JP2014062493A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high combustion performance by suppressing deviation of an orientation direction of fuel spray by being affected by a gas flow velocity in an intake port.SOLUTION: An area ratio AR indicating a deviation degree of fuel spray to an intake valve is determined on the basis of a gas flow velocity (S101) and an injection pulse width (S102). In a case when conditions that the area ratio AR is lower than a set value SL, and the fuel spray is introduced into a combustion chamber through the intake valve while being deviated, a requested penetrating force is set to make the area ratio AR to become the set value SL or more (S103→S104). Here, when it is necessary to decrease the penetrating force to satisfy the requested penetrating force, the penetrating force of the fuel spray is decreased by split injection, lowering of fuel pressure, switching to a fuel injection valve of lower penetrating force, and the like (S105→S106). On the other hand, when it is necessary to increase the penetrating force of the fuel spray, the penetrating force of the fuel spray is increased by increasing the fuel pressure, switching to a fuel injection valve of higher penetrating force, and the like (S105→S107).

Description

  The present invention relates to a control device applied to an internal combustion engine that includes a fuel injection valve that injects fuel into an intake port during an intake stroke.

  In Patent Document 1, in an internal combustion engine provided with a rectifying plate that partitions the inside of an intake port, the shape of fuel spray injected from the fuel injection valve into the intake port has a shape that is long in the direction in which the inside of the intake pipe is partitioned by the rectifying plate. The fuel injection device is configured to improve the fuel vaporization performance in the intake port by setting the fuel spray to directly hit the umbrella portion of the intake valve and the inner wall of the intake port in the longitudinal direction. Is disclosed.

JP 2007-120491 A

  By the way, even if the spray characteristics of the fuel injection valve are set so that the fuel spray injected from the fuel injection valve directly hits a predetermined part such as the intake valve or the intake port, the intake port is not used in the fuel injection during the intake stroke. As the gas flow rate in the inside changes according to the engine operating conditions, the direction of fuel spray is deflected and the fuel spray is biased into the combustion chamber, which may reduce the combustibility.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for an internal combustion engine that can suppress variation in combustibility due to fuel spray being affected by a change in gas flow velocity in an intake port. And

  Therefore, in the present invention, the penetration force of the fuel spray is changed in a direction to suppress the deflection of the fuel spray injected from the fuel injection valve in the intake port with respect to the increase or decrease of the gas flow velocity in the intake port. did.

  According to the above invention, even if the gas flow velocity in the intake port changes with changes in the engine operating conditions, the deflection of the fuel spray in the intake port can be suppressed, so the fuel spray is introduced in a biased manner in the combustion chamber. This can be suppressed and high combustibility can be stably maintained.

1 is a system diagram showing an internal combustion engine in an embodiment of the present invention. It is a flowchart which shows the flow of penetration force control in embodiment of this invention. It is a figure which shows the correlation with the area ratio and the homogeneity of air-fuel | gaseous mixture in embodiment of this invention. It is a figure which shows the correlation with the injection pulse width and spraying speed in embodiment of this invention. It is a figure which shows the pattern of the injection pulse width in the division | segmentation injection in embodiment of this invention. It is a figure which shows the correlation of the fuel pressure and spraying speed in embodiment of this invention. 1 is a system diagram showing an internal combustion engine in an embodiment of the present invention.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of a vehicle internal combustion engine to which a control device according to the present invention is applied.
In FIG. 1, an internal combustion engine (engine) 1 includes a fuel injection valve 3 in an intake port (intake pipe) 2 upstream of the intake valve 4. The fuel injection valve 3 injects fuel into the intake port 2.

The fuel injected by the fuel injection valve 3 is sucked into the combustion chamber 5 together with air through the intake valve 4 to form an air-fuel mixture. The air-fuel mixture in the combustion chamber 5 is ignited and burned by spark ignition by the spark plug 6. The combustion gas in the combustion chamber 5 is discharged to the exhaust pipe 8 through the exhaust valve 7.
The electronic control throttle 10 is a means for adjusting the intake air amount of the internal combustion engine 1 by changing the opening degree by the throttle motor 9. The electronic control throttle 10 is provided upstream of the portion of the intake port 2 where the fuel injection valve 3 is disposed.

The fuel supply device 13 is a device that pumps the fuel in the fuel tank 11 to the fuel injection valve 3 by the fuel pump 12.
The fuel supply device 13 includes a fuel tank 11, a fuel pump 12, a pressure regulating valve (pressure regulator) 14, an orifice 15, a fuel gallery pipe 16, a fuel supply pipe 17, a fuel return pipe 18, a jet pump 19, and a fuel transfer pipe 20. I have.
The fuel pump 12 is an electric pump and is provided in the fuel tank 11.

