JP4281672B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine having both a port injector and an in-cylinder injector.

2. Description of the Related Art Conventionally, as described in Patent Document 1 and Patent Document 2, for example, a dual injector system including a port injector that injects fuel into an intake port and an in-cylinder injector that injects fuel into a cylinder is known. Yes.
Japanese Patent Laid-Open No. 11-303669 JP-A-5-2321221

  In the dual injector system as described above, a method of determining the fuel injection amount from each injector in consideration of the amount of fuel adhering to the wall surface of the port or the cylinder wall surface using a fuel behavior model can be considered. However, the fuel behavior model is likely to become unstable or vibrated under operating conditions in which the fuel adhesion rate and the residual rate, which are parameters for calculating the fuel injection amount, are large. For this reason, under such conditions, the accuracy of the model calculation decreases, and there is a possibility that the amount of fuel supplied into the cylinder cannot be optimally controlled.

  The present invention has been made to solve the above-described problems, and in a fuel injection control device for an internal combustion engine having both a port injector and an in-cylinder injector, the fuel injection amount from each injector is determined by model calculation. In this case, an object of the present invention is to optimally control the amount of fuel supplied into the cylinder by suppressing a decrease in the accuracy of the model calculation due to an increase in the adhesion rate and the residual rate of the fuel.

In order to achieve the above object, the present invention provides a fuel injection control device for an internal combustion engine comprising a port injector for injecting fuel into an intake port and an in-cylinder injector for injecting fuel into a cylinder.
A required fuel amount calculating means for calculating an in-cylinder required fuel amount according to an operating state of the internal combustion engine;
An injection ratio setting means for setting an injection ratio between the fuel injection amount from the port injector and the fuel injection amount from the in-cylinder injector;
Based on the in-cylinder required fuel amount and the injection ratio, the fuel injection amount by the port injector and the in-cylinder are calculated by model calculation that takes into account the adhesion of fuel in the vicinity of the intake port and the adhesion of fuel in the cylinder. Fuel injection amount calculating means for calculating the fuel injection amount by the injector;
When the fuel adhesion rate and / or residual rate in the vicinity of the intake port exceeds a predetermined reference value, or when the adhesion rate and / or residual rate is expected to exceed a predetermined reference value, the port Injection ratio correction means for correcting the injection ratio so as to reduce the ratio of the fuel injection amount by the injector and increase the ratio of the fuel injection amount by the in-cylinder injector;
It is characterized by having.

  According to the present invention, under the operating conditions in which the fuel adhesion rate and / or the residual rate in the vicinity of the intake port is large, the ratio of the fuel injection amount by the port injector is set small by correcting the injection ratio, and instead the cylinder The ratio of the fuel injection amount by the inner injector is set large. Since the atmospheric temperature and wall surface temperature in the cylinder are higher than those in the intake port, the adhesion rate and residual rate of the fuel are smaller in the cylinder than in the intake port. For this reason, as described above, the ratio of the fuel injection amount by the port injector is decreased, and the ratio of the fuel injection amount by the in-cylinder injector is increased accordingly, thereby increasing the fuel adhesion rate and the residual rate in the vicinity of the intake port. Even in such a case, the influence on the accuracy of the model calculation can be reduced. As a result, in the model calculation of the fuel injection amount from each injector, a decrease in the accuracy can be suppressed, and the amount of fuel supplied into the cylinder is accurately controlled to the amount of fuel required according to the operating state of the internal combustion engine. It becomes possible to do.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine system to which a fuel injection control device according to Embodiment 1 of the present invention is applied. First, the configuration of an internal combustion engine system to which the present invention is applied will be described with reference to FIG.

  The internal combustion engine according to the present embodiment includes a cylinder block 6 in which a piston 8 is disposed, and a cylinder head 4 assembled to the cylinder block 6. A space from the upper surface of the piston 8 to the cylinder head 4 forms a combustion chamber 10, and an intake port 18 and an exhaust port 20 are formed in the cylinder head 4 so as to communicate with the combustion chamber 10. An intake valve 12 for controlling the communication state between the intake port 18 and the combustion chamber 10 is provided at a connection portion between the intake port 18 and the combustion chamber 10, and an exhaust gas is provided at a connection portion between the exhaust port 20 and the combustion chamber 10. An exhaust valve 14 for controlling the communication state between the port 20 and the combustion chamber 10 is provided. A spark plug 16 is attached to the cylinder head 4 so as to protrude from the top of the combustion chamber 10 into the combustion chamber 10.

