JP2005069045A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine executing appropriate control of air fuel ratio during a transition period by accurately estimating suction air pressure in an intake manifold at a completion of a suction stroke. <P>SOLUTION: Additional injection permission crank angle θ is established based on direct enter rate of fuel in a suction stroke. Suction air pressure (point E) or suction air quantity at completion of suction stroke is estimated by using change quantity (point C, point D) of suction air pressure or suction air quantity in the intake manifold (I/M) estimated every predetermined period (5ms) in neighborhood of the additional injection permission crank angle θ. As embodiment, fuel of additional fuel injection quantity (II) calculated based on the estimated suction air pressure (point E) or suction air quantity during transition of operation condition is additionally injected during suction stroke to control air fuel ratio at a predetermined air fuel ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and is useful for, for example, appropriate control of an air-fuel ratio during a transition in an intake pipe injection type internal combustion engine.

  Generally, in an intake pipe injection type internal combustion engine (for example, a gasoline engine), the intake air amount is measured before the intake stroke, and fuel is supplied on the assumption that the intake air amount does not change. There is a difference between the intake air amount and the actual intake air amount, and this difference appears as an A / F (air-fuel ratio) error of acceleration lean and deceleration rich.

  As countermeasures, various methods have been devised for predicting the in-cylinder intake amount at the end of the intake stroke when the injection amount is calculated. However, when the fuel is injected before the intake stroke and then suddenly accelerated and the intake air amount in the cylinder increases, it is necessary to inject fuel again to achieve an appropriate air-fuel ratio. As a method for giving the timing of the injection amount and the drive time (injection pulse width), asynchronous injection that gives the drive pulse width of the fuel injection valve by multiplying the amount of change in the throttle opening calculated every predetermined time by a coefficient has been conventionally performed. (See Patent Document 1).

Japanese Patent Laid-Open No. 7-233749 (page 4-10, FIG. 1-11)

  However, the relationship between the rate of change of the throttle opening and the amount of additional injected fuel that should actually be corrected is greatly affected by the relationship between the throttle opening and its effective area, the pressure in the intake pipe, and atmospheric pressure. It cannot be approximated.

  In addition, during the intake stroke, the ratio of fuel transported into the cylinder (direct injection rate) changes abruptly depending on the injection timing, so the required injection amount is completely different even at the same rate of change in the throttle opening. This is also the reason why the prediction approximation is not successful. In other words, even if asynchronous injection is performed, air-fuel ratio control as intended cannot be performed unless the timing of additional injection and the amount of injected fuel are controlled in consideration of the direct injection rate.

  The present invention has been made in view of the above problems, and provides a fuel injection control device for an internal combustion engine that accurately predicts the intake air pressure of the intake manifold at the end of the intake stroke and performs appropriate control of the air-fuel ratio at the time of transition. The purpose is to do.

A fuel injection control device for an internal combustion engine according to the present invention that solves the above-mentioned problems is detected by a throttle opening degree detecting means for detecting an opening degree of a throttle disposed in an intake passage of the internal combustion engine, and the throttle opening degree detecting means. Effective opening area calculating means for calculating the effective opening area of the throttle according to the throttle opening.
The main injection fuel amount may be calculated using any of the conventional methods. The main injection fuel amount is set according to the operating state, and the main injection fuel amount is being sucked in synchronization with a predetermined crank angle. To supply.
Then, the pressure ratio detecting means for detecting or estimating the pressure ratio before and after the throttle, the pressure ratio detected or estimated by the pressure ratio detecting means, and the effective opening area by the effective opening area calculating means, Prediction means for predicting the intake pressure or in-cylinder intake amount in the intake passage on the downstream side every predetermined time, and additional injection permission for setting a crank angle for permitting additional injection based on the direct fuel injection rate during the intake stroke Crank angle setting means, and the predicting means predicts an intake pressure or in-cylinder intake amount at the end of the intake stroke based on a change in intake pressure or in-cylinder intake amount predicted in the vicinity of the additional injection permission crank angle. The fuel injection control means outputs the additional injection fuel amount calculated based on the predicted intake pressure or in-cylinder intake amount to the additional injection permission class during the intake stroke. By additional injection after click angle, to control the air-fuel ratio of the internal combustion engine to a predetermined air-fuel ratio.

