke. Since the fuel injected in this exhaust stroke does not contribute to combustion, the torque is not increased. Therefore, the balance of the catalyst oxygen storage amount can be maintained without generating a torque shock due to a sudden increase in torque.

  On the other hand, when the blowback correction amount fbc is a negative value and only a part of the blowback correction amount fbc is included in the in-cylinder injection amount fid, the total fuel injection amount achieves the target air-fuel ratio α. Since the amount exceeds the amount, the catalyst oxygen storage amount tends to be insufficient. Therefore, in the present embodiment, in such a case, and when the catalyst oxygen storage amount is actually insufficient, the amount that is not included in the in-cylinder injection amount fid in the blowback correction amount fbc is calculated in the next cycle. The port injection amount fip in the next cycle is reduced by being included in the port injection amount fip. That is, by distributing the blowback correction amount fbc between the current cycle and the next cycle, the torque step due to the decrease in the fuel injection amount can be dispersed and reduced. For this reason, the balance of the catalyst oxygen storage amount can be maintained without generating a torque shock.

[Specific Processing in Second Embodiment]
FIG. 7 is a flowchart of a routine executed by the ECU 60 in the present embodiment in order to realize the above function. This routine is executed separately for each cylinder of the internal combustion engine 6. This routine is executed every time the target cylinder operates for one cycle.

  According to the routine shown in FIG. 7, it is first determined whether or not 1 is set in the flag F (step 130). The meaning of this flag F will be described later. The initial value of the flag F is 0. For this reason, when this routine is executed for the first time, it is recognized that F = 1 is not satisfied in step 130. In this case, the port injection amount fip is then calculated (step 132). The calculation of the port injection amount fip is performed as follows.

  The ECU 60 updates the adhesion amounts fwp, fwv, and fwc to the latest values for each cycle in the same manner as the routine shown in FIG. Further, in step 132, the same processing as in steps 102, 106 and 110 in the routine shown in FIG. 6 is performed, and the adhesion rate Rp, Rv, Rc, the residual rate Pp, Pv, Pc, the injection ratio γ, The in-cylinder residual fuel amount fr is calculated. The ECU 60 calculates the port injection amount fip by substituting these parameters into the above equation (13).

  In the routine shown in FIG. 7, next, fuel for the calculated port injection amount fip is injected from the port injector 22 (step 134). The port injection timing is set before the intake valve 12 is opened or during the opening period of the intake valve 12.

Next, a change rate S of the blowback correction amount fbc is calculated (step 136). It is determined whether or not the change rate S is so large that the change in the blowback correction amount fbc (k) of the current cycle with respect to the blowback correction amount fbc (k-1) of the previous cycle is likely to cause a torque shock. It is the basis to do. Specifically, the change rate S is defined as a value obtained by dividing the difference between the blowback correction amount fbc (k) for the current cycle and the blowback correction amount for the previous cycle by the total injection amount fi (k), as shown in the following equation. Is done.
S = {fbc (k) -fbc (k-1)} / fi (k) (17)

  In the calculation process of the change rate S in step 136, first, the blowback fuel amount fb (k) of the current cycle is calculated. The calculation process of the blowback fuel amount fb (k) is performed in the same manner as the step 108 of the routine shown in FIG. 6 described above except that the in-cylinder injection start timing TD is not used as a basis for calculation. Here, the blowback fuel amount fb (k) is near the time when the intake valve is closed, which is the timing when the estimation accuracy becomes the highest, and the engine speed NE, the load factor KL, the valve timing VT, the valve lift VL, the total injection After obtaining the latest values of the quantity fi and the injection ratio γ, the values are calculated based on these values. Thereby, in this embodiment, the blowback fuel amount fb can be calculated with particularly high accuracy.

  In the processing of step 136, the ECU 60 next substitutes the calculated fb (k) of the current cycle and fb (k-1) calculated in the previous processing cycle into the above equation (16). Thus, the blowback correction amount fbc (k) for the current cycle is calculated. Then, the ECU 60 substitutes the calculated blowback correction amount fbc (k) of the current cycle and fbc (k-1) calculated in the previous processing cycle into the above equation (17), thereby changing the rate of change S. Is calculated.