  An intake passage 30 for introducing air into the combustion chamber 10 (in the cylinder) is connected to the intake port 18 of the cylinder head 4. 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 56 for detecting the intake amount of air is disposed downstream of the air cleaner 32. 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 sensor 54 for detecting the opening degree.

  The internal combustion engine according to the present embodiment is configured as a dual injector system including two injectors 38 and 70 in each cylinder. One injector 38 is a port injector provided in the vicinity of the intake port 18 of the intake passage 30, and injects fuel into the intake port 18. The other injector 70 is an in-cylinder injector provided to face the inside of the combustion chamber 10 to the cylinder head 4, and directly injects fuel into the combustion chamber 10.

  In addition, an exhaust passage 20 for discharging combustion gas generated by combustion in the combustion chamber 10 as exhaust gas is connected to the exhaust port 20 of the cylinder head 4. A catalyst 42 for purifying exhaust gas is provided in the exhaust passage 40. An air-fuel ratio sensor 58 for detecting the air-fuel ratio of the exhaust gas is disposed upstream of the catalyst 42 in the exhaust passage 40.

  The internal combustion engine according to the present embodiment includes an ECU (Electronic Control Unit) 50 as its control device. Various devices such as the port injector 38, the in-cylinder injector 70, the throttle valve 36, and the spark plug 16 are connected to the output side of the ECU 50. On the input side of the ECU 50, in addition to the air flow meter 56, the throttle sensor 54, and the air-fuel ratio sensor 58 described above, there are various types such as a crank angle sensor 52 that detects the rotation angle of the crankshaft 24 and a water temperature sensor 60 that detects the cooling water temperature. Sensors are connected. The ECU 50 drives each device according to a predetermined control program based on the output of each sensor.

  Next, the concept of fuel injection control in the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram for explaining the concept of fuel injection control in the present embodiment, and is a diagram schematically showing the behavior of fuel in the internal combustion engine.

  In FIG. 2, the symbol “fip” represents the amount of fuel injected from the port injector 38 (hereinafter referred to as port injection amount fi). The fuel injected from the port injector 38 is not all sucked into the combustion chamber 10, but a part of the fuel adheres to the wall surface of the intake port 18 and the intake valve 12. The symbol “fwp” represents the amount of fuel that adheres to the wall surface of the intake port 18 and is not sucked into the combustion chamber 10 (hereinafter referred to as “port adhesion amount fwp”). The symbol “fwv” adheres to the intake valve 12 and 10 represents the amount of fuel that is not sucked into the valve 10 (hereinafter referred to as valve attachment amount fwv). The fuel adhering to the wall surface or the like is vaporized and is sucked into the combustion chamber 10. Therefore, the portion of the fuel injected from the port injector 38 that has not adhered to the wall surface and the portion that has vaporized the fuel that has adhered to the wall surface are sucked into the combustion chamber 10 from the intake port 18. Become.

  In FIG. 2, the symbol “fid” represents the amount of fuel injected from the in-cylinder injector 70 (hereinafter referred to as fuel injection amount fid). Not all of the fuel injected from the in-cylinder injector 70 exists in the atomized state in the combustion chamber 10, but a part of the fuel adheres to the wall surface of the combustion chamber 10. The symbol “fwc” represents the amount of fuel adhering to the wall surface of the combustion chamber 10 (hereinafter referred to as in-cylinder adhesion amount fwc). Since the fuel adhering to the wall surface of the combustion chamber 10 is vaporized, the fuel injected from the in-cylinder injector 70 does not adhere to the wall surface of the combustion chamber 10 and to the wall surface. There will be some fuel vaporized.

  In FIG. 2, the symbol “fc” represents the amount of fuel supplied into the combustion chamber 10 (hereinafter referred to as in-cylinder fuel amount fc). The fuel is mixed with new gas sucked into the combustion chamber 10 from the intake port 18 and exists in the state of an air-fuel mixture. The symbol “Ga” represents the amount of new gas flowing into the combustion chamber 10 (hereinafter referred to as intake air amount Ga). The intake air amount Ga can be detected by an air flow meter 56 (see FIG. 1).