The fuel supply pipe 17 is a pipe connecting the fuel pump 12 and the fuel gallery pipe 16, one end of the fuel supply pipe 17 is connected to the discharge port of the fuel pump 12, and the fuel gallery pipe is connected to the other end of the fuel supply pipe 17. 16 is connected.
Further, the fuel supply port of the fuel injection valve 3 is connected to the fuel gallery pipe 16, and fuel is distributed to each fuel injection valve 3 through the fuel gallery pipe 16.
The fuel return pipe 18 branches from the fuel supply pipe 17 in the fuel tank 11, and the end of the fuel return pipe 18 opens into the fuel tank 11.
The fuel return pipe 18 is provided with a pressure regulating valve 14, an orifice 15, and a jet pump 19 in order from the upstream side.

The pressure regulating valve 14 is generally configured by a valve body 14a that opens and closes the fuel return pipe 18 and an elastic member 14b such as a coil spring that presses the valve body 14a toward the valve seat upstream of the fuel return pipe 18. . The pressure regulating valve 14 opens when the fuel pressure supplied to the fuel injection valve 3 exceeds a set pressure (valve opening pressure) FPMIN, and closes when the fuel pressure is equal to or lower than the set pressure FPMIN. .
The pressure adjustment valve 14 is opened when the fuel pressure supplied to the fuel injection valve 3 becomes higher than the set pressure FPMIN. However, the orifice 15 provided on the downstream side of the pressure adjustment valve 14 passes through the fuel return pipe 18. The fuel flow rate returned to the fuel tank 11 is reduced. For this reason, the fuel pressure can be increased to a pressure exceeding the set pressure FPMIN by increasing the amount of fuel discharged from the fuel pump 12.
In addition, without providing the orifice 15, for example, the pressure regulating valve 14 can have a function of restricting the return flow rate.

The jet pump 19 transfers fuel through the fuel transfer pipe 20 by the flow of fuel returned into the fuel tank 11 through the pressure regulating valve 14 and the orifice 15.
The fuel tank 11 is a so-called vertical fuel tank in which a part of the bottom surface is raised and the bottom space is divided into two regions 11a and 11b. Since the suction port of the fuel pump 12 opens into the region 11a, the fuel in the region 11b remains unless the fuel in the region 11b is transferred to the region 11a side.

Therefore, the jet pump 19 applies a negative pressure to the fuel transfer pipe 20 by the flow of fuel returned into the region 11a of the fuel tank 11 via the pressure regulating valve 14 and the orifice 15, and the fuel transfer pipe 20 is opened. The fuel in the region 11b to be conducted is guided to the jet pump 19 through the fuel transfer pipe 20, and is discharged into the region 11a together with the return fuel.
In the present embodiment, the jet pump 19 is provided as described above. However, when the fuel tank 11 is not a so-called saddle type, that is, the bottom space of the fuel tank 11 is not separated, the fuel is supplied from the suction port of the fuel pump 12. When the fuel in the tank 11 can be sucked without remaining, the jet pump 19 and the fuel transfer pipe 20 can be omitted. Further, the fuel tank 11 is not a so-called saddle type, and the fuel supply device 13 can be provided without the fuel return pipe 18, the pressure adjustment valve 14, the orifice 15, the jet pump 19, and the fuel transfer pipe 20.

An ECM (engine control module) 31 having a microcomputer is a control device for controlling the internal combustion engine 1, and has a function of outputting an injection pulse signal for controlling a valve opening period of the fuel injection valve 3 and a spark plug 6. It has a function of controlling the ignition timing, the opening degree of the electronic control throttle 10, and the like.
An FPCM (fuel pump control module) 30 including a microcomputer outputs a drive signal for the fuel pump 12 to control the fuel pump 12.

The ECM 31 and the FPCM 30 can communicate with each other, and the ECM 31 transmits a signal PINS for instructing a drive duty ratio (operation amount) of the fuel pump 12 to the FPCM 30.
The drive duty ratio (%) of the fuel pump 12 is an operation amount for controlling the applied voltage of the motor that rotationally drives the fuel pump 12, and indicates the energization time ratio (on-time ratio) per cycle. Increases, the average applied voltage of the motor increases, and the discharge pressure (discharge flow rate) of the fuel pump 12 increases.
Further, the FPCM 30 transmits a signal DIAG or the like indicating the result of the self-diagnosis to the ECM 31.

