JP2009228447A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine with a port injection valve and a cylinder injection valve, which suppresses a deterioration of mixing of a fuel injected in a cylinder and fresh air, and lowering in an output by suppressing the amount of the fuel to be injected in the cylinder on and after the end period of valve opening period of an inlet valve. <P>SOLUTION: In this device, when the end period CAec of the valve opening period of the cylinder injection valve corresponding to a basic cylinder injection amount "(1-R)×Fbase" based on a basic injection ratio R is determined on the lag side relative to the end period IVC of the valve opening period of the inlet valve, the cylinder injection amount Fic is decided to be one obtained by subtracting a fuel amount ΔFi corresponding to the interval between the end periods CAec and IVC from the basic cylinder injection amount. The end period CAec of the valve opening period of the cylinder injection valve is set at the same period as the end period IVC. The port injection amount Fip is decided to be one obtained by adding the fuel amount ΔFi to a basic port injection amount "R×Fbase". Thus, the fuel amount injected in the cylinder on and after the end period IVC can be zero without changing the total fuel injection amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

Conventionally, a fuel injection valve (hereinafter referred to as a “port injection valve”) that injects fuel in an intake passage upstream of an intake valve of an internal combustion engine (hereinafter also simply referred to as “engine”). ) And a fuel injection valve (hereinafter referred to as “in-cylinder injection valve”) that directly injects fuel in the combustion chamber (hereinafter also referred to as “in-cylinder”). Is widely known (see, for example, Patent Document 1 below). Hereinafter, a system including two fuel injection valves, that is, a port injection valve and an in-cylinder injection valve for each cylinder, is referred to as a “dual injection system”.
JP 2006-283754 A

  In this dual injection system, the fuel directly injected in the cylinder evaporates, whereby the gas in the cylinder and the members (cylinder, piston, etc.) constituting the combustion chamber can be cooled. Therefore, particularly during high-load operation, fuel injection from the in-cylinder injection valve (hereinafter sometimes simply referred to as “in-cylinder injection”) is often performed in order to suppress knocking or the like.

  By the way, in-cylinder injection is often started at a time after the end of the valve opening period of the exhaust valve. In particular, when in-cylinder injection is performed during a high load / high rotation operation, the in-cylinder injection period (that is, the in-cylinder injection valve opening period) becomes longer and the intake valve opening period The end is coming early. As described above, in particular, during high load / high rotation operation, in-cylinder injection may continue from the start timing of in-cylinder injection to a timing that is retarded from the end of the intake valve opening period. Many. In other words, the end of the opening period of the in-cylinder injection valve is more likely to be shifted to the retard side than the end of the opening period of the intake valve.

  When in-cylinder injection is continued in this way, the following problem occurs. When in-cylinder injection is performed during the valve opening period of the intake valve, the fuel from the in-cylinder injection can be mixed well with fresh air due to the continued flow of gas into the cylinder. On the other hand, when the in-cylinder injection is performed after the end of the valve opening period of the intake valve, the inflow of the gas hardly occurs, so that the fuel by the in-cylinder injection is hardly mixed with fresh air. If the degree of mixing of fuel and fresh air is small, a situation may occur in which the output of the engine decreases due to the occurrence of incomplete combustion or the like.

  Here, the amount of fuel that is hard to be mixed after the end of the intake valve opening period is less than the end of the intake valve opening period at the end of the in-cylinder injection period. The larger the degree on the retarded side, the larger. Therefore, even if the total amount of fuel injection per cycle is the same, the engine output decreases as the end of the in-cylinder injection period is more retarded than the end of the intake valve opening period. The degree can be greater.

  Therefore, an object of the present invention is to reduce the amount of fuel that is difficult to be mixed among the fuels produced by in-cylinder injection and reduce the degree of engine output in a fuel injection control device for an internal combustion engine having a dual injection system. It is to provide what can be suppressed.

  A fuel injection control device according to the present invention is applied to an internal combustion engine equipped with a dual injection system, and includes a port injection amount that is an amount of fuel injected by the port injection valve, an opening period of the port injection valve, And a port injection determination means for determining a basic port injection amount, a basic port injection start time, and a basic port injection end time based on the operating state of the internal combustion engine, and an amount of fuel injected by the in-cylinder injection valve The basic in-cylinder injection amount, the basic in-cylinder injection start time, and the basic in-cylinder injection are determined based on the operating state of the internal combustion engine. In-cylinder injection determining means for determining at the end.

  Here, the basic port injection amount and the basic in-cylinder injection amount are, for example, the air-fuel ratio targeted by the air-fuel ratio of the air-fuel mixture supplied to the engine (hereinafter sometimes simply referred to as “air-fuel ratio”). May be determined so as to coincide with a target air-fuel ratio (for example, the theoretical air-fuel ratio). Further, the basic port injection start period and the basic in-cylinder injection start period may be determined, for example, at the second half of the exhaust stroke and the first half of the intake stroke. In addition, the basic port injection end is determined based on, for example, the basic port injection amount and the basic port injection start, and the basic in-cylinder injection end is based on, for example, the basic in-cylinder injection amount and the basic in-cylinder injection start. May be determined.

  The fuel injection control device is characterized in that the in-cylinder injection determining means determines that the in-cylinder injection is determined when the end of the basic in-cylinder injection is determined to be behind the end of the valve opening period of the intake valve. The end of the valve opening period (instead of the basic in-cylinder injection end) is determined to be a timing that is more advanced than the basic in-cylinder injection end, and the in-cylinder injection amount is set to the basic in-cylinder injection amount. Instead, the port injection determining means is configured to determine an amount that is smaller by a predetermined amount than the basic in-cylinder injection amount, and the port injection determining means is configured such that the basic in-cylinder injection end is later than the end of the intake valve opening period. When it is determined that the angle is on the corner side, the port injection amount is determined to be larger than the basic port injection amount by the predetermined amount (instead of the basic port injection amount).

  Here, when it is determined that the end of the basic in-cylinder injection is retarded from the end of the valve opening period of the intake valve, the start of the opening timing of the in-cylinder injection valve is (the basic in-cylinder injection start Instead of the basic in-cylinder injection start time, it may be determined at an advance timing side. Further, the end of the opening timing of the in-cylinder injection valve determined as described above may be a timing retarded from the end of the opening period of the intake valve, or the end of the opening period of the intake valve. It may be a more advanced time than the end.

  According to the above configuration, the extent to which the end of the valve opening period of the in-cylinder injection valve is retarded relative to the end of the valve opening period of the intake valve can be reduced. Therefore, the amount of “difficult to mix” fuel among the fuels produced by in-cylinder injection can be suppressed. Further, the in-cylinder injection amount is determined to be a predetermined amount smaller than the basic in-cylinder injection amount. That is, the in-cylinder injection period can be shorter than that corresponding to the basic in-cylinder injection amount. For this reason, even if the end of the opening period of the in-cylinder injection valve is determined at a timing that is more advanced than the end of the basic in-cylinder injection, the start of the opening period of the in-cylinder injection valve is set to The degree of advance side can be made as small as possible. Therefore, the extent to which the start of the valve opening period of the in-cylinder injection valve is advanced from the end of the valve opening period of the exhaust valve can be suppressed.

  In addition, the port injection amount is determined to be larger than the basic port injection amount by the predetermined amount. Accordingly, the amount of fuel that is “difficult to mix” can be suppressed without changing the total fuel injection amount (that is, the sum of the basic port injection amount and the basic in-cylinder injection amount). Can be suppressed.

  Specifically, in this fuel injection control device, for example, the in-cylinder injection determining means determines that the basic in-cylinder injection end is on the more retarded side than the end of the intake valve opening period. The start period of the in-cylinder injection valve is maintained at the basic in-cylinder injection start period, and the end of the in-cylinder injection valve opening period is determined to be equal to the end of the intake valve opening period. The in-cylinder injection amount is determined to be smaller than the basic in-cylinder injection amount by an amount corresponding to the interval between the basic in-cylinder injection end and the end of the intake valve opening period. When the port injection determining means determines that the basic in-cylinder injection end is on the more retarded side than the end of the intake valve opening period, the port injection amount is set to be greater than the basic port injection amount. An amount that is larger by an amount corresponding to the interval is determined.