The in-cylinder fuel amount fc is a fuel amount (in-cylinder required fuel amount) required to be present in the combustion chamber 10 in accordance with the operating state of the internal combustion engine. As a method of calculating the in-cylinder fuel amount fc, a method of calculating by dividing the measured value of the intake air amount Ga by the target air-fuel ratio AFR is generally used. This is based on the premise that the air-fuel ratio AFRe of the exhaust gas matches the air-fuel ratio AFRc of the new gas calculated by the following equation (1).
AFRc = Ga / fc (1)

  However, in the combustion chamber 10, not only new gas sucked in the intake stroke of the current cycle but also residual gas that has not been discharged in the exhaust stroke of the previous cycle exists. During transient operation, the air-fuel ratio of the residual gas does not necessarily match the air-fuel ratio AFRc of the new gas, so depending on the general method described above, the air-fuel ratio AFRe of the exhaust gas may not necessarily match the target air-fuel ratio AFR. Can not. Therefore, in the system of the present embodiment, the air-fuel ratio AFRe of the exhaust gas becomes the target air-fuel ratio AFR in consideration of the influence of the residual gas in the cylinder and, more strictly, in consideration of the amount of fuel remaining in the cylinder. As described above, the fuel injection amounts fip and fid from the injectors 38 and 70 are calculated in principle.

  In FIG. 2, the symbol “Gr” represents the amount of gas remaining in the combustion chamber 10 at the start of intake (hereinafter referred to as in-cylinder residual gas amount Gr). The symbol “fr” represents the amount of fuel (burned fuel) contained in the residual gas (hereinafter referred to as in-cylinder residual fuel amount fr). Both the in-cylinder residual gas amount Gr and the in-cylinder residual fuel amount fr have a correlation with the operating state of the internal combustion engine. For this reason, the values of the in-cylinder residual gas amount Gr and the in-cylinder residual fuel amount fr are estimated on the vehicle by grasping the relationship between them and the operating state of the internal combustion engine in advance and creating a map. be able to.

In FIG. 2, the symbol “Gex” represents the amount of exhaust gas discharged from the combustion chamber 10 during one cycle operation (hereinafter referred to as exhaust gas amount Gex). The exhaust gas amount Gex can be expressed by using the intake air amount Ga and the cylinder residual gas amount Gr described above. At the start of the current cycle (referred to as k cycle), there is an in-cylinder residual gas in an amount represented by Gr (k-1) remaining in the cylinder during the exhaust stroke of the previous cycle. If the air amount represented by Ga (k) is inhaled during the intake stroke of the current cycle, the total in-cylinder gas amount at the end of the intake stroke of the current cycle is represented by Ga (k) + Gr (k-1). The amount will be. In the exhaust stroke of the internal combustion engine, a part of the in-cylinder total gas amount Ga (k) + Gr (k-1) is discharged as an exhaust gas amount, and the remaining part remains in the cylinder at the start of the next cycle. The residual gas amount Gr (k). Therefore, the exhaust gas amount Gex (k) in the current cycle can be expressed as the following equation (2).
Gex (k) = Ga (k) + Gr (k-1) -Gr (k) ... (2)

Further, the symbol “fex” represents the amount of fuel (burned fuel) included in the exhaust gas and discharged (hereinafter referred to as the discharged fuel amount fex). The discharged fuel amount fex can be expressed by using the in-cylinder fuel amount fc and the in-cylinder residual fuel amount fr described above. It is assumed that the in-cylinder residual fuel amount at the start of the current cycle is fr (k), and that the in-cylinder residual fuel amount at the end of the current cycle, that is, the in-cylinder residual fuel amount in the next cycle is fr (k). For example, the relationship between the in-cylinder fuel amount fc (k) in the current cycle and the discharged fuel amount fex (k) in the current cycle can be expressed as the following equation (3).
fex (k) = fc (k) + fr (k-1) -fr (k) ... (3)

The air-fuel ratio AFRe of the exhaust gas detected by the air-fuel ratio sensor 58 can be expressed as follows using the exhaust gas amount Gex and the exhaust fuel amount fex.
AFRe = Gex / fex ... (4)
Therefore, from the above equations (2) to (4), the condition for making the air-fuel ratio AFRe (k) of the exhaust gas in the current cycle coincide with the target air-fuel ratio AFR (k) is expressed by the following equation (5): be able to.
AFR (k) = Gex (k) / fex (k)
= {Ga (k) + Gr (k-1) -Gr (k)} / {fc (k) + fr (k-1) -fr (k)} ... (5)

That is, the condition for setting the air-fuel ratio AFRe (k) of the exhaust gas in the current cycle to the target air-fuel ratio AFR (k) is that the fuel amount fc (k) flowing into the cylinder during the current cycle is expressed by the following equation (6) It will be a value represented by.
fc (k) = {Ga (k) + Gr (k-1) -Gr (k)} / AFR (k) -fr (k-1) + fr (k) ... (6)
In other words, if the in-cylinder fuel amount fc (k) in the current cycle is calculated according to the above equation (6), the air-fuel ratio AFRe (k) of the exhaust gas in the current cycle is made to coincide with the target air-fuel ratio AFR (k). It becomes possible.