  The ECM 31 is a fuel pressure sensor (pressure detecting means) 33 for detecting the fuel pressure FUPR in the fuel gallery pipe 16 that indicates the pressure of the fuel supplied to the fuel injection valve 3, and an accelerator pedal depression amount (accelerator opening) that is not shown. An accelerator opening sensor 34 for detecting ACC, an air flow sensor 35 for detecting the intake air flow rate QA of the internal combustion engine 1, a rotation sensor 36 for detecting the rotational speed NE of the internal combustion engine 1, a cooling water temperature TW (engine temperature of the internal combustion engine 1) ) Is detected, and an air-fuel ratio sensor 38 that detects the air-fuel ratio A / F of the internal combustion engine 1 according to the oxygen concentration of the exhaust gas is input.

The ECM 31 calculates the ignition timing (ignition advance value) based on engine operating conditions such as the load of the internal combustion engine 1 and the engine speed NE, and spark discharge by the spark plug 6 is performed at the ignition timing. Controls energization to an ignition coil (not shown).
The ECM 31 calculates the target opening of the electronic control throttle 10 from engine operating conditions such as the accelerator opening ACC, and controls the throttle motor 9 so that the actual opening of the electronic control throttle 10 approaches the target opening.

Further, the ECM 31 has a fuel pump so that the fuel pressure FUPR (actual fuel pressure) detected by the fuel pressure sensor 33 approaches the target fuel pressure TGFUPR determined based on the operating conditions (engine load, engine speed, etc.) of the internal combustion engine 1. A duty ratio DUTY in the duty control of 12 (motor) is determined, and a pulse signal PINS indicating the duty ratio DUTY (%) is transmitted to the FPCM 30 as a drive instruction signal for the fuel pump 12.
For example, the ECM 31 determines the duty ratio DUTY by calculating a proportional component, an integral component, and a differential component based on a deviation between the fuel pressure FUPR and the target fuel pressure TGFUPR.
The FPCM 30 sets a duty ratio DUTY (%) in the duty control of the motor of the fuel pump 12 based on the pulse signal PINS received from the ECM 31 side, and performs duty control of power supply to the motor of the fuel pump 12.

As described above, the ECM 31, the FPCM 30, the fuel pressure sensor 33, the electric fuel pump 12, and the like constitute a fuel pressure adjusting device (fuel pressure adjusting means) that variably adjusts the pressure (fuel pressure) of the fuel supplied to the fuel injection valve 3. To do.
It should be noted that the ECM 31 includes a circuit and a control function that the FPCM 30 includes, whereby a fuel pressure control system in which the ECM 31 and the FPCM 30 are integrated can be obtained.

Further, the ECM 31 calculates an injection pulse width TI (ms) for controlling the valve opening period (fuel injection amount) of the fuel injection valve 3 per cycle as follows.
The ECM 31 calculates a basic injection pulse width TP (ms) suitable for the case where the fuel pressure is a reference value based on engine operating conditions such as the intake air flow rate QA and the engine rotational speed NE, and this basic injection pulse width TP. Is corrected based on the fuel pressure FUPR, the output (air-fuel ratio) of the air-fuel ratio sensor 38, etc., and the final injection pulse width TI (ms) is calculated.

The ECM 31 outputs an injection pulse signal having an injection pulse width TI to the fuel injection valve 3 in the intake stroke of each cylinder, and controls the fuel injection amount and the injection timing by the fuel injection valve 3, so-called sequential injection control. I do.
The fuel injection valve 3 opens for a period corresponding to the injection pulse width TI, and injects an amount of fuel proportional to the valve opening time (ms).

The injection timing in the intake stroke injection by the fuel injection valve 3 is the timing at which the entire injection period is during the intake stroke (while the intake valve 4 is open), and the start of fuel injection is during the exhaust stroke (intake valve 4). However, it is possible to set the fuel injection timing mainly during the intake stroke (during the valve opening period of the intake valve 4).
That is, even when the start timing of fuel injection is before the opening of the intake valve 4, if the majority of the injection period overlaps with the opening period of the intake valve 4, it is included in the fuel injection during the intake stroke.
Further, fuel injection (intake stroke injection) in which the injection timing is during the intake stroke is performed under predetermined operating conditions. Under different operating conditions, for example, fuel is injected into an exhaust stroke in which the intake valve 4 is closed. Exhaust stroke injection can be performed.