  In particular, at the time of high load / high rotation operation, the degree to which the basic in-cylinder injection end is retarded from the end of the intake valve opening period tends to be large. Therefore, it is considered that there is a great demand for suppressing the amount of “difficult to mix” fuel during high load / high rotation operation. According to the above configuration, without changing the total amount of fuel injection, it is possible to avoid the end of the in-cylinder injection period from being retarded from the end of the intake valve opening period. “The amount of fuel can be zero. Therefore, even during high-load / high-speed operation, the amount of “difficult to mix” fuel can be reliably suppressed, and the degree of reduction in engine output can be reliably suppressed.

  In addition, by determining the basic in-cylinder injection start time, for example, at a timing retarded from the end of the exhaust valve opening period, the in-cylinder injection is reliably performed after the end of the exhaust valve opening period. Can be started. In addition, the in-cylinder injection amount from the basic in-cylinder injection amount is larger than when the end of the in-cylinder injection valve opening period is determined to be advanced from the end of the intake valve opening period. The degree of reduction can be small. Therefore, the degree of cooling effect reduction by in-cylinder injection can also be reduced.

  In the fuel injection control device, the port injection determining means may determine that the basic in-cylinder injection end is determined to be retarded from the end of the intake valve opening period, and When it is determined that the absolute value of the change rate of the port injection amount is greater than the predetermined change rate, the port injection amount is set to be smaller than the basic port injection amount so that the absolute value of the change rate matches the predetermined change rate. And the in-cylinder injection determining means is configured so that the basic in-cylinder injection end time is more retarded than the end of the intake valve opening period. And when it is determined that the absolute value of the change rate of the port injection amount is greater than the predetermined change rate, the in-cylinder injection amount is set to be greater than the basic in-cylinder injection amount. Only the amount corresponding to the interval Instead of the old amount) than the basic cylinder injection amount, it may be configured to determine only a small amount the amount obtained by subtracting the base port injection quantity from port injection amount the determined.

  In the present specification, the change rate of the port injection amount is a value that becomes a larger positive value as the increase rate of the port injection amount is larger, and is a negative value that is smaller as the decrease rate of the port injection amount is larger. It is assumed that

  In general, part of the fuel injected from the port injection valve adheres to the intake system (the wall surface of the intake pipe, the umbrella portion of the intake valve, etc.). Therefore, in the intake passage, the fuel that is injected from the port injection valve and does not adhere to the intake system and the fuel evaporated from the attached fuel flow into the cylinder. On the other hand, as the port injection amount increases (decreases), the amount of fuel attached to the intake system tends to increase (decrease) with respect to the port injection amount. Therefore, when the port injection amount increases (decreases), the amount of fuel flowing into the cylinder becomes smaller (larger) than the amount of fuel for obtaining the target air-fuel ratio, and the air-fuel ratio is leaner than the target air-fuel ratio. There is a tendency to easily shift in the (rich direction). The degree of deviation of the air-fuel ratio from the target air-fuel ratio becomes larger as the absolute value of the change rate of the port injection amount is larger.

  Here, when it is determined that the end of the basic in-cylinder injection is more retarded than the end of the intake valve opening period, the port injection amount and When the in-cylinder injection amount is determined, the absolute value of the change rate of the port injection amount may increase. In this case, a situation may occur in which the degree of deviation of the air-fuel ratio from the target air-fuel ratio becomes large. From the viewpoint of suppressing the degree of deviation of the air-fuel ratio from the target air-fuel ratio, it is preferable to determine the port injection amount and the in-cylinder injection amount so that the absolute value of the change rate of the port injection amount does not become a large speed. .

  The said structure is based on this knowledge. According to this, the predetermined change speed is set to an absolute value of the change speed of the port injection amount corresponding to, for example, a case where the degree of deviation of the air-fuel ratio from the target air-fuel ratio is within the appropriate range. obtain. Therefore, an increase in the absolute value of the change rate of the port injection amount can be suppressed, and the degree of deviation of the air-fuel ratio from the target air-fuel ratio can be suppressed.

  In the fuel injection control device, the port injection determining means may determine that the basic in-cylinder injection end is determined to be retarded from the end of the intake valve opening period, and When it is determined that the decrease rate of the port injection amount is greater than the predetermined decrease rate, the port injection amount is determined so that the decrease rate matches the predetermined decrease rate, and the in-cylinder injection determining means When it is determined that the basic in-cylinder injection end time is retarded from the end of the intake valve opening period, it is determined that the reduction rate of the port injection amount is greater than the predetermined reduction rate. In this case, the in-cylinder injection amount may be determined to be smaller than the basic in-cylinder injection amount by an amount obtained by subtracting the basic port injection amount from the determined port injection amount. .

  It is a case where it is determined that the basic in-cylinder injection end is on the retard side with respect to the end of the intake valve opening period, for example, the increasing speed of the port injection amount (corresponding to the predetermined change speed) When it is determined that the speed is higher than the predetermined increase speed, the problem described below occurs when the increase speed is limited to a small speed. In this case, the degree of decrease in the in-cylinder injection amount from the basic in-cylinder injection amount may be reduced, and a situation may occur in which it is difficult to sufficiently suppress the amount of “difficult to mix” fuel (right in FIG. 4). (See the shaded area above.) In this case, it is preferable not to limit the increasing speed of the port injection amount from the viewpoint of avoiding such a situation.

  On the other hand, when it is determined that the basic in-cylinder injection end time is retarded from the end of the intake valve opening period, the rate of decrease in the port injection amount (corresponding to the predetermined change speed) When it is determined that the decrease rate is greater than the predetermined decrease rate, even if the decrease rate is limited to a small rate, the amount of “unmixable” fuel can be sufficiently suppressed. Therefore, in this case, it is preferable to limit the decrease rate of the port injection amount. The said structure is based on this knowledge. According to this, the amount of fuel that is “difficult to mix” in the fuel by in-cylinder injection can be sufficiently suppressed, and the degree of shift of the air-fuel ratio from the target air-fuel ratio in the rich direction can be suppressed.

  Embodiments of a fuel injection control device for an internal combustion engine according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of a system in which a fuel injection control device according to a first embodiment of the present invention is applied to a spark ignition type multi-cylinder (four-cylinder) internal combustion engine 10 having a dual injection system. The internal combustion engine 10 includes a cylinder block unit 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head unit 30 fixed on the cylinder block unit 20, and a gasoline mixture in the cylinder block unit 20. And an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft that drives the intake valve 32, and a phase angle of the intake camshaft (ie, intake valve) The variable intake timing device 33 that continuously changes the open / close timing of the engine 32 according to the operating state of the engine, the actuator 33a of the variable intake timing device 33, the exhaust port 34 that communicates with the combustion chamber 25, and the exhaust that opens and closes the exhaust port 34 A valve 35, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37, an igniter 38 that includes an ignition coil that generates a high voltage applied to the ignition plug 37, a port injection valve 39 </ b> P that injects fuel into the intake port 31, An in-cylinder injection valve 39C for directly injecting fuel into the combustion chamber 25 is provided. There.

  The intake system 40 is provided in an intake pipe 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and the intake pipe 41. A throttle valve 43 for changing the opening cross-sectional area of the intake passage and a throttle valve actuator 43a made of a DC motor are provided.

  The exhaust system 50 includes an exhaust manifold 51 that communicates with the exhaust port 34, and an exhaust pipe (exhaust pipe) that is connected to the exhaust manifold 51 (actually, a collection portion of the exhaust manifolds 51 that communicate with each exhaust port 34). ) 52, and a three-way catalyst 53 disposed (intervened) in the exhaust pipe 52. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, a cam position sensor 62, a crank position sensor 63, a water temperature sensor 64, and an exhaust passage upstream of the three-way catalyst 53 (in this example, a set in which the exhaust manifolds 51 are gathered. The air-fuel ratio sensor 65 is provided.