  Next, an example of a method for calculating the fuel injection amounts fip and fid from the injectors 38 and 70 based on the in-cylinder fuel amount fc will be described. FIG. 3 is a view for explaining a fuel behavior model representing the relationship between the fuel injection amounts fip, fid from the injectors 38, 70 and the in-cylinder fuel amount fc. Based on this model, the system of the present embodiment calculates each fuel injection amount fip, fid corresponding to the in-cylinder fuel amount fc.

  Part of the fuel injected from the port injector 38 adheres to the wall surface of the intake port 18 and the intake valve 12, and the remaining part flows into the combustion chamber 10. Assuming that the rate at which the injected fuel adheres to the wall surface of the intake port 18 is “attachment rate Rp” and the rate at which the injected fuel adheres to the intake valve 12 is “attachment rate Rv”, of the newly injected fuel, the intake port 18 The amount of fuel adhering to the wall surface is represented by “Rp × fip”, and the amount of fuel adhering to the intake valve 12 is represented by “Rv × fip”. On the other hand, of the injected fuel, the amount of fuel sucked into the combustion chamber 10 is represented by “(1−Rp−Rv) × fip”.

  In addition to the fuel “(1-Rp-Rv) × fip” supplied directly from the port injector 38, vaporized fuel generated by vaporization of the fuel attached to the port and the fuel attached to the valve flows into the combustion chamber 10. . Assuming that the ratio of the fuel adhering to the port 18 remaining on the wall surface of the intake port 18 is the “residual rate Pp”, the port adhering amount fwp generated in the previous cycle is represented by “Pp × fwp”. The amount of fuel remaining in the port remains as it is, while the amount of fuel represented by “(1-Pp) × fwp” is sucked into the combustion chamber 10. Further, if the ratio of the fuel adhering to the valve while remaining on the intake valve 12 is “residual rate Pv”, the valve adhering amount fwv generated in the previous cycle is represented by “Pv × fwv”. The amount of fuel remains in the valve-attached fuel, while the amount of fuel represented by “(1-Pv) × fwv” is sucked into the combustion chamber 10.

Therefore, the port adhesion amount at the start of the k-th cycle (for example, at the start of the intake stroke) is fwp (k) and the valve adhesion amount is fwv (k), and the port adhesion rate and valve adhesion rate in the k-th cycle are Rp (k), Rv (k), port residual ratio, valve residual ratio are Pp (k) and Pv (k), respectively, and when the fuel injection amount in the kth cycle is fip (k), kth The port adhesion amount fwp (k + 1) and the valve adhesion amount fwv (k + 1) in the +1 cycle can be expressed as the following equations (7) and (8), respectively. Further, the amount of fuel fcp (k) from the port injector 38 that flows into the combustion chamber 10 from the intake port 18 in the k-th cycle can be expressed as the following equation (9).
fwp (k + 1) = Pp (k) × fwp (k) + Rp (k) × fip (k) (7)
fwv (k + 1) = Pv (k) × fwv (k) + Rv (k) × fip (k) (8)
fcp (k) = (1-Rp (k) -Rv (k)) × fip (k) + (1-Pp (k)) × fwp (k) + (1-Pv (k)) × fwv (k ) ... (9)

  On the other hand, part of the fuel injected from the in-cylinder injector 70 adheres to the wall surface of the combustion chamber 10, and the remaining part exists in the combustion chamber 10 in a vaporized (or atomized) state. Assuming that the ratio of the injected fuel adhering to the wall surface of the combustion chamber 10 is “adhesion rate Rc”, the amount of the fuel adhering to the wall surface of the combustion chamber 10 among the newly injected fuel is “Rc × fid”. Will be represented. On the other hand, of the injected fuel, the amount of fuel present in the combustion chamber 10 in a vaporized (or atomized) state is represented by “(1-Rc) × fid”.

  In the combustion chamber 10, in addition to the fuel “(1-Rc) × fid” supplied directly from the in-cylinder injector 70, there is vaporized fuel generated by the vaporization of the in-cylinder attached fuel. If the remaining ratio of the in-cylinder attached fuel remaining on the wall surface of the combustion chamber 10 is “residual rate Pc”, the in-cylinder attached amount fwc generated in the previous cycle is expressed by “Pc × fwc”. The amount of fuel that remains in the cylinder remains as it is, and the amount of fuel represented by “(1-Pc) × fwc” is vaporized in the combustion chamber 10.