Here, in the intake stroke injection, fuel is injected in a state where an intake air flow is generated in the intake port 2, and therefore, when the gas flow velocity (intake air flow velocity) in the intake port 2 changes due to a change in engine operating conditions, A deflection occurs in which the direction of fuel spray changes. When the fuel spray is deflected, the fuel is introduced into the combustion chamber in a biased manner, which may reduce the homogeneity of the air-fuel mixture and reduce the combustibility.
Therefore, the ECM 31 performs control to change the penetration force of the fuel spray in order to suppress the deflection of the fuel spray accompanying the change in the gas flow rate. FIG. 2 is a flowchart showing a flow of the penetrating force change control.
The penetration force of the fuel spray is expressed as, for example, a force obtained by multiplying the spray speed by the diameter of the fuel spray particles at the spray reach distance after a predetermined time has elapsed after the fuel injection from the fuel injection valve 3 (several milliseconds). The penetration force decreases as the spraying speed decreases or the particle diameter decreases, and conversely, as the spraying speed increases or the particle diameter increases, the penetration force increases. Here, since the diameter of the particles is basically determined by the diameter of the injection hole of the fuel injection valve 3, it is generally constant, and the penetration force changes according to the change of the spray speed.

The processing shown in the flowchart of FIG. 2 is executed at predetermined time intervals by the ECM 31. First, in step S101, based on the rotational speed NE of the internal combustion engine 1 and the torque (load) of the internal combustion engine 1, the current intake air The gas flow rate (intake flow rate) in port 2 is estimated.
Here, it is estimated that the gas flow rate becomes faster as the torque of the internal combustion engine 1 increases at the same engine speed NE, and the gas flow rate increases as the engine speed NE increases at the same torque. Is estimated to be faster. That is, it is estimated that the higher the engine speed NE and the higher the torque of the internal combustion engine 1, the faster the gas flow rate.

The torque of the internal combustion engine 1 is calculated by the ECM 31 based on intake pipe negative pressure (boost), intake air flow rate, throttle opening, accelerator opening, and the like.
Further, the estimation of the gas flow rate based on the engine operating state can be performed by searching from a map as shown in FIG. 2 or by calculation of a function having the engine operating state as a variable.
In addition, a sensor that outputs a signal corresponding to the gas flow rate is provided in the intake port 2, and the gas flow rate can be detected from the output of the sensor.
On the other hand, the engine speed NE is calculated by the ECM 31 based on the output of the rotation sensor (crank angle sensor) 36.

In step S102, the fuel spray is applied to the area of the opening where the intake valve 4 is lifted and opened from the gas flow rate obtained in step S101 and the spray penetration force (standard penetration force) at the injection pulse width TI. A ratio AR (%) of the passing area is calculated.
As an example, for each combination of the gas flow rate and the penetration force at the injection pulse width TI, the map storing the area ratio AR is referred to, interpolation processing is performed, and the gas flow rate and injection pulse width TI at that time are The area ratio AR corresponding to the penetrating power of is obtained.

The area ratio AR is a parameter indicating the degree of bias of the fuel spray with respect to the intake valve 4. When the area ratio AR is close to 100%, the fuel spray is applied over substantially the entire annular opening where the intake valve 4 is lifted and opened. The lower the numerical value of the area ratio AR, the greater the bias of the fuel spray, and the larger the area of the portion where the fuel spray does not pass.
As shown in FIG. 3, the higher the area ratio AR (the larger the area into which the fuel spray flows), the higher the homogeneity of the air-fuel mixture in the cylinder, and the higher the homogeneity, the higher the combustibility. As a result, exhaust properties and fuel efficiency can be improved.
In other words, when the area ratio AR is low (when the area where the fuel spray flows in is narrow), if the fuel injection is performed as it is, the exhaust property and the fuel consumption performance are deteriorated.

Further, the spray penetration force at the injection pulse width TI is a value calculated from the spray speed (m / s) and the particle size of the fuel spray when the injection pulse width TI is injected only once per cycle. (Penetration force = particle size × spraying speed).
As shown in FIG. 4, the ECM 31 calculates a higher spray speed as the injection pulse width TI becomes longer. On the other hand, the particle size of the spray is set to a fixed value or a smaller particle diameter as the injection pulse width TI becomes longer. Based on these spray speeds and particle sizes, the penetration force of the spray with the injection pulse width TI is set.