  The hot-wire air flow meter 61 detects the mass flow rate of the intake air flowing through the intake pipe 41 per unit time and outputs a signal representing the intake air flow rate Ga. The cam position sensor 62 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °). This signal represents the opening / closing timing of the intake valve 32. The crank position sensor 63 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °. This signal represents the operating speed NE. The water temperature sensor 64 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal representing the cooling water temperature THW. The air-fuel ratio sensor 65 outputs a current corresponding to the air-fuel ratio of the exhaust gas, and outputs a voltage corresponding to this current. From this output, the air-fuel ratio of the exhaust gas is calculated.

  The electric control device 70 includes a CPU 71 connected by a bus, a routine (program) executed by the CPU 71, a table (look-up table, map), a ROM 72 in which constants and the like are stored in advance, and the CPU 71 temporarily stores data as necessary. This is a microcomputer comprising a RAM 73 for storing data, a backup RAM 74 for storing data while the power is turned on and holding the stored data while the power is shut off, an interface 75 including an AD converter, and the like. .

  The interface 75 is connected to the sensors 61 to 65, supplies signals from the sensors 61 to 65 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, and the port injection valve 39P of the variable intake timing device 33. A drive signal is sent to the in-cylinder injection valve 39C and the throttle valve actuator 43a.

(Overview of fuel injection control)
Next, an outline of the fuel injection control performed by the fuel injection control device (hereinafter referred to as “this device”) according to the first embodiment configured as described above will be described.

  In this device, in principle, the port injection amount Fip and the in-cylinder are based on the basic injection ratio R (= (port injection amount Fip) / (port injection amount Fip + in-cylinder injection amount Fic), 0 ≦ R ≦ 1). The injection amount Fic is determined. In accordance with the determined port injection amount Fip and in-cylinder injection amount Fic, the respective valve opening periods of the port injection valve 39P and the in-cylinder injection valve 39C are set. Based on the operating state of the internal combustion engine 10, the set valve opening period, and the like, the start period CAsp and the end period CAep of the port injection valve 39P are calculated and determined, and the in-cylinder injection valve 39C is opened. The start CAsc and end CAec of the period are calculated and determined.

  In this device, when it is determined that the final CAec of the valve opening period of the in-cylinder injection valve 39C calculated and determined in this way is on the retard side with respect to the final IVC of the valve opening period of the intake valve 32, The in-cylinder injection amount Fic is re-determined so that the final CAec of the valve opening period of the inner injection valve is equal to the final IVC of the valve opening period of the intake valve 32. That is, in this case, the in-cylinder injection amount Fic is redetermined to an amount obtained by subtracting a predetermined amount from the in-cylinder injection amount Fic based on the basic injection ratio R.

  The determination of the in-cylinder injection amount Fic is based on the viewpoint described below. As described above, if the in-cylinder injection is continued even after the end IVC of the valve opening period of the intake valve 32, the gas flows into the combustion chamber 25 from the intake port 31 after the end IVC of the valve opening period of the intake valve 32. The fuel injected in-cylinder due to the failure is not mixed with fresh air. For this reason, the situation where the output of the internal combustion engine 10 falls may occur. Therefore, it is preferable that the in-cylinder injection is controlled so that the end CAec of the valve opening period of the in-cylinder injection valve 39C does not shift to the retard side than the end IVC of the valve opening period of the intake valve 32.

  On the other hand, there is a great demand for determining the start period CAsc of the in-cylinder injection valve 39C so that the in-cylinder injection is started at a timing retarded from the final EVC of the opening period of the exhaust valve 35. In particular, during a high load / high rotation operation, there is a great demand for determining the in-cylinder injection amount Fic as large as possible (that is, setting the valve opening period of the in-cylinder injection valve 39C as long as possible). From the above, the end CAec of the in-cylinder injection valve 39C corresponding to the in-cylinder injection amount Fic based on the basic injection ratio R is more retarded than the end IVC of the opening period of the intake valve 32. If it is determined, the in-cylinder injection amount Fic is re-determined so that the end CAec of the valve opening period of the in-cylinder injection valve 39C is equal to the end IVC of the valve opening period of the intake valve 32.

  On the other hand, the port injection amount Fip is redetermined to an amount obtained by adding the predetermined amount to the port injection amount Fip based on the basic injection ratio R. Thus, without changing the total fuel injection amount per cycle, the final CAec of the valve opening period of the in-cylinder injection valve 39C is not shifted to the retard side from the final IVC of the valve opening period of the intake valve 32. The internal injection can be controlled. The above is the outline of the fuel injection control performed by this apparatus.

(Actual operation)
Hereinafter, the actual operation of the present apparatus will be described with reference to the time chart shown in FIG. 2 and the flowchart shown in FIG.

  FIG. 2 is a time chart showing an example of changes in the accelerator pedal operation amount Accp, the port injection amount Fip, and the in-cylinder injection amount Fic when fuel injection control is performed by the present apparatus. Before the time t1, the manipulated variable Accp is maintained at the value Accp1, and at the time t1, the manipulated variable Accp is increased from the value Accp1 to the value Accp2 (> value Accp1). The manipulated variable Accp is maintained at the value Accp2 after time t1. Further, it is assumed that the manipulated variable Accp decreases from the value Accp2 to the value Accp1 at a time t2 when a sufficient time has elapsed from the time t1, and the manipulated variable Accp is maintained at the value Accp1 after the time t2.

  In this example, in order to facilitate the explanation, the in-cylinder intake air amount Mc also corresponds to the value Accp2 from the value Mc1 corresponding to the value Accp1 in accordance with the step change of the accelerator pedal operation amount Accp. It is assumed that the value Mc2 (> value Mc1) changes stepwise, and the total fuel injection amount per cycle (basic fuel injection amount Fbase described later) also changes stepwise accordingly.

  In addition, before and after time t1 and before and after time t2, the operation state of the internal combustion engine 10 is assumed to be an operation state (high load / high rotation operation state) in which the basic injection ratio R is determined to be zero. Prior to time t1 (after time t2), the end CAec of the valve opening period of the in-cylinder injection valve 39C corresponding to the in-cylinder injection amount Fic based on the basic injection ratio R is the end of the valve opening period of the intake valve 32. It is assumed that it will advance further than IVC. On the other hand, after the time t1 (before the time t2), it is assumed that the final CAec shifts more to the retard side than the final IVC.

  Hereinafter, for convenience of explanation, “MapX (a1, a2,...)” Represents a table for obtaining a value X having a1, a2,. Further, when the value of the argument is a detection value of the sensor, the current value is used.

  The CPU 71 repeatedly executes the routine for performing the fuel injection control shown in the flowchart of FIG. 3 every time the crank angle of each cylinder reaches a predetermined crank angle before each intake top dead center (for example, BTDC 90 ° CA). It has become. Therefore, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle, the CPU 71 starts the process from step 300 and proceeds to step 302, and uses the table MapMc (NE, Ga) to make the combustion chamber 25 in the intake stroke. An in-cylinder intake air amount Mc that is the amount of air sucked into the cylinder is calculated.

  Next, the CPU 71 proceeds to step 304 and obtains a value obtained by dividing the in-cylinder intake air amount Mc calculated in step 302 by the target air-fuel ratio abyfr (for example, the theoretical air-fuel ratio) set at the present time. The basic fuel injection amount Fbase is calculated by multiplying “Mc / abyfr” by the feedback coefficient K. That is, the basic fuel injection amount Fbase corresponds to the amount of fuel for obtaining the target air-fuel ratio abyfs with respect to the amount of air sucked into the combustion chamber 25 in the intake stroke. Here, as the feedback coefficient K, the latest value calculated by a routine not shown separately based on the output of the air-fuel ratio sensor 65 is used.