  In the routine shown in FIG. 7, it is next determined whether or not the absolute value of the change rate S of the blowback correction amount fbc is larger than a predetermined determination value (step 138). As a result, when it is recognized that the absolute value of the rate of change S is equal to or less than the determination value, torque shock occurs even if the total amount of the blowback correction amount fbc (k) is included in the in-cylinder injection amount fid. It can be judged that there is no fear. Therefore, in this case, the in-cylinder injection amount fid is then calculated based on the above equation (15) (step 140), and the calculated amount of fuel is actually injected from the in-cylinder injector 24. (Step 142). This in-cylinder injection timing is during the compression stroke after the intake valve is closed.

  On the other hand, if it is found in step 138 that the absolute value of the rate of change S is larger than the determination value, torque shock occurs when the total amount of the blowback correction amount fbc (k) is included in the in-cylinder injection amount fid. It can be determined that In this case, in-cylinder injection amount fid is calculated by including only a part of the blowback correction amount fbc (k) in order to surely avoid the torque shock (step 144). Specifically, in-cylinder injection is performed based on an equation in which fbc (k) in the above equation (15) is changed to β · fbc (k) multiplied by a predetermined coefficient β satisfying 0 <β <1. The quantity fid is calculated. Thereafter, the calculated amount of fuel is actually injected from the in-cylinder injector 24 (step 146). This in-cylinder injection timing is during the compression stroke after the intake valve is closed. According to such processing, the torque step is reduced and the occurrence of torque shock is reliably prevented.

  In the present embodiment, as described above, the blowback fuel amount fb can be calculated with particularly high accuracy, and the accuracy of the blowback correction amount fbc (k) obtained based on this can be extremely high. For this reason, the deviation of the air-fuel ratio due to the blowback effect can be corrected with particularly high accuracy.

  In addition, in the calculation process of the blowback fuel amount fb and the calculation process of the in-cylinder injection amount fid, the adhesion rate Rp, Rv, Rc, the residual rate Pp, Pv, Pc, the injection division rate γ, the in-cylinder residual fuel amount For fr, the value calculated in step 132 may be used, but a value recalculated based on the latest information may be used in order to further improve accuracy.

  When the in-cylinder injection during the compression process is performed with the in-cylinder injection amount fid in which only a part of the blowback correction amount fbc (k) (β · fbc (k)) is included by the processing of step 146 above. Next, it is determined whether the blowback correction amount fbc (k) is positive or negative (step 148).

  If it is determined in step 148 that the blowback correction amount fbc (k) is a positive value, it is next determined whether or not the catalyst oxygen storage amount is excessive (step 150). In another routine, the ECU 60 estimates the catalyst oxygen storage amount by a known method, and performs the determination in step 150 based on the estimated value. As a result, when it is recognized that the catalyst oxygen storage amount is excessive, it corresponds to the remaining amount (1-β) · fbc for the blow-back correction that is not included in the in-cylinder injection amount fid in step 144. An amount of fuel is injected from the in-cylinder injector 24 in accordance with the exhaust stroke (step 152). Thereby, the catalyst oxygen storage amount can be reduced, and the catalyst oxygen storage amount can be brought close to a preferable range.

The in-cylinder injection in the exhaust stroke in step 152 is not limited to after exhaust bottom dead center, and may be started before exhaust bottom dead center after the exhaust valve is opened.
Further, if it is not recognized in step 150 that the catalyst oxygen storage amount is excessive, it is considered that it is not necessary to perform fuel injection in the exhaust stroke, and thus the processing in step 152 is skipped.