The penetration force of the spray with the injection pulse width TI is the target fuel pressure TGFUPR in which the pressure of the fuel supplied to the fuel injection valve 3 is determined based on the operating conditions (load, rotational speed, etc.) of the internal combustion engine 1. It is calculated on the assumption.
Here, the direction in which the fuel spray is changed from the state in which the fuel spray injected from the fuel injection valve 3 is sucked into the combustion chamber over substantially the entire annular opening where the intake valve 4 lifts and opens. If the fuel spray flows toward the side closer to the spark plug 6 and conversely the fuel spray flows toward the side closer to the cylinder bore, the area ratio AR decreases.

In the present embodiment, when the gas flow rate is medium and the spray penetration force at the injection pulse width TI is medium, the spray characteristic (of the fuel injection valve 3) is set so that the area ratio AR is the highest. The direction of the nozzle hole, spray angle, spray particle size, spray speed, etc.) are set.
For this reason, if the gas flow rate becomes faster than the gas flow rate at which the area ratio AR is the highest, the direction of fuel spray is deflected due to the influence of the fast gas flow rate, and the area ratio AR decreases. On the contrary, if the flow velocity is slow, the influence of the gas flow velocity on the direction of fuel spray is reduced, so that the fuel spray is also deflected and the area ratio AR is reduced.

Similarly, if the penetration force of the spray with the injection pulse width TI becomes weaker than that in the case where the area ratio AR is the highest, the degree to which the direction of fuel spray is influenced by the gas flow rate is relatively increased. If the spray is deflected and the area ratio AR decreases, and if the penetration force is increased, the influence of the gas flow rate on the spray direction is suppressed, so that the fuel spray is deflected and the area ratio AR will decrease.
Therefore, the area ratio AR obtained in step S102 becomes smaller as the spray penetration force at the injection pulse width TI is weaker and the gas flow rate is faster, and the gas flow rate is slower and at the injection pulse width TI. The smaller the spray penetration force, the smaller the area ratio AR, and the smaller the area ratio AR, the greater the direction of fuel spray change from the optimum direction.

In step S102, the area ratio AR corresponding to the penetration force and the gas flow rate at the injection pulse width TI at that time is obtained based on the characteristics of the area ratio AR based on the combination of the fuel spray penetration force and the gas flow rate.
In the next step S103, it is determined whether or not the area ratio AR obtained in step S102 is equal to or greater than a set value SL (for example, 75%).

The set value SL of the area ratio AR is the minimum value of the area ratio AR that can obtain the target fuel efficiency and exhaust properties. Therefore, when the area ratio AR is lower than the set value SL, it can be determined that the fuel efficiency and the exhaust properties are lower than the target due to the decrease in the homogeneity of the air-fuel mixture in the cylinder. On the other hand, if the area ratio AR is equal to or greater than the set value SL, the fuel spray directing direction is substantially appropriate and the homogeneity of the air-fuel mixture in the combustion chamber is sufficient even without performing the process of changing the penetration force. It can be judged that it is very expensive.
Therefore, if it is determined in step S103 that the area ratio AR obtained in step S102 is greater than or equal to the set value SL, the process proceeds to step S108.

In step S108, the standard injection control, that is, the injection with the injection pulse width TI per cycle is performed once, and the fuel pressure is controlled to the above-described target fuel pressure TGFUPR (standard fuel pressure). The process for changing is not performed.
That is, when the area ratio AR is equal to or greater than the set value SL, a sufficient degree of homogeneity can be obtained without changing the penetration force of the fuel spray. Therefore, standard control (single injection with an injection pulse width TI per cycle, fuel pressure control based on the target fuel pressure TGFUPR) is performed without changing the injection control and the fuel pressure control.

On the other hand, when the area ratio AR is lower than the set value SL, if the fuel injection is performed without changing the penetration force, the fuel efficiency and the exhaust property are more than the target due to the decrease in the homogeneity of the air-fuel mixture in the cylinder. There is a possibility of lowering.
Therefore, the process proceeds to step S104 and subsequent steps, and a process of changing the penetration force of the fuel spray is performed so that the area ratio AR becomes equal to or larger than the set value SL. In other words, since the area ratio AR is less than the set value SL due to the deflection of the fuel spray, the penetration force is changed in a direction to suppress the deflection of the fuel spray and the area ratio AR is equal to or greater than the set value SL. To be close to.