  Next, the CPU 71 proceeds to step 306 to calculate the basic injection ratio R using the table MapR (NE, Mc, THW). According to the table MapR (NE, Mc, THW), the basic injection ratio R is determined to be smaller as the operation speed NE is higher. This is because the rate of change of the volume of the combustion chamber 25 increases as the operating speed NE increases, so that the ratio of the in-cylinder injection amount Fic can be increased while suppressing the deterioration of the degree of mixing of fuel and fresh air by in-cylinder injection. Based on increasing degrees. The basic injection ratio R is determined to be smaller as the in-cylinder intake air amount Mc is larger and the cooling water temperature THW is higher. This is because knocking occurs because the gas pressure in the combustion chamber 25 increases as the cylinder intake air amount Mc increases, and the gas temperature in the combustion chamber 25 increases as the cooling water temperature THW increases. However, it is based on increasing the degree of cooling the gas in the combustion chamber 25 by increasing the ratio of the in-cylinder injection amount Fic and suppressing the occurrence of knocking.

  Subsequently, the CPU 71 proceeds to step 308 to determine the port based on the basic injection ratio R calculated in step 306, the basic fuel injection amount Fbase calculated in step 304, and the formula described in step 308. Determine the injection amount Fip. The port injection amount Fip determined in step 308 corresponds to the basic port injection amount.

  Next, the CPU 71 proceeds to step 310, and based on the basic injection ratio R calculated in step 306, the basic fuel injection amount Fbase calculated in step 304, and the formula described in step 310, the cylinder The internal injection amount Fic is determined. The in-cylinder injection amount Fic determined in step 310 corresponds to the basic in-cylinder injection amount.

  Next, the CPU 71 proceeds to step 312, and calculates the final CAep of the valve opening period of the port injection valve 39P. This final CAep is calculated based on the initial CAsp of the opening period of the port injection valve 39P and the port injection amount Fip determined in step 308. In this example, the start CAsp is set at a predetermined time in the latter half of the exhaust stroke, which is a time on the more advanced side than the start IVO of the valve opening period of the intake valve 32. When the start CAsp is maintained at a certain time, the end CAep is calculated at a more retarded time as the port injection amount Fip is larger. The start period CAsp and the end period CAep of the opening period of the port injection valve 39P correspond to the basic port injection start period and the basic port injection end period, respectively.

  Subsequently, the CPU 71 proceeds to step 314 to calculate the final CAec of the valve opening period of the in-cylinder injection valve 39C. The final CAec is calculated based on the initial CAsc of the valve opening period of the in-cylinder injection valve 39C and the in-cylinder injection amount Fic determined in step 310. In this example, the start CAsc is set at a predetermined time in the first half of the intake stroke, which is a time retarded from the end EVC of the valve opening period of the exhaust valve 35. When the start CAsc is maintained at a certain time, the end CAec is calculated at a more retarded time as the in-cylinder injection amount Fic is larger. The start period CAsc and the end stage CAec of the valve opening period of the in-cylinder injection valve 39C correspond to the basic in-cylinder injection start period and the basic in-cylinder injection end period, respectively.

  Next, the CPU 71 proceeds to step 316 to acquire the final IVC of the valve opening period of the intake valve 32. Here, as the final stage IVC, the latest value calculated by a routine not shown separately based on the operating speed NE, the in-cylinder intake air amount Mc, and the like is used.

  Subsequently, the CPU 71 proceeds to step 318, where the end CAec of the opening period of the in-cylinder injection valve 39C calculated in step 314 is from the end IVC of the opening period of the intake valve 32 acquired in step 316. It is also determined whether or not the angle is on the advance side. When the CPU 71 determines “Yes” in step 318, the CPU 71 immediately proceeds to step 395 and once ends this routine.

  Before time t1 in FIG. 2, “Yes” is determined in step 318. Therefore, the CPU 71 repeatedly executes the processes of steps 302 to 318 and 395. As a result, before time t1, the basic fuel injection amount Fbase is determined to be the value Fbase1 corresponding to the case where the accelerator pedal operation amount Accp is the value Accp1 (corresponding to the value Mc1) in step 304. In step 306, the basic injection ratio R is calculated to be zero, and in steps 308 and 310, the port injection amount Fip and the in-cylinder injection amount Fic are determined to be zero and equal to the value Fbase1, respectively. That is, fuel injection of the basic fuel injection amount Fbase is achieved only by in-cylinder injection. In this case, the final CAec of the valve opening period of the in-cylinder injection valve 39C is more advanced than the final IVC of the valve opening period of the intake valve 32. Therefore, the fuel injected into the cylinder after the final IVC The amount of (i.e. the “unmixable” fuel) is zero. Therefore, a situation in which the degree of mixing of fuel and fresh air due to in-cylinder injection deteriorates can be avoided.

  When time t1 in FIG. 2 arrives, in step 304, the basic fuel injection amount Fbase corresponds to a value Fbase2 (corresponding to the value Mc2 (> value Mc1)) corresponding to the case where the accelerator pedal operation amount Accp is the value Accp2. > Value Fbase1). Accordingly, in step 310, the in-cylinder injection amount Fic is determined to be the above-described value Fbase2, and in step 314, the end CAec of the opening period of the in-cylinder injection valve 39C is delayed from the end IVC of the opening period of the intake valve 32. It is calculated at the time of the side.

  Therefore, the CPU 71 that has repeatedly executed the above processing determines “No” when the process proceeds to step 318, and proceeds to step 320. The CPU 71 proceeds to step 320, and the valve opening period of the intake valve 32 obtained in step 316 from the final CAec (corresponding to the crank angle) of the valve opening period of the in-cylinder injection valve 39C calculated in step 314. The crank angle difference ΔCA obtained by subtracting the final IVC (the corresponding crank angle) is calculated. In this specification, it is assumed that the crank angle is larger as the crank angle is on the retard side.

  Next, the CPU 71 proceeds to step 322 to calculate the crank angle difference equivalent injection amount ΔFi using the table MapΔFi (NE, ΔCA). According to the table MapΔFi (NE, ΔCA), the crank angle difference equivalent injection amount ΔFi is calculated to be larger as the crank angle difference calculated in step 320 is larger. Further, the crank angle difference equivalent injection amount ΔFi is calculated to be larger as the operating speed NE is smaller. This is based on the fact that the time interval per unit crank angle is longer as the operating speed NE is smaller. This crank angle difference equivalent injection amount ΔFi corresponds to the “amount corresponding to the interval between the end of the basic in-cylinder injection and the end of the intake valve opening period”, and the amount of fuel that is difficult to be mixed as described above. It corresponds to.

  Next, the CPU 71 proceeds to step 324 to reset the port injection amount Fip to an amount obtained by adding the crank angle difference equivalent injection amount ΔFi calculated in step 322 to the port injection amount Fip determined in step 308. decide.

  Subsequently, the CPU 71 proceeds to step 326 to obtain the in-cylinder injection amount Fic by subtracting the crank angle difference equivalent injection amount ΔFi calculated in step 322 from the in-cylinder injection amount Fic determined in step 310. Redetermine to quantity.

  Next, the CPU 71 proceeds to step 328 and obtains the final CAep of the opening period of the port injection valve 39P by adding the crank angle difference ΔCA calculated in step 320 to the final CAep calculated in step 312. The time corresponding to the value (that is, the time delayed by the crank angle difference ΔCA from the final CAep calculated in step 312) is reset. Note that the start CAsp of the opening period of the port injection valve 39P is not reset, and is maintained at a predetermined timing in the latter half of the exhaust stroke, which is a time advanced from the start IVO of the opening period of the intake valve 32. Is done. Steps 308, 312, 318, 324, and 328 correspond to a part of the port injection determining means.