Therefore, the in-cylinder adhesion amount at the start of the k-th cycle is fwc (k), the in-cylinder adhesion rate and the in-cylinder residual rate in the k-th cycle are Rc (k) and Pc (k), respectively. When the fuel injection amount in the cycle is fid (k), the in-cylinder attachment amount fwc (k + 1) in the (k + 1) th cycle can be expressed as the following equation (10). Further, the fuel amount fcd (k) from the in-cylinder injector 70 existing in the vaporized (or atomized) state in the combustion chamber 10 in the k-th cycle can be expressed as the following equation (11).
fwc (k + 1) = Pc (k) × fwc (k) + Rc (k) × fid (k) (10)
fcd (k) = (1-Rc (k)) × fid (k) + (1-Pc (k)) × fwc (k) (11)

From the above equations (9) and (11), the total amount of fuel (in-cylinder fuel amount) fc (k) supplied into the combustion chamber 10 in the k-th cycle is expressed as the following equation (12). Can do.
fc (k) = fcp (k) + fcd (k)
= (1-Rp (k) -Rv (k)) × fip (k) + (1-Pp (k)) × fwp (k) + (1-Pv (k)) × fwv (k)
+ (1-Rc (k)) × fid (k) + (1-Pc (k)) × fwc (k) (12)

As shown in the above equation (12), the in-cylinder fuel amount fc (k) is expressed as a function of the port injection amount fip (k) and the in-cylinder injection amount fid (k). In the fuel injection control in the present embodiment, the port injection amount fip (k) and the in-cylinder injection amount fid (k) satisfying the above equation (12) are uniquely determined. The injection ratio γ (k) between the port injection amount fip (k) and the in-cylinder injection amount fid (k) is set. The ECU 50 stores in advance a map that defines the relationship between the injection ratio and the operating state of the internal combustion engine. From this map, the injection ratio γ (k) corresponding to the operating state of the internal combustion engine is read for each cycle.
fip (k) × (1-γ (k)) = fid (k) × γ (k) (13)

According to the above equations (6), (12), and (13), the port injection amount fip (k) and the in-cylinder injection amount necessary for supplying the fuel of fc (k) into the combustion chamber 10. fid (k) can be expressed as the following equations (14) and (15), respectively.
fip (k) = γ (k) / {(1-Rc (k)) × (1-γ (k)) + (1-Rp (k) -Rv (k)) × γ (k)}
× [{Ga (k) + Gr (k-1) -Gr (k)} / AFR (k)-(1-Pp (k)) × fwp (k)
-(1-Pv (k)) × fwv (k)-(1-Pc (k)) × fwc (k) -fr (k-1) + fr (k)] ... (14)
fid (k) = (1-γ (k)) / {(1-Rc (k)) × (1-γ (k)) + (1-Rp (k) -Rv (k)) × γ (k )}
× [{Ga (k) + Gr (k-1) -Gr (k)} / AFR (k)-(1-Pp (k)) × fwp (k)
-(1-Pv (k)) × fwv (k)-(1-Pc (k)) × fwc (k) -fr (k-1) + fr (k)] ... (15)

  The fuel adhesion rates Rp, Rv, Rc and the residual rates Pp, Pv, Pc have a correlation with the operating state of the internal combustion engine. Therefore, if the relationship between them and the operation state of the internal combustion engine is grasped in advance and a map is created, the adhesion rates Rp, Rv, Rc and the residual rates Pp, Pv, Pc are all estimated on the vehicle. Is possible. If they are estimated, the port injection amount fip and the in-cylinder injection amount fid for generating the in-cylinder fuel amount fc can be calculated according to the above equations (14) and (15).

  By the way, the fuel behavior model described above is likely to become unstable or vibrate under operating conditions in which the fuel adhesion rates Rp, Rv, Rc and the residual rates Pp, Pv, Pc, which are parameters, are large. For this reason, under such conditions, the accuracy of the fuel injection amounts fip and fid calculated according to the above equations (14) and (15) will be reduced and supplied to the combustion chamber 10. There is a possibility that the fuel amount cannot be controlled to the in-cylinder fuel amount fc necessary for setting the air-fuel ratio AFRe of the exhaust gas to the target air-fuel ratio AFR.

  Therefore, in the system of the present embodiment, in order to suppress the decrease in the accuracy of the model calculation due to the increase in the fuel adhesion rate and the residual rate, when calculating the port injection amount fip and the in-cylinder injection amount fid by the model calculation, The routine shown in FIG. 4 is executed. FIG. 4 is a flowchart showing the content of the fuel injection amount control executed by the ECU 50 in the present embodiment. The routine shown in FIG. 4 is executed for each cylinder of the internal combustion engine. The routine for each cylinder is started each time the internal combustion engine operates for one cycle, more specifically, every time a predetermined crank angle is realized before fuel injection is started in the target cylinder. Shall.