In step S104, the required penetration force for setting the area ratio AR to be equal to or greater than the set value SL is calculated based on the gas flow rate at that time.
Here, when the area ratio AR falls below the set value SL due to an increase in the gas flow rate from the standard state, a penetration force larger than the penetration force at the injection pulse width TI is calculated as a required value. In addition, when the area ratio AR falls below the set value SL due to a decrease in the gas flow rate from the standard state, a penetration force smaller than the penetration force at the injection pulse width TI is calculated as the required value.

In step S105, the required penetrating force obtained in step S104 and the standard penetrating force obtained when the area ratio AR is obtained in step S102 (the penetrating force when one injection is performed with the injection pulse width TI per cycle). In order to obtain the required penetrating force, it is determined whether the penetrating force is increased or decreased.
If the penetration force at the injection pulse width TI is higher than the required penetration force, and the area ratio AR (homogeneity) can be increased by reducing the penetration force, the process proceeds to step S106.

In step S106, a setting is made to weaken the penetration force of the fuel spray injected from the fuel injection valve 3 from the standard.
The standard penetrating force means that the fuel pressure is controlled to the target fuel pressure TGFUPR, and the fuel injection valve 3 used for fuel injection in step S108 performs one injection with an injection pulse width TI per cycle. It is the penetration power of.
As a process for weakening the penetration force of the fuel spray from the standard, the setting for performing the injection with the injection pulse width TI once can be changed to the divided injection for performing the injection with the injection pulse width TI divided into a plurality of times.

As shown in FIG. 4, when the injection pulse width is shortened, the spray flow rate is slowed down and the penetration force is weakened. Therefore, if the injection pulse width per injection is shortened by divided injection, the same amount of fuel as the total amount can be obtained. While spraying, the penetration force of the fuel spray can be weakened to approach the required penetration force. When the fuel spray penetration force approaches the required penetration force, the area ratio AR increases, the homogeneity of the air-fuel mixture increases, and the fuel efficiency and exhaust properties are improved.
When the penetrating force at the injection pulse width TI is higher than the required penetrating force, the penetrating force is excessive with respect to the gas flow velocity, so that the deflection caused by the gas flow in the intake port 2 becomes too small. If the penetration force is weakened, the deflection of the fuel spray relatively affected by the gas flow becomes larger, and the direction of the fuel spray can be deflected in the direction in which the homogeneity of the mixture becomes higher. Become.

In the divided injection, the injection pulse width at which the required penetration force is obtained at the current gas flow rate is determined based on the gas flow velocity at that time, and the injection pulse width TIPN at which the required penetration force is obtained is divided by the injection pulse width TI. Let N be the integer value obtained by rounding down the fractional part of the quotient.
Here, N indicates the number of injections with the injection pulse width TIPN.
For simplicity, the injection pulse width TIPN can be stored in advance as a fixed value.

Then, as shown in FIG. 5B, the difference between the sum pulse obtained by performing the injection with the injection pulse width TIPN only N times and the injection pulse width TI (difference = TI−TIPN × N) is the fuel injection valve. If it is less than the minimum injection pulse width TIMIN 3 (0 ≦ difference <TIMIN), the injection with the injection pulse width TIPN is performed N times during the same intake stroke.
The minimum injection pulse width TIMIN is the minimum injection pulse width at which the fuel injection valve 3 can obtain an injection amount proportional to the injection pulse width. When injection is performed with an injection pulse width less than the minimum injection pulse width TIMIN, The injection amount becomes indefinite.

Therefore, split injection is performed in which injection with an injection pulse width TIPN is performed N times during the same intake stroke without performing injection with an injection pulse width less than the minimum injection pulse width TIMIN. At this time, the total injection pulse width of the divided injection is insufficient with respect to the injection pulse width TI for a time shorter than the minimum injection pulse width TIMIN, but the deviation of the air-fuel ratio can be suppressed within an allowable range.
On the other hand, as shown in FIG. 5A, the difference (difference = TI−TIPN × N) between the total pulse obtained by performing the injection with the injection pulse width TIPN only N times and the injection pulse width TI is the fuel injection valve. 3 is equal to or greater than the minimum injection pulse width TIMIN (TIMIN ≦ difference <TIPN), the sum of N injections with the injection pulse width TIPN and one injection with the difference (difference = TI−TIPN × N) is “N + 1” The divided injection is performed so that the number of injections is performed during the same intake stroke.