  Next, the CPU 71 proceeds to step 330 to set the final CAec of the valve opening period of the in-cylinder injection valve 39C to the final CAec calculated in step 314 of the valve opening period of the intake valve 32 acquired in step 316. Reset to the same time as the final IVC. Note that the start CAsc of the opening period of the in-cylinder injection valve 39C is not reset, and is a timing retarded from the end EVC of the opening period of the exhaust valve 35, and at a predetermined time in the first half of the intake stroke. Maintained. Then, the CPU 71 proceeds to step 395 to end this routine once. Steps 310, 314, 318, 326, and 330 correspond to a part of the in-cylinder injection determining means.

  After time t1 in FIG. 2, the CPU 71 repeatedly executes the processes of steps 302 to 318 and 320 to 395. As a result, after time t1, the port injection amount Fip is determined to be zero at step 308 and then re-determined to an amount equal to the crank angle difference equivalent injection amount ΔFi at step 324. The in-cylinder injection amount Fic is determined to be equal to the value Fbase2 in step 310, and is then determined again in step 326 to an amount obtained by subtracting the crank angle difference equivalent injection amount ΔFi from the value Fbase2.

  That is, the amount of fuel corresponding to the hatched portion of FIG. 2 in the value Fbase2 is the amount of fuel injected into the cylinder after the end IVC of the valve opening period of the intake valve 32 (that is, the “mixing” Corresponding to “difficult” fuel). The amount of fuel corresponding to the hatched portion is transferred from the in-cylinder injection amount Fic to the port injection amount Fip, so that the fuel injection of the value Fbase2 is performed between the injection from the in-cylinder injection valve 39C and the port. This is achieved by injection from the injection valve 39P.

  Further, the end CAec of the valve opening period of the in-cylinder injection valve 39C is set to a time equal to the end IVC of the valve opening period of the intake valve 32. From the above, the amount of fuel that is injected into the cylinder after the end IVC of the valve opening period of the intake valve 32 (that is, the above-mentioned “difficult to mix” fuel) can be zero. Therefore, a situation in which the degree of mixing of fuel and fresh air due to in-cylinder injection deteriorates can be avoided.

  When time t2 in FIG. 2 has arrived, the CPU 71 that has repeatedly executed the above processing determines “Yes” when it proceeds to step 318, and immediately proceeds to step 395. After time t2, before time t1 Similarly, the CPU 71 repeatedly executes the processes of steps 302 to 318 and 395. As a result, after time t2, the port injection amount Fip and the in-cylinder injection amount Fic are determined to be zero and the value Fbase1 in steps 308 and 310, respectively. In this case as well, the final CAec of the valve opening period of the in-cylinder injection valve 39C is more advanced than the final period IVC of the valve opening period of the intake valve 32. Therefore, the degree of mixing of fuel and fresh air by in-cylinder injection The situation where it gets worse can be avoided.

  As described above, according to the fuel injection control device according to the first embodiment, the in-cylinder injection valve 39C corresponding to the in-cylinder injection amount Fic (= (1−R) · Fbase) based on the basic injection ratio R. When it is determined that the final CAec of the valve opening period is more retarded than the final IVC of the valve opening period of the intake valve 32, the final CAec of the valve opening period of the in-cylinder injection valve 39C is equal to the final IVC. At the same time, the in-cylinder injection amount Fic is re-determined to be smaller than the in-cylinder injection amount Fic based on the basic injection ratio R by the crank angle difference equivalent injection amount ΔFi. Therefore, the situation where the mixing degree of the fuel and the fresh air by the in-cylinder injection is deteriorated as described above can be avoided.

  Further, the port injection amount Fip is redetermined to an amount larger than the port injection amount Fip (= R · Fbase) based on the basic injection ratio R by the crank angle difference equivalent injection amount ΔFi. Accordingly, the total fuel amount per cycle is maintained equal to the basic fuel injection amount Fbase. From the above, it is possible to avoid a situation in which the output of the internal combustion engine 10 decreases.

  In addition, the start period CAsc of the opening period of the in-cylinder injection valve 39C is always a timing retarded from the end EVC of the opening period of the exhaust valve 35, and is maintained at a predetermined period in the first half of the intake stroke. The Therefore, in-cylinder injection can be surely started after the final EVC. Furthermore, the in-cylinder injection amount Fic re-determined as compared with the case where the end CAec of the valve opening period of the in-cylinder injection valve 39C is reset to the advance side with respect to the end IVC of the valve opening period of the intake valve 32. The degree of decrease from the above value “(1−R) · Fbase” can be reduced. Therefore, it is possible to reduce the degree of decrease in the cooling effect due to the in-cylinder injection while reducing the amount of the “difficult to mix” fuel to zero.

  The present invention is not limited to the first embodiment, and various modifications can be employed within the scope of the present invention. For example, in the first embodiment, when it is determined that the condition described in step 318 is not satisfied, the final CAC of the valve opening period of the in-cylinder injection valve 39C is the final IVC of the valve opening period of the intake valve 32. However, instead of this, it may be reset to a timing on the more advanced side than the final stage IVC of the valve opening period of the intake valve 32. The end CAec of the valve opening period of the in-cylinder injection valve 39C is within the range of the crank angle that is advanced from the end CAec calculated in step 314, and from the end IVC of the valve opening period of the intake valve 32. Also, it may be reset to the retarded time.

(Second Embodiment)
Next, a fuel injection control device according to a second embodiment of the present invention will be described. In the second embodiment, when it is determined that the absolute value of the change rate of the port injection amount Fip is larger than the upper limit change rate that should not be exceeded, the absolute value of the change rate of the port injection amount Fip matches the upper limit change rate. Thus, the port injection amount Fip and the in-cylinder injection amount Fic are determined again. The second embodiment is different from the first embodiment only in this point.

  The reason for determining the port injection amount Fip and the in-cylinder injection amount Fic in this way will be described. As described above, when the port injection amount Fip increases (decreases), the amount of fuel attached to the intake system (the wall surface of the intake pipe 41, the umbrella portion of the intake valve 32, etc.) with respect to the port injection amount Fip increases (decreases). As a result, the air-fuel ratio tends to easily shift in the lean direction (rich direction) with respect to the target air-fuel ratio abyfr. The degree of deviation of the air-fuel ratio from the target air-fuel ratio abyfr increases as the absolute value of the change speed of the port injection amount Fip increases. Therefore, it is preferable that the port injection amount Fip and the in-cylinder injection amount Fic are determined so that the absolute value of the change speed of the port injection amount Fip does not become a large speed.

  Based on this knowledge, in this example, the upper limit speed of the change speed of the port injection amount Fip is the change speed corresponding to the case where the degree of deviation of the air-fuel ratio from the target air-fuel ratio abyfr is within the appropriate range. Set to an absolute value. As a result, the degree of deviation of the air / fuel ratio from the target air / fuel ratio abyfr can be suppressed. The above is the reason for limiting the changing speed of the port injection amount Fip.

  Hereinafter, only the differences of the second embodiment from the first embodiment will be described with reference to the time chart of FIG. 4 corresponding to FIG. 2 and the flowcharts of FIGS. 5 and 6 corresponding to FIG. Times t1 and t2 in FIG. 4 correspond to times t1 and t2 in FIG. Further, the CPU 71 of the fuel injection control device according to the second embodiment executes a series of routines shown in the flowcharts of FIGS. 5 and 6 in place of the routine of FIG. In the series of routines shown in FIG. 5 and FIG. 6, the same steps as those in the routine of FIG.

  The series of routines shown in FIGS. 5 and 6 differ from the routine of FIG. 3 only in that steps 502 to 512 are added to the routine of FIG. In step 502, the absolute value of a value obtained by subtracting the port injection amount previous value Fipb updated in step 512, which will be described later at the time of the previous execution of this routine, from the port injection amount Fip determined in step 308 or step 324, It is determined whether or not it is larger than the port injection amount upper limit change amount ΔFipth. Here, the port injection amount upper limit change amount ΔFipth is an absolute value of the change amount of the port injection amount Fip with respect to the execution interval of this routine, which is set so as to correspond to the upper limit change speed. This port injection amount upper limit change amount ΔFipth is set to a smaller value because the execution interval of this routine is smaller as the operating speed NE is larger.