  On the other hand, if it is determined in step 148 that the blowback correction amount fbc (k) is a negative value, whether or not the catalyst oxygen storage amount is insufficient is determined next. A determination is made based on the estimated value (step 154). As a result, when it is recognized that the catalyst oxygen storage amount is insufficient, it corresponds to the remaining amount (1-β) · fbc for the blow-back correction that is not included in the in-cylinder injection amount fid in the above step 144. By adding this amount to the port injection amount fip in the next processing cycle, the port injection amount fip in the next cycle of the internal combustion engine 6 is reduced. Therefore, in this case, 1 is set in the flag F to indicate that the remaining portion (1-β) · fbc for the blowback correction in the next processing cycle should be included in the port injection amount fip (step 156). Thereafter, the current processing cycle is terminated.

  If there is no shortage of the catalyst oxygen storage amount in step 154, it is considered unnecessary to decrease the port injection amount fip of the next cycle of the internal combustion engine 6, and therefore the port injection amount in the next processing cycle. In order to indicate that fip should be calculated as usual, 0 is set in the flag F (step 158), and then the current processing cycle is terminated.

  Further, when the blowback correction amount fbc (k) is a positive value, and further, when the entire blowback correction amount fbc (k) is included in the in-cylinder injection amount fid and the in-cylinder injection is performed. In addition, the flag F is set to 0 to indicate that the port injection amount fip should be calculated as usual in the next processing cycle (step 158), and then the current processing cycle is terminated.

  If the flag F is set to 1 in step 156, it is recognized that F = 1 is established in step 130 when the next processing cycle is executed. In this case, the remaining portion (1-β) · fbc for the blow-back correction of the previous cycle is included to calculate the port injection amount fip (step 160). The processing in step 160 is performed in the same manner as in step 132 except that (1-β) · fbc is included.

  According to the processing of step 160 above, when the blowback correction amount fbc is negative, the remaining amount (1-β) · fbc for the blowback correction, which was insufficient in the previous cycle, is calculated from the port injection amount fip in the current cycle. Can be deducted. Thereby, the catalyst oxygen storage amount can be increased, and the catalyst oxygen storage amount can be brought close to a preferable range.

  By the way, in the second embodiment described above, when the blowback correction amount fbc is negative and the remaining (1-β) · fbc for the blowback correction is included in the fuel injection amount of the next cycle, this is port injection. Although only the amount fip is included, it may be included in the in-cylinder injection amount fid.

  In the second embodiment described above, the remaining amount (1-β) · fbc for the blowback correction when the blowback correction amount fbc is negative is included only in the fuel injection amount of the next cycle. These may be further dispersed and included in a plurality of cycles. As a result, the torque step can be further dispersed and reduced.

  In the second embodiment described above, the engine speed NE, the load factor KL, the valve timing VT, the valve lift amount VL, the total injection amount fi, and the injection division rate γ are the “predetermined parameters” in the first invention. It corresponds to. Further, when the ECU 60 executes the process of step 136 described above, the “blow-back fuel amount estimating means” in the first invention executes the processes of steps 132 and 140 described above. Each of the “injection amount calculation means” is realized.

  Further, in the above-described second embodiment, the ECU 60 executes the process of step 140, so that the “means for calculating only the in-cylinder injection amount” in the fourth invention is the process of steps 142 and 146. By executing the above, the “injection timing control means” in the fifth aspect of the invention executes the processing of step 144, and the “partial counting means” in the sixth aspect of the invention executes the processing of step 152. Thus, the “exhaust stroke injection means” in the seventh aspect of the invention realizes the “injection amount reduction means” of the eighth aspect of the invention by executing the processing of step 160.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the fuel behavior model used in Embodiment 1 of this invention. It is a figure for demonstrating the fuel behavior model used in Embodiment 1 of this invention. 6 is a graph showing the relationship between the amount of blowback fuel fb and the in-cylinder injection start timing TD under conditions where other parameters are constant. 6 is a graph showing the relationship between the blowback fuel amount fb and the injection ratio γ under conditions in which other parameters are constant. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