Here, in the injection with the pulse width corresponding to the difference, a fuel spray having a penetration force weaker than the required penetration force is injected, but the air-fuel mixture is mainly injected N times with the injection pulse width TIPN. Since it is formed, the homogeneity of the air-fuel mixture can be sufficiently increased.
As described above, the fuel spray is switched from the injection in which the injection with the injection pulse width TI is performed only once during the intake stroke to the divided injection in which the injection pulse width TI is divided into a plurality of times during the intake stroke. The penetration force is reduced, the penetration force is excessive with respect to the gas flow rate, the spray directing direction is deviated from the optimum direction, and the area ratio AR (homogeneity) is suppressed from decreasing.
In other words, by reducing the penetration force of the fuel spray according to the decrease in the gas flow rate, the directing direction of the fuel spray changes with the decrease in the gas flow rate, and the area ratio AR (homogeneity) is suppressed from decreasing. To do.

In addition to the process of shortening the injection time per time by split injection as described above, the fuel spray is also reduced by lowering the fuel supply pressure (fuel pressure) to the fuel injection valve 3 below the standard fuel pressure (target fuel pressure TGFUPR). You can weaken the penetrating power.
That is, as shown in FIG. 6, the higher the fuel pressure, the faster the fuel spray speed, and the faster the fuel spray speed, the higher the penetration force. By reducing the fuel pressure, the fuel spray penetration is increased. The power can be reduced.

When the penetration pressure is weakened by lowering the fuel pressure, a fuel pressure (<standard fuel pressure) that obtains the required penetration force with respect to the conditions of the gas flow velocity and the injection pulse width TI is obtained, and the fuel pump 12 The drive duty ratio of the (motor) is controlled.
For simplicity, set the fuel pressure to obtain the required penetration force based on either the gas flow velocity or the injection pulse width TI and the required penetration force, or fix the fuel pressure to weaken the penetration force. It can be stored in advance as a value.

Further, the fuel pressure can be decreased and the divided injection can be simultaneously performed to reduce the penetration force of the fuel spray, or the fuel pressure can be decreased and the divided injection can be switched depending on the conditions.
For example, when the injection pulse width TI is long and the penetration force is to be reduced to the required value only by the divided injection, the fuel pressure is increased when the number of divisions increases and the divided injection cannot be terminated during the intake stroke. By reducing the number, it is possible to reduce the number of divisions (increase the injection pulse width per one time) and end the divided injection during the intake stroke.

In split injection, the interval time from the end of injection to the start of injection needs to be a certain time or more, and the time from the first start of split injection to the end of the final injection is the injection pulse width by the interval time. If it becomes longer than TI and the number of divisions increases, it may become impossible to inject all the fuel during the intake stroke.
Here, if the fuel pressure is lowered, the injection pulse width that provides the required penetration force becomes longer and the number of divisions decreases, and by reducing the number of divisions, the injection period is shortened and all the fuel is removed during the intake stroke. It becomes possible to make it spray.

  Also, as shown in FIG. 7, two fuel injection valves 3a and 3b having different penetration forces at the same injection pulse width are provided in each cylinder. For example, when the process proceeds to step S108, two fuel injection valves 3a and 3b are provided. When fuel injection is performed by the fuel injection valve 3a having the higher penetration force among the injection valves 3a and 3b and the process proceeds to step S106, fuel injection is performed by the fuel injection valve 3b having the weaker penetration force. Can be performed.

The two fuel injection valves 3a, 3b having different penetrating forces are fuel injection valves having different fuel spray particle sizes and / or different fuel spray flow rates.
In addition, the penetration force may be reduced by performing a combination of switching to the fuel injection valve 3 that injects fuel spray having a weaker penetration force as described above and at least one of divided injection and fuel pressure reduction. it can.

On the other hand, if it is determined in step S105 that the penetration force at the injection pulse width TI is lower than the required penetration force and the penetration ratio can be increased, the area ratio AR (homogeneity) can be increased. Proceed to
In step S107, processing for increasing the penetration force of fuel spray from the standard is performed.

As a process of increasing the penetration force of fuel spray, a process of increasing the fuel supply pressure (fuel pressure) to the fuel injection valve 3 can be performed.
As shown in FIG. 6, the higher the fuel pressure, the faster the fuel spray speed, and the faster the fuel spray speed, the higher the penetration force. By increasing the fuel pressure, the fuel spray penetration power is increased. Can strengthen.