  When it is determined as “Yes” in Step 502, the processes of Steps 504 to 512 are executed in order. In step 504, the port injection amount Fip is determined again based on the formula described in step 504. Here, sgn (Fip−Fipb) is a sine function that becomes “1”, “−1”, and “0” when the value “Fip−Fipb” is a positive value, a negative value, and zero, respectively. (Sign function).

  In step 506, the in-cylinder injection amount Fic is determined to be a value obtained by subtracting the port injection amount Fip redetermined in step 504 from the basic fuel injection amount Fbase calculated in step 304. In step 508, the start CAsp of the opening period of the port injection valve 39P and the end CAep of the opening period of the port injection valve 39P are calculated and reset based on the port injection amount Fip re-determined in step 504. . In step 510, the start CAsc of the opening period of the in-cylinder injection valve 39C and the end CAec of the opening period of the in-cylinder injection valve 39C are calculated and re-calculated based on the in-cylinder injection amount Fic re-determined in step 506. Is set.

  Also in this example, the start periods CAsp and CAsc of the valve opening period of the port injection valve 39P and the in-cylinder injection valve 39C are not reset, and are more advanced than the start period IVO of the opening period of the intake valve 32. The timing is maintained at a predetermined timing in the second half of the exhaust stroke and a predetermined timing in the first half of the intake stroke, which is a timing retarded from the final EVC of the valve opening period of the exhaust valve 35.

  In step 512, the port injection amount previous value Fipb is updated to the port injection amount Fip determined again in step 504. If “No” is determined in step 502, the process of step 512 is immediately executed. In this case, in step 512, the port injection amount previous value Fipb is updated to the port injection amount Fip determined in step 308 or step 324. Steps 308, 312, 318, 324, 328, 502, 504, and 508 correspond to a part of the port injection determining means. Steps 310, 314, 318, 326, 330, 502, 506, 510 correspond to a part of the in-cylinder injection determining means.

  Before time t1 in FIG. 4, it is determined as “Yes” in step 318, and it is determined whether or not the condition in step 502 is satisfied. In this case, since the port injection amount Fip and the port injection amount previous value Fipb determined in step 308 are zero, “No” is determined in step 502. In step 512, the previous port injection amount value Fipb is updated to zero. That is, the CPU 71 according to the second embodiment repeatedly executes the processes of steps 302 to 318, 502, 512, and 595. As a result, before the time t1, the port injection amount Fip and the in-cylinder injection amount Fic are maintained at zero and the value Fbase1.

  When the time t1 in FIG. 4 arrives, the CPU 71 that has repeatedly executed the above processing determines “No” when it proceeds to step 318, proceeds to steps 320 to 330 in order, and then proceeds to step 502. . In this case, since the port injection amount Fip determined in step 324 is equal to the value ΔFi, the absolute value of the value “Fip (= ΔFi) −Fipb (= 0)” is the upper limit change of the port injection amount. It becomes a positive value larger than the amount ΔFipth. Therefore, it is determined as “Yes” in Step 502, and the processing after Step 504 is executed. At time t1, since the port injection amount Fip is zero, the in-cylinder injection amount Fic is determined to be equal to the value Fbase2 (see step 506). The value “Fbase−Fip” in step 506 corresponds to “an amount smaller than the basic in-cylinder injection amount by an amount obtained by subtracting the basic port injection amount from the determined port injection amount”.

  After time t1, the CPU 71 repeatedly executes the processes of steps 302 to 318, 320 to 330, 502, and 504 to 595. As a result, the port injection amount Fip is redetermined to the value “Fipb + ΔFipth” (see step 504). Thereby, the port injection amount Fip increases from zero toward the value ΔFi with a delay with respect to the stepwise increase in the port injection amount Fip (see the broken line in FIG. 4) in the first embodiment. On the other hand, the in-cylinder injection amount Fic decreases from the value Fbase2 toward the value “Fbase2−ΔFi”. That is, with respect to the first embodiment, in the present example, the amount of fuel corresponding to the portion indicated by the upward-sloping diagonal line in FIG. 4 is transferred from the port injection amount Fip to the in-cylinder injection amount Fic. The increasing speed of the port injection amount Fip can coincide with the upper limit changing speed. Therefore, the degree of deviation of the air-fuel ratio from the target air-fuel ratio abyfr in the lean direction can be suppressed. On the other hand, the value “Fip (= ΔFi) −Fipb” also decreases as the port injection amount previous value Fipb updated in step 512 increases after time t1.

  When the absolute value of the value “Fip (= ΔFi) −Fipb” becomes equal to or smaller than the port injection amount upper limit change amount ΔFipth and time t3 in FIG. 4 arrives, the CPU 71 that has repeatedly executed the above processing proceeds to step 502 At that time, it is determined as “No”, and the process immediately proceeds to step 512. Accordingly, the port injection amount Fip is determined to be equal to the value ΔFi. Further, the in-cylinder injection amount Fic is determined to be equal to the value “Fbase2−ΔFi”. After time t3, the CPU 71 repeatedly executes the processing of steps 302 to 318, 320 to 330, 502, 512, and 595. As a result, the port injection amount Fip and the in-cylinder injection amount Fic are maintained at the value ΔFi and the value “Fbase2−ΔFi”, respectively.

  When the time t2 in FIG. 4 arrives, the CPU 71 that has repeatedly executed the above processing determines “Yes” when it proceeds to step 318, and proceeds to step 502. In this case, since the port injection amount Fip determined in step 308 is zero, the value “Fip (= 0) −Fipb (= ΔFi)” has an absolute value larger than the port injection amount upper limit change amount ΔFipth. Negative value. Therefore, it is determined as “Yes” in Step 502, and the processing after Step 504 is executed. At time t2, since the port injection amount Fip is the value ΔFi, the in-cylinder injection amount Fic is determined to be equal to the value “Fbase1−ΔFi” (see step 506).

  After time t2, the CPU 71 repeatedly executes the processes of steps 302 to 318, 320 to 330, 502, and 504 to 595. As a result, the port injection amount Fip is redetermined to the value “Fipb−ΔFipth” (see step 504). Thus, the port injection amount Fip decreases from the value ΔFi toward zero with a delay with respect to the stepwise decrease in the port injection amount Fip (see the broken line in FIG. 4) in the first embodiment. On the other hand, the in-cylinder injection amount Fic increases from the value “Fbase1−ΔFi” toward the value Fbase1. That is, with respect to the first embodiment, in this example, the amount of fuel corresponding to the portion indicated by the left-upward oblique line in FIG. 4 is transferred from the in-cylinder injection amount Fic to the port injection amount Fip. The decreasing speed of the port injection amount Fip can coincide with the upper limit changing speed. Therefore, the degree of deviation of the air-fuel ratio from the target air-fuel ratio abyfr in the rich direction can be suppressed. On the other hand, the value “Fip (= 0) −Fipb” also increases as the port injection amount previous value Fipb updated in step 512 decreases after time t2.

  When the absolute value of the value “Fip (= 0) −Fipb” becomes equal to or smaller than the port injection amount upper limit change ΔFipth and time t4 in FIG. 4 arrives, the CPU 71 that has repeatedly executed the processing proceeds to step 502. At that time, it is determined as “No”, and the process immediately proceeds to step 512. Therefore, the port injection amount Fip is determined to be zero. Further, the in-cylinder injection amount Fic is determined to be equal to the value Fbase1. After time t4, the CPU 71 repeatedly executes the processes of steps 302 to 318, 502, 512, and 595. As a result, the port injection amount Fip and the in-cylinder injection amount Fic are maintained at zero and the value Fbase1, respectively.

  As described above, according to the fuel injection control device according to the second embodiment, when it is determined that the absolute value of the change speed of the port injection amount Fip is larger than the upper limit speed, the change of the port injection amount Fip. The port injection amount Fip and the in-cylinder injection amount Fic are redetermined so that the absolute value of the speed matches the upper limit speed. Therefore, the degree of deviation of the air / fuel ratio from the target air / fuel ratio abyfr can be suppressed.