  In the fuel injection control device for an internal combustion engine according to the present invention for solving the above-mentioned problems, the pressure ratio detection means includes an intake passage pressure detection means for detecting an intake pressure in the intake passage downstream of the throttle, and a prediction means includes The intake pressure at the end of the intake stroke is predicted using the average pressure during one stroke of the intake pressure by the intake passage pressure detecting means and the amount of change in the intake pressure predicted before the start of the intake stroke, The injection control means sets the main injection fuel amount based on the predicted intake pressure.

  Further, in the fuel injection control device for an internal combustion engine according to the present invention that solves the above-described problem, when the rotational speed of the internal combustion engine is equal to or higher than a predetermined rotational speed, the prediction means The intake pressure at the end of the intake stroke is predicted using the average pressure during one stroke and the amount of change in the intake pressure predicted before the start of the intake stroke, and the fuel injection control means Control of the fuel amount calculated based on the intake stroke before and after the start of the intake stroke, and the prediction of the intake pressure after predicting the intake pressure at the end of the intake stroke before the start of the intake stroke by the predicting means, Alternatively, the additional injection after the additional injection after the start of the intake stroke by the fuel injection control means is prohibited.

  In the fuel injection control device for an internal combustion engine according to the present invention for solving the above-described problem, the pressure ratio detection means includes an intake air amount detection means for detecting an intake air amount flowing through the intake passage, and the prediction means includes the intake air amount. The in-cylinder intake amount at the end of the intake stroke is predicted using the average intake amount during one stroke of the intake amount by the detection means and the change amount of the in-cylinder intake amount predicted before the start of the intake stroke, and the fuel The injection control means sets the main injection fuel amount based on the predicted in-cylinder intake amount.

  The fuel injection control device for an internal combustion engine according to the present invention that solves the above-described problems is characterized in that the fuel injection control means includes a main injection fuel amount and a direct injection rate thereof, an additional injection fuel amount and a direct injection rate thereof, and a wall surface of the intake passage. A fuel adhesion amount calculating means for calculating an adhesion amount of fuel adhering to the fuel, and the fuel injection control means evaporates and transports the current main injection fuel amount from the previous fuel adhesion amount by the fuel adhesion amount calculation means. Correct the amount to be reduced.

  In the fuel injection control apparatus for an internal combustion engine according to the present invention for solving the above-mentioned problems, the pressure ratio detection means includes an intake passage pressure detection means for detecting an intake pressure in the intake passage downstream of the throttle, and the prediction means Is the first intake pressure at the end of the intake stroke, using the average pressure during one stroke of the intake pressure detected by the intake passage pressure detecting means and the predicted change in intake pressure before the start of the intake stroke. The fuel injection control means controls to additionally inject the first fuel amount calculated based on the predicted first intake pressure after the start of the intake stroke, and the prediction means The second intake pressure at the end of the intake stroke is predicted based on the change amount of the intake pressure predicted in the vicinity of the additional injection permission crank angle, and the fuel injection control means is calculated based on the predicted second intake pressure. Second burn Amounts, by controlling so as to add injected into the additional injection enabling crank angle later in the intake stroke, to control the air-fuel ratio of the internal combustion engine to a predetermined air-fuel ratio.

  The fuel injection control device for an internal combustion engine according to the present invention that solves the above-mentioned problems is that the second intake pressure is predicted by the intake pressure prediction means when the rotational speed of the internal combustion engine is equal to or higher than a predetermined rotational speed, or An additional injection of the second fuel amount by the fuel injection control means is prohibited.

  In the fuel injection control device for an internal combustion engine according to the present invention for solving the above-mentioned problems, the fuel injection control means includes a main injection fuel amount, its direct injection rate, a first fuel amount, its direct injection rate, a second fuel amount, and its direct input. And a fuel adhesion amount calculating means for calculating an adhesion amount of fuel adhering to the wall surface of the intake passage according to a ratio, and the fuel injection control means determines the current main injection fuel amount as a previous time by the fuel adhesion amount calculation means. The amount of evaporation transported from the fuel adhering amount is corrected to decrease.