Further, as a process for increasing the penetration force of the fuel spray, a fuel injection valve 3 having a stronger penetration force of the fuel spray is provided in each cylinder separately from the fuel injection valve 3 used in the fuel injection in step S108. In step S107, the fuel injection valve 3 having the stronger penetration force of the fuel spray of the two fuel injection valves 3 can be used.
In addition to the fuel injection valve used in step S108, a fuel injection valve having a stronger or weaker penetration force is provided, and adjustment of the penetration force by switching the fuel injection valve is performed in one of steps S106 and S107. Can be done. Further, three fuel injection valves having three penetration forces of large, medium, and small are provided in each cylinder. A fuel injection valve having a medium penetration force is used in step S108, and a fuel injection valve having the strongest penetration force in step S107. In step S106, it is possible to use the fuel injection valve having the weakest penetration force.

  Moreover, while executing the control to reduce the penetration force and approach the required penetration force (step S106), the control to increase the penetration force and approximate the required penetration force (step S107) can be omitted. Conversely, the control for increasing the penetration force to approach the required penetration force (step S107), while the control for reducing the penetration force to approach the required penetration force (step S106) can be omitted.

In the above embodiment, the area ratio AR is set as a state quantity for determining the deflection of the fuel spray, and it is determined whether or not the penetration force needs to be changed based on the area ratio AR. Without setting, it is possible to change the penetration force. For example, in step S102, it is possible to determine the injection pulse width and the fuel pressure per one time in the divided injection from the gas flow velocity and the spray penetration force at the injection pulse width TI.
Further, as a means for changing the penetration force of the fuel spray, a known means can be selected as appropriate, and the technical idea of changing the penetration force in a direction to suppress the deflection of the fuel spray accompanying the change of the gas flow rate. It can be implemented in various different embodiments within the scope.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) The control device for an internal combustion engine according to claim 1, wherein the penetration force of the fuel spray is changed by changing at least one of the particle size and the flow velocity of the fuel spray.
According to the above invention, the penetrating force changes according to the particle size and flow velocity of the fuel spray, so that at least one of the particle size and the flow velocity is changed to suppress the deflection of the fuel spray in the intake port. Change penetrating power.
Here, the penetration force increases as the flow rate of the fuel spray increases, and the penetration force increases as the particle size of the fuel spray increases. For example, it is necessary to increase the penetration force to suppress the deflection of the fuel spray. In some cases, the fuel spray flow rate is increased and / or the fuel spray particle size is increased.

(B) When the penetration force is weakened in order to suppress the deflection of the fuel spray, the fuel amount per cycle is divided into a plurality of times from the batch injection that injects the fuel amount per cycle once. The control apparatus for an internal combustion engine according to claim 3, wherein the control is switched to injection.
According to the above invention, when the penetrating force becomes excessive with the change in the gas flow rate and the fuel spray directing direction is deflected, the fuel amount per cycle is divided into multiple injections from the batch injection. By switching to injection, the flow rate of fuel spray is slowed and the penetration force of fuel spray is reduced.

(C) The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the gas flow velocity in the intake port is estimated based on a rotational speed of the internal combustion engine and a load of the internal combustion engine.
According to the above invention, the gas flow velocity in the intake port is estimated based on the engine rotation speed and the engine load, and the penetration force is changed so as to suppress the deflection of the fuel spray due to the increase or decrease in the estimated gas flow velocity.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine (engine), 3 ... Fuel injection valve, 11 ... Fuel tank, 12 ... Fuel pump, 14 ... Pressure regulating valve (pressure regulator), 15 ... Fuel gallery piping, 16 ... Fuel supply piping, 17 ... Fuel return Piping, 30 ... FPCM (Fuel pump control module), 31 ... ECM (Engine control module), 33 ... Fuel pressure sensor (pressure detection means)

Claims (3)

In a control device applied to an internal combustion engine having a fuel injection valve that injects fuel into an intake port in an intake stroke,
An internal combustion engine that changes a penetration force of the fuel spray in a direction that suppresses a deflection of the fuel spray injected from the fuel injection valve in the intake port with respect to an increase or decrease in a gas flow velocity in the intake port. Control device.   The penetration force of the fuel spray is decreased with respect to the decrease in the gas flow velocity in the intake port, and the penetration force of the fuel spray is increased with respect to the increase in the valve opening time per cycle of the fuel injection valve. The control device for an internal combustion engine according to claim 1, wherein the control device is decreased.   The penetration force of the fuel spray by at least one of a change in the number of divisions of fuel injection by the fuel injection valve, a change in the pressure of fuel supplied to the fuel injection valve, and a switching of the fuel injection valve for injecting fuel The control device for an internal combustion engine according to claim 1 or 2, wherein