  Further, according to the second embodiment, the final CAec of the valve opening period of the in-cylinder injection valve 39C related to the in-cylinder injection amount Fic (= (1-R) · Fbase) based on the basic injection ratio R is the intake valve 32. Of the valve opening period is determined to be retarded from the final IVC, and when the increase rate of the port injection amount Fip is determined to be greater than the upper limit speed, the port injection amount Fip is delayed. As the fuel flow increases, the amount of fuel injected into the cylinder after the final stage IVC (that is, the fuel that is difficult to be mixed) also decreases toward zero with a delay (indicated by the upward-sloping diagonal line in FIG. 4). See the part shown). Therefore, for example, even when it is determined that the final CAec is more retarded than the final IVC, the final CAec of the valve opening period of the in-cylinder injection valve 39C is maintained at the same time (for example, Compared to the broken line in FIG. 2), it is possible to suppress the deterioration of the degree of mixing of fuel and fresh air by in-cylinder injection.

  The present invention is not limited to the second embodiment, and various modifications can be adopted within the scope of the present invention. For example, in the second embodiment, when it is determined that the absolute value of the change speed of the port injection amount Fip is larger than the upper limit speed, the port is set so that both the increase speed and the decrease speed coincide with the upper limit speed. Although the injection amount Fip has been determined, instead of this, if it is determined as described above, the port injection amount Fip may be determined without matching the increase speed with the upper limit speed only and limiting the decrease speed. .

(Third embodiment)
Next, a fuel injection control apparatus according to a third embodiment of the present invention will be described. In the third embodiment, when it is determined that the final CAec of the valve opening period of the in-cylinder injection valve 39C is more retarded than the final IVC of the valve opening period of the intake valve 32, the port injection amount Fip increases. When there is a tendency, the port injection amount Fip and the in-cylinder injection amount Fic are determined without limiting the increasing speed of the port injection amount Fip. The third embodiment is different from the second embodiment only in this point.

  That is, in the third embodiment, when it is determined that the final CAec is on the more advanced side than the final IVC, it is determined that the absolute value of the changing speed of the port injection amount Fip is larger than the upper limit speed. The port injection amount Fip and the in-cylinder injection amount Fic are redetermined so that the absolute value of the change speed of the port injection amount Fip matches the upper limit speed. Further, when it is determined that the end CAec is more retarded than the end IVC, and it is determined that the decrease rate of the port injection amount Fip is larger than the upper limit speed, the port injection amount Fip The port injection amount Fip and the in-cylinder injection amount Fic are redetermined so that the decreasing speed matches the upper limit speed.

  The reason for determining the port injection amount Fip and the in-cylinder injection amount Fic in this way will be described. In the second embodiment, when it is determined that the final CAec is more retarded than the final IVC, and when the increase rate of the port injection amount Fip is determined to be greater than the upper limit speed, While the increase speed of the port injection amount Fip is limited, the amount of fuel injected into the cylinder after the end IVC is temporarily increased to a value larger than zero (indicated by time t1 in FIG. See below). That is, it is difficult for the amount of fuel injected into the cylinder after the final IVC to become zero immediately. Therefore, although the degree of deviation of the air-fuel ratio from the target air-fuel ratio abyfr in the lean direction can be suppressed, it is difficult to reliably suppress the deterioration of the degree of mixing of fuel and fresh air due to in-cylinder injection.

  In order to maintain priority on keeping the amount of fuel injected in the cylinder after the above-mentioned final IVC to zero and reliably suppressing the deterioration of the mixing degree, in the above-described case, the increase rate of the port injection amount Fip is set to It is preferable not to limit.

  On the other hand, in the case where it is determined that the end CAec is more retarded than the end IVC and the port injection amount Fip tends to increase, in-cylinder injection is performed after the end IVC. The amount of fuel can be maintained at zero. Therefore, in this case, it is preferable to limit the absolute value of the change speed of the port injection amount Fip in order to suppress the degree of deviation of the air / fuel ratio from the target air / fuel ratio abyfr. The above is the reason for determining the port injection amount Fip and the in-cylinder injection amount Fic as described above.

  Hereinafter, only differences of the third embodiment from the second embodiment will be described with reference to the time chart of FIG. 7 corresponding to FIG. 4 and the flowchart of FIG. 8 corresponding to FIG. Times t1, t2, and t4 in FIG. 7 correspond to times t1, t2, and t4 in FIG. Further, the CPU 71 of the fuel injection control device according to the third embodiment replaces the routine of FIG. 6 which is the latter half of the series of routines shown in FIGS. 5 and 6 with the routine shown in the flowchart of FIG. Run the routine. In FIG. 8, the same steps as those in the routine of FIG.

  The routine shown in FIG. 8 is such that steps 802 and 804 are added to the routine of FIG. 6, and if it is determined “No” in step 318, the processing of steps 502 and 504 is not executed. Only the routine of FIG. 6 is different. In step 802, the value obtained by subtracting the port injection amount Fip determined in step 324 from the port injection amount previous value Fipb updated in step 512 at the previous execution of this routine is the above-described port injection amount upper limit change amount ΔFipth. It is determined whether or not the value is greater than.

  When it is determined as “Yes” in Step 802, after the process of Step 804 is executed, the processes after Step 506 are executed. In step 804, the port injection amount Fip is determined to be an amount obtained by subtracting the port injection amount upper limit change amount ΔFipth from the port injection amount previous value Fipb.

  If “No” is determined in step 802, the process of step 512 is immediately executed. In this case, in step 512, the port injection amount previous value Fipb is updated to the port injection amount Fip determined in step 324. Steps 308, 312, 318, 324, 328, 502, 504, 508, 802, 804 correspond to a part of the port injection determining means. Steps 310, 314, 318, 326, 330, 502, 506, 510 correspond to a part of the in-cylinder injection determining means.

  When time t1 in FIG. 7 has arrived, the CPU 71 that has repeatedly executed the processing of steps 302 to 318, 502, 512, and 895 determines “No” when it proceeds to step 318, and proceeds to steps 320 to 330 in order. Thereafter, the process proceeds to step 802. In this case, since the port injection amount Fip determined in step 324 is equal to the value ΔFi, the value “Fipb (= 0) −Fip (= ΔFi)” is larger than the port injection amount upper limit change amount ΔFipth. Small negative value. Therefore, it is determined as “No” in Step 802, and the processing after Step 512 is executed. In step 512, the port injection amount previous value Fipb is updated to the port injection amount Fip (= ΔFi) determined in step 324. As a result, at time t1, the port injection amount Fip and the in-cylinder injection amount Fic are determined to the values ΔFi and “Fbase2−ΔFi” determined in steps 324 and 326, respectively.

  Since the value “Fipb−Fip” becomes zero after time t1, “No” is determined in step 802, and the CPU 71 repeatedly executes the processing of steps 302 to 318, 320 to 330, 802, 512, and 895. As a result, the port injection amount Fip and the in-cylinder injection amount Fic are maintained at the value ΔFi and the value “Fbase2−ΔFi”. That is, with respect to the second embodiment, in this example, the amount of fuel corresponding to the portion indicated by the diagonally upward slanted line in FIG. 7 is transferred from the in-cylinder injection amount Fic to the port injection amount Fip. Accordingly, the amount of fuel that is injected into the cylinder after the end IVC of the valve opening period of the intake valve 32 (that is, the above-mentioned “difficult to mix” fuel) is maintained at zero. As a result, deterioration of the degree of mixing of fuel and fresh air due to in-cylinder injection can be reliably suppressed.

  Further, after time t2, since the port injection amount Fip is determined so that the decreasing speed of the port injection amount Fip matches the upper limit speed, the target air-fuel ratio abyfr of the air-fuel ratio is determined from the same as in the second embodiment. The degree of shift in the rich direction can be suppressed.