6 Internal combustion engine 10 Combustion chamber 12 Intake valve 14 Exhaust valve 16 Spark plug 18 Intake port 20 Exhaust port 22 Port injector 24 In-cylinder injector 30 Intake passage 33 Air flow meter 36 Throttle valve 40 Exhaust passage 42 Catalyst 44 Air-fuel ratio sensor 46 Crank angle sensor 60 ECU
fip port injection amount
fid In-cylinder injection amount
fwp port weight
fwv Intake valve adhesion
fwc In-cylinder adhesion amount
fcp In-cylinder fuel intake amount
fcd In-cylinder fuel vaporization
Pp port residual rate
Rp port adhesion rate
Pv Intake valve residual rate
Rv Intake valve adhesion rate
Pc In-cylinder residual rate
Rc In-cylinder adhesion rate
fb Blowback fuel amount
fr Residual fuel amount in cylinder
fex Emission fuel amount
fbc Blow-back correction m In-cylinder intake air amount α Target air-fuel ratio γ Injection ratio

Claims (8)

A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
Blow-back fuel amount estimation means for estimating the amount of fuel contained in the blow-back of intake air from the cylinder to the intake port based on a predetermined parameter;
Based on the amount estimated by the blowback fuel amount estimating means, the amount of blowback correction for correcting the error due to blowback is included, and the port injection amount injected from the port injector and the cylinder injection injected from the cylinder injector An injection amount calculating means for calculating an injection amount;
With
The predetermined parameter includes an injection ratio of the port injector and the in-cylinder injector,
The control apparatus for an internal combustion engine, wherein the blowback fuel amount estimation means estimates the blowback fuel amount less when the injection ratio of the in-cylinder injector is large than when the injection ratio is small . A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
Blow-back fuel amount estimation means for estimating the amount of fuel contained in the blow-back of intake air from the cylinder to the intake port based on a predetermined parameter;
Based on the amount estimated by the blowback fuel amount estimating means, the amount of blowback correction for correcting the error due to blowback is included, and the port injection amount injected from the port injector and the cylinder injection injected from the cylinder injector An injection amount calculating means for calculating an injection amount;
With
The predetermined parameter includes an injection start time of the in-cylinder injector,
The control apparatus for an internal combustion engine, characterized in that the blowback fuel amount estimation means estimates that the blowback fuel amount is smaller when the injection start timing of the in-cylinder injector is late than when it is early .   3. The control apparatus for an internal combustion engine according to claim 1, wherein the injection amount calculating means includes means for distributing the blow-back correction amount into both the port injection amount and the in-cylinder injection amount. .   3. The control device for an internal combustion engine according to claim 1, wherein the injection amount calculation means includes means for calculating the blowback correction amount only in the in-cylinder injection amount.   An injection timing control means is further provided for setting the injection start timing of the in-cylinder injector to a timing after the intake valve is closed when the blow-back correction amount is included only in the in-cylinder injection amount. Item 5. The control device for an internal combustion engine according to Item 4.   The injection amount calculation means calculates the blow-back correction amount when the change in the blow-back correction amount of the current cycle relative to the blow-back correction amount of the previous cycle is larger than a determination value when the blow-back correction amount is included in only the in-cylinder injection amount. 6. The control apparatus for an internal combustion engine according to claim 4, further comprising a partial counting means for counting only a part of the amount into the in-cylinder injection amount.   An amount corresponding to the remainder of the blowback correction when the blowback correction is a positive value and only a part of the blowback correction is included in the in-cylinder injection amount by the partial calculation means. The control apparatus for an internal combustion engine according to claim 6, further comprising exhaust stroke injection means for injecting the fuel from the in-cylinder injector in an exhaust stroke.   When the blowback correction amount is a negative value and only a part of the blowback correction amount is included in the in-cylinder injection amount by the partial calculation means, the remaining portion of the blowback correction amount is set to the next cycle or later. 8. The control apparatus for an internal combustion engine according to claim 6, further comprising injection amount reduction means for reducing the injection amount after the next cycle by being included in the injection amount.

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