  In the routine shown in FIG. 4, first, referring to a map stored in advance, each residual rate Pp, Pv, Pc and each adhesion rate Rp, Rv, Rc of the fuel according to the current operating state of the internal combustion engine are calculated. (Step 100). Further, the injection ratio γ between the port injection amount and the in-cylinder injection amount corresponding to the current operating state of the internal combustion engine is calculated with reference to a map stored in advance (step 102).

  In step 104, using the residual ratios Pp, Pv, Pc calculated in step 100, the adhesion rates Rp, Rv, Rc, and the injection ratio γ calculated in step 102, the above equations (14) and ( According to 15), the port injection amount fip and the in-cylinder injection amount fid are calculated. Note that the in-cylinder residual gas amount Gr and the in-cylinder residual fuel amount fr necessary for the calculation of the above formulas (14) and (15) have values corresponding to the current operating state of the internal combustion engine from a previously stored map. Is read. Further, the value detected by the air flow meter 56 is read as the intake air amount Ga.

In step 106, the correction amount fmwpr included in the port injection amount fip calculated in step 104 is calculated by the following equation (16).
fmwpr = | fip- {Ga (k) + Gr (k-1) -Gr (k)} / AFR (k) × γ | ... (16)
{Ga (k) + Gr (k-1) -Gr (k)} / AFR (k) × γ on the right side in the above equation (16) is the case where there is no fuel adhesion, that is, the residual rate Pp, Port injection amount when Pv, Pc and adhesion rate Rp, Rv, Rc are zero. Therefore, the correction amount fmwpr indicates an increase amount or a decrease amount of the port injection amount caused by the fuel adhesion.

  In the next step 108, the correction amount fmwpr calculated in step 106 is compared with a predetermined reference value α. The correction amount fmwpr varies depending on the fuel adhesion rates Rp, Rv, Rc and the residual rates Pp, Pv, Pc, and serves as an index indicating the instability of the fuel behavior model. Therefore, it is considered that the accuracy of the port injection amount fip and the in-cylinder injection amount fid calculated according to the above equations (14) and (15) is lower as the correction amount fmwpr calculated in step 106 is larger. The reference value α is a limit value of a correction amount that can keep the accuracy of the port injection amount fip and the in-cylinder injection amount fid within a predetermined allowable range. If the result of determination in step 108 is that the correction amount fmwpr exceeds the reference value α, processing in step 110 is executed.

  In step 110, the injection ratio γ is corrected so as to decrease the ratio of the port injection amount fip and conversely increase the ratio of the in-cylinder injection amount fid. Specifically, the predetermined correction amount Δγ is subtracted from the current injection ratio γ. After correcting the injection ratio γ, the process of step 104 is executed again, and the port injection amount fip and the in-cylinder injection amount fid are recalculated based on the corrected injection ratio γ. In step 106, the correction amount fmwpr is calculated based on the recalculated port injection amount fip. In step 108, the correction amount fmwpr is compared with the reference value α again. As a result of the comparison, when the correction amount fmwpr is within the reference value α, the port injection amount fip and the in-cylinder injection amount fid are determined to the current calculated values. On the other hand, if the correction amount fmwpr still exceeds the reference value α, the injection ratio γ is corrected again in step 112, and the port injection amount fip and the in-cylinder injection amount fid are recalculated in step 104. Until the correction amount fmwpr calculated in step 106 falls within the reference value α, a series of processes of steps 110, 104, and 106 are repeatedly executed.

  According to the above routine, under the operating conditions in which the fuel adhesion rate and the residual rate are large, the ratio of the port injection amount fip is set small by correcting the injection ratio γ, and instead the ratio of the in-cylinder injection amount fid is large. Is set. Since the atmospheric temperature and wall surface temperature in the combustion chamber 10 are extremely higher than those of the intake port 18, the fuel adhesion rate Pc and the residual rate Rc in the combustion chamber 10 are the fuel adhesion rate Pp, Very small compared to Pv and residual rate Rp, Rv. For this reason, as in this routine, the ratio of the port injection amount fip is decreased, and the ratio of the in-cylinder injection amount fid is increased accordingly, thereby reducing the influence of the fuel adhesion rate and residual rate on the accuracy of the model calculation. be able to. As a result, it is possible to suppress a decrease in accuracy in the model calculation of the fuel injection amounts fip and fid from the respective injectors 38 and 70, and the amount of fuel actually supplied into the combustion chamber 10 depends on the operating state of the internal combustion engine. Therefore, it is possible to accurately control the in-cylinder fuel amount fc required.