  When it is determined as “Yes” in step 802 (that is, the end CAec of the opening period of the in-cylinder injection valve 39C calculated in step 314 is later than the end IVC of the opening period of the intake valve 32). When it is determined that the angle is on the corner side and the decrease rate of the port injection amount Fip is determined to be larger than the upper limit speed), the port injection amount Fip is re-determined to the value “Fipb−ΔFipth” in step 804. In step 506, the in-cylinder injection amount Fic is re-determined to the value “Fbase−Fip”. In this case, the redetermined port injection amount Fip is larger than the amount determined in step 324. Accordingly, the re-determined in-cylinder injection amount Fic is smaller than the amount determined in step 326.

  Therefore, in this case, the amount of fuel injected in-cylinder after the end stage IVC of the valve opening period of the intake valve 32 (that is, the “difficult to mix” fuel) is maintained at zero, while the port injection amount Fip The decreasing speed matches the upper limit speed. As a result, the deterioration of the degree of mixing of fuel and fresh air due to in-cylinder injection can be reliably suppressed, and the shift of the air-fuel ratio from the target air-fuel ratio in the rich direction can be suppressed.

  As described above, according to the fuel injection control device according to the third embodiment, the final CAec of the valve opening period of the in-cylinder injection valve 39C is on the more retarded side than the final IVC of the valve opening period of the intake valve 32. When it is determined that there is, the port injection amount Fip is determined so that the decrease rate of the port injection amount Fip matches the upper limit speed when it is determined that the decrease rate of the port injection amount Fip is greater than the upper limit speed. When it is not determined that the decreasing speed of the port injection amount Fip is larger than the upper limit speed, the port injection amount Fip is determined so that the changing speed of the port injection amount Fip is not limited.

  As a result, the in-cylinder injection amount Fic is determined to be an amount at which the amount of fuel injected into the cylinder after the final stage IVC of the valve opening period of the intake valve 32 (that is, the above-mentioned “difficult to mix” fuel) becomes zero. . As a result, deterioration of the degree of mixing of fuel and fresh air due to in-cylinder injection can be reliably suppressed. Further, the shift of the air-fuel ratio from the target air-fuel ratio in the rich direction can be suppressed.

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, in each of the above embodiments, the final port injection amount Fip and the in-cylinder injection amount Fic are redetermined instead of the port injection amount Fip and the in-cylinder injection amount Fic determined based on the basic injection ratio R. However, instead of this, instead of the basic injection ratio R, the ratio of the port injection amount Fip and the in-cylinder injection amount Fic is redetermined, so that the final port injection amount Fip and the in-cylinder injection amount Fic are It may be determined.

  In addition, in each of the above embodiments, the value “Fip / (Fip + Fic)” is adopted as the basic injection ratio R, but instead, the value “Fic / (Fip + Fic)” and the value “ "Fip / Fic", the value "Fic / Fip", etc. may be adopted.

1 is a schematic configuration of a system in which a fuel injection control device according to a first embodiment of the present invention is applied to a spark ignition type multi-cylinder internal combustion engine. 2 is a time chart showing an example of changes in an accelerator pedal operation amount, a port injection amount, and an in-cylinder injection amount when fuel injection control is performed by the fuel injection control device shown in FIG. 1. 2 is a flowchart showing a routine for performing fuel injection control executed by a CPU shown in FIG. It is the time chart which showed an example of the change of the operation amount of an accelerator pedal, the port injection amount, and the in-cylinder injection amount when fuel injection control is performed by the fuel injection control device according to the second embodiment of the present invention. It is the flowchart which showed the first half part of the routine for performing the fuel-injection control which CPU of the fuel-injection control apparatus which concerns on 2nd Embodiment of this invention performs. It is the flowchart which showed the second half part of the routine for performing the fuel-injection control which CPU of the fuel-injection control apparatus which concerns on 2nd Embodiment of this invention performs. It is the time chart which showed an example of the change of the operation amount of an accelerator pedal, the port injection amount, and the in-cylinder injection amount when fuel injection control is performed by the fuel injection control device according to the third embodiment of the present invention. It is the flowchart which showed the second half part of the routine for performing the fuel-injection control which CPU of the fuel-injection control apparatus which concerns on 3rd Embodiment of this invention performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 39P ... Port injection valve, 39C ... In-cylinder injection valve, 70 ... Electric control device, 71 ... CPU

Claims (4)

A port injection valve for injecting fuel in an intake passage upstream of the intake valve of the internal combustion engine;
An in-cylinder injection valve for directly injecting fuel in the combustion chamber of the internal combustion engine;
Applied to an internal combustion engine with
Based on the operating state of the internal combustion engine, the basic port injection amount, the basic port injection, and the port injection amount, which is the amount of fuel injected by the port injection valve, and the start and end of the opening period of the port injection valve Port injection determining means for determining at the beginning and at the end of basic port injection;
The in-cylinder injection amount, which is the amount of fuel injected by the in-cylinder injection valve, and the beginning and end of the valve opening period of the in-cylinder injection valve are determined based on the operating state of the internal combustion engine. In-cylinder injection determining means for determining the basic in-cylinder injection start period and the basic in-cylinder injection end period;
In a fuel injection control device for an internal combustion engine comprising:
The in-cylinder injection determining means includes
When it is determined that the basic in-cylinder injection end is on the more retarded side than the end of the intake valve opening period, the end of the in-cylinder injection valve opening period is set higher than the basic in-cylinder injection end period. Determined at an advanced timing, and the in-cylinder injection amount is determined to be a predetermined amount smaller than the basic in-cylinder injection amount,
The port injection determining means
When it is determined that the basic in-cylinder injection end is retarded from the end of the intake valve opening period, the port injection amount is determined to be an amount larger by the predetermined amount than the basic port injection amount. A fuel injection control device for an internal combustion engine configured to do so. The fuel injection control device for an internal combustion engine according to claim 1,
The in-cylinder injection determining means includes
When it is determined that the basic in-cylinder injection end time is retarded from the end of the intake valve opening period, the start time of the in-cylinder injection valve opening period is maintained at the basic in-cylinder injection start time. Determining the end of the in-cylinder injection valve opening period to be equal to the end of the intake valve opening period, and setting the in-cylinder injection amount to the basic in-cylinder injection end time rather than the basic in-cylinder injection amount. And an amount corresponding to the interval between the opening period of the intake valve and the end of the valve opening period,
The port injection determining means
When it is determined that the end of the basic in-cylinder injection is retarded from the end of the intake valve opening period, the port injection amount is larger than the basic port injection amount by an amount corresponding to the interval. A fuel injection control device for an internal combustion engine configured to determine a quantity. The fuel injection control device for an internal combustion engine according to claim 1 or 2,
The port injection determining means
When it is determined that the basic in-cylinder injection end is retarded from the end of the intake valve opening period, and the absolute value of the change rate of the port injection amount is greater than a predetermined change rate When determined, the port injection amount is determined so that the absolute value of the change speed matches the predetermined change speed;
The in-cylinder injection determining means includes
The basic in-cylinder injection end time is determined to be retarded from the end of the intake valve opening period, and the absolute value of the change rate of the port injection amount is greater than the predetermined change rate The in-cylinder injection amount is determined to be smaller than the basic in-cylinder injection amount by an amount obtained by subtracting the basic port injection amount from the determined port injection amount. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1 or 2,
The port injection determining means
It is determined that the basic in-cylinder injection end time is retarded from the end of the intake valve opening period, and the port injection amount reduction rate is determined to be greater than a predetermined reduction rate. And determining the port injection amount so that the decreasing speed matches the predetermined decreasing speed,
The in-cylinder injection determining means includes
When it is determined that the basic in-cylinder injection end is retarded from the end of the intake valve opening period, it is determined that the rate of decrease in the port injection amount is greater than the predetermined decrease rate. The in-cylinder injection amount is determined to be smaller than the basic in-cylinder injection amount by an amount obtained by subtracting the basic port injection amount from the determined port injection amount. Fuel injection control device.

Images