  In the above embodiment, the ECU 50 executes the process of step 102 in the fuel injection amount control routine of FIG. 4 so that the “injection ratio setting means” of the present invention executes the process of step 104. The “fuel injection amount calculating means” of the present invention implements the “injection ratio correcting means” of the present invention by executing the processing of Step 106, Step 108 and Step 110. Further, the “required fuel amount calculation means” of the present invention is realized in the process in which the fuel injection amounts fip and fid are calculated in the process of step 104.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The fuel injection control apparatus for an internal combustion engine of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 5 instead of the routine of FIG. 4 in the first embodiment.

  In the first embodiment, the injection ratio γ is corrected based on a comparison between the correction amount fmwpr included in the port injection amount fip and the reference value α, but whether or not the fuel behavior model is unstable depends on the correction amount fmwpr. It depends on the residual ratios Pp, Pv, Pc of the fuel and the adhesion ratios Rp, Rv, Rc. For this reason, instead of making a determination based on the correction amount fmwpr, the correction of the injection ratio γ may be determined based on the fuel residual ratios Pp, Pv, Pc and the adhesion ratios Rp, Rv, Rc. FIG. 5 is a flowchart showing the contents of the fuel injection amount control executed by the ECU 50 in the present embodiment. The routine shown in FIG. 5 is executed for each cylinder of the internal combustion engine. The routine for each cylinder is started each time the internal combustion engine operates for one cycle, more specifically, every time a predetermined crank angle is realized before fuel injection is started in the target cylinder. Shall.

  In the routine shown in FIG. 5, first, referring to a map stored in advance, each residual rate Pp, Pv, Pc of fuel and each adhesion rate Rp, Rv, Rc according to the current operating state of the internal combustion engine are calculated. (Step 200). Further, the injection ratio γ between the port injection amount and the in-cylinder injection amount corresponding to the current operating state of the internal combustion engine is calculated with reference to a map stored in advance (step 202).

  In the next step 204, the port residual ratio Pp calculated in step 202 is compared with a predetermined reference value β1, and the port adhesion ratio Rp is compared with a predetermined reference value β2. The fuel behavior model becomes more unstable as the port residual ratio Pp and the port adhesion ratio Rp are larger. As a result of the determination in step 204, if the port residual ratio Pp exceeds the reference value β1 and the port adhesion ratio Rp exceeds the reference value β2, the process of step 206 is executed.

  In step 206, the injection ratio γ is corrected so as to decrease the ratio of the port injection amount fip and conversely increase the ratio of the in-cylinder injection amount fid. Specifically, the predetermined correction amount Δγ is subtracted from the current injection ratio γ. As a result of the determination in step 204, when the port residual rate Pp is within the reference value β1, or when the port adhesion rate Rp is within the reference value β2, the value of the injection ratio γ is maintained at the value calculated in step 202. Is done.

  In the next step 208, the residual ratios Pp, Pv, Pc calculated in step 200 and the adhesion ratios Rp, Rv, Rc, and the injection ratio γ calculated in step 202 or the injection ratio γ corrected in step 206 are used. The fuel injection amounts fip and fid from the injectors 38 and 70 are calculated using the above equations (14) and (15).

  According to the above routine, as in the first embodiment, even in operating conditions where the fuel adhesion ratios Rp, Rv, Rc and the residual ratios Pp, Pv, Pc are large, they give the accuracy of the model calculation. The influence can be reduced, and a decrease in accuracy can be suppressed in the model calculation of the fuel injection amounts fip and fid from the injectors 38 and 70.

  In the above embodiment, the ECU 50 executes the process of step 202 in the fuel injection amount control routine of FIG. 5 so that the “injection ratio setting means” of the present invention executes the process of step 208. The “fuel injection amount calculating means” of the present invention implements the “injection ratio correcting means” of the present invention by executing the processing of step 204 and step 206. Further, the “required fuel amount calculating means” of the present invention is realized in the process in which the fuel injection amounts fip and fid are calculated in the process of step 204.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the in-cylinder fuel amount (in-cylinder required fuel amount) fc is set so that the air-fuel ratio AFRe of the exhaust gas becomes the target air-fuel ratio AFR, but from the start of the internal combustion engine or fuel cut In a situation where the combustion state in the combustion chamber 10 should be accurately controlled, such as immediately after the return of, the in-cylinder fuel amount fc may be set so that the air-fuel ratio AFRc of the new gas becomes the target air-fuel ratio AFR.

  In the first embodiment, the reference value α for determining the correction of the injection ratio γ is a fixed value. However, a map is created by grasping in advance the relationship with the operating state of the internal combustion engine, The reference value α may be changed according to the operating state of the internal combustion engine. Alternatively, the reference value α may be calculated using a model.

  In the second embodiment, the correction amount Δγ of the injection ratio γ when the port residual rate Pp exceeds the reference value β1 and the port adhesion rate Rp exceeds the reference value β2 is a fixed value, but the port residual rate Pp And the reference value β1 or the difference between the port adhesion rate Rp and the reference value β2. Specifically, the correction amount Δγ may be increased so as to decrease the ratio of the port injection amount fip as the port residual rate Pp and the port adhesion rate Rp increase.

  In the second embodiment, the AND condition is that the port residual ratio Pp exceeds the reference value β1 and the port adhesion ratio Rp exceeds the reference value β2, but the OR condition may be used. Alternatively, the determination may be made based on only one of the port residual rate Pp and the port adhesion rate Rp. Further, instead of the port residual rate Pp and the port adhesion rate Rp, the determination may be made based on the valve residual rate Pv and the valve adhesion rate Rv.

  In the first embodiment, it is predicted whether or not the fuel adhesion rate and the residual rate in the vicinity of the intake port 18 exceed a predetermined reference value based on the correction amount fmwpr included in the port injection amount fip. Further, it may be predicted from the operating state of the internal combustion engine whether or not the adhesion rate and the residual rate exceed a predetermined reference value. In that case, for example, a map defining the relationship between the correction amount Δγ of the injection ratio γ and the operating state of the internal combustion engine is created in advance, and the injection ratio γ is set according to the operating state of the internal combustion engine detected by a sensor or the like. You may make it correct | amend.

1 is a diagram showing a schematic configuration of an internal combustion engine system to which a fuel injection control device as Embodiment 1 of the present invention is applied. FIG. It is a figure for demonstrating the concept of the fuel-injection control in Embodiment 1 of this invention. It is a figure for demonstrating the fuel behavior model showing the relationship between the fuel injection quantity fi and the cylinder fuel amount fc. It is a flowchart of the fuel injection amount control routine performed in Embodiment 1 of the present invention. It is a flowchart of the fuel injection amount control routine performed in Embodiment 2 of the present invention.

Explanation of symbols

10 Combustion chamber 12 Intake valve 14 Exhaust valve 16 Spark plug 18 Intake port 20 Exhaust port 24 Crankshaft 30 Intake passage 36 Throttle valve 38 Port injector 40 Exhaust passage 42 Three-way catalyst 50 ECU
52 Crank angle sensor 56 Air flow meter 58 Air-fuel ratio sensor 70 In-cylinder injector
AFR target air-fuel ratio
AFRc Air-fuel ratio of new gas
AFRe exhaust gas air-fuel ratio
Ga intake air volume
fip port injection amount
Amount of fuel attached to fwp port
Amount of fuel attached to fwv valve
fic In-cylinder injection amount
fwc In-cylinder fuel adhering amount
fc In-cylinder fuel amount
Gr In-cylinder residual gas volume
fr Residual fuel amount in cylinder
Pp port residual rate
Rp port adhesion rate
Pv valve residual rate
Rv Valve adhesion rate
Pc In-cylinder residual rate
Rc In-cylinder adhesion rate
Gex emissions
fex Emission fuel amount

Claims (1)

In a fuel injection control device for an internal combustion engine comprising a port injector for injecting fuel into an intake port and an in-cylinder injector for injecting fuel into a cylinder,
A required fuel amount calculating means for calculating an in-cylinder required fuel amount according to an operating state of the internal combustion engine;
An injection ratio setting means for setting an injection ratio between the fuel injection amount from the port injector and the fuel injection amount from the in-cylinder injector;
Based on the in-cylinder required fuel amount and the injection ratio, the fuel injection amount by the port injector and the in-cylinder are calculated by model calculation that takes into account the adhesion of fuel in the vicinity of the intake port and the adhesion of fuel in the cylinder. Fuel injection amount calculating means for calculating the fuel injection amount by the injector;
When the fuel adhesion rate and / or residual rate in the vicinity of the intake port exceeds a predetermined reference value, or when the adhesion rate and / or residual rate is expected to exceed a predetermined reference value, the port Injection ratio correction means for correcting the injection ratio so as to reduce the ratio of the fuel injection amount by the injector and increase the ratio of the fuel injection amount by the in-cylinder injector;
A fuel injection control device for an internal combustion engine, comprising:

Images