  In the fuel injection control device for an internal combustion engine according to the present invention that solves the above-described problem, the pressure ratio detection unit includes an intake amount detection unit that detects an intake amount flowing through the intake passage, and the prediction unit includes the intake air The first intake amount at the end of the intake stroke using the average intake amount during one stroke of the in-cylinder intake amount detected by the amount detection means and the predicted change amount of the in-cylinder intake amount before the start of the intake stroke The fuel injection control means performs control so that the first fuel amount calculated based on the predicted first intake air amount is additionally injected after the start of the intake stroke, and the predicting means further includes: The second intake air amount at the end of the intake stroke is predicted based on the change amount of the in-cylinder intake air amount estimated in the vicinity of the additional injection permission crank angle, and the fuel injection control means calculates based on the predicted second intake air amount. The second amount of fuel that has been By controlling so as to add injected injection enabling crank angle later, to control the air-fuel ratio of the internal combustion engine to a predetermined air-fuel ratio.

  According to the first to fifth aspects of the present invention, after the main fuel injection, the intake pressure at the end of the intake stroke or the intake air amount into the cylinder is appropriately predicted, and the vicinity of the additional injection permission crank angle during the intake stroke. In addition, a fuel amount corresponding to the intake pressure or the intake air amount can be additionally injected into the cylinder, and the air-fuel ratio can be controlled to a target air-fuel ratio corresponding to the operating state. Furthermore, the amount of attached liquid film is calculated according to a plurality of injection pulse widths and injection timings for one cylinder, and the evaporation transport amount in the next intake stroke in the same cylinder is corrected. , Exhaust gas, fuel consumption, drivability can be improved.

According to the sixth to eighth aspects of the present invention, after the main fuel injection, the intake pressure at the start of the intake stroke and at the end of the intake stroke in the vicinity of the additional injection permission crank angle is appropriately predicted, and before and after the intake stroke and A fuel amount corresponding to the intake pressure can be additionally injected into the cylinder in the vicinity of the additional injection permission crank angle during the intake stroke, and the air-fuel ratio can be accurately controlled by the target air-fuel ratio according to the operating state. .
Further, the amount of the attached liquid film is calculated according to a plurality of injection pulse widths and injection timings by main fuel injection, first additional injection, and second additional injection for one cylinder, and at the next intake stroke in the same cylinder Therefore, the air-fuel ratio error can be eliminated and exhaust gas, fuel consumption, and drivability can be improved.

  According to the ninth aspect of the present invention, as in the sixth aspect of the present invention, after the main fuel injection, before the start of the intake stroke and at the end of the intake stroke in the vicinity of the additional injection permission crank angle, Each intake air amount is properly predicted, and the fuel amount corresponding to the intake air amount can be additionally injected into the cylinder before and after the intake stroke and in the vicinity of the additional injection permission crank angle during the intake stroke, and the air-fuel ratio is operated. It can be accurately controlled by the target air-fuel ratio according to the state.

FIG. 1 is a configuration diagram showing an example of an embodiment of an internal combustion engine and a fuel injection control device thereof according to the present invention.
Here, a four-cylinder four-cycle gasoline engine will be described as an example of an internal combustion engine, but the present invention can be applied to other multi-cylinder engines.

  As shown in FIG. 1, an engine 1 which is an internal combustion engine has an intake pipe injection type fuel injection control device. The intake system of the engine 1 includes an air cleaner 2, an intake passage 3, a surge tank 4, and an intake manifold 5 (hereinafter abbreviated as I / M) from the upstream side. The intake air that has been purified by the air cleaner 2 and introduced into the intake passage 3 is adjusted in flow rate by a throttle valve 6 provided in the intake passage 3, and then distributed to each cylinder by an I / M 5 through a surge tank 4. Is done. The intake air is mixed with the fuel injected from the fuel injection valve 7 into each intake port 8 and introduced into each cylinder.

  The exhaust system of the engine 1 includes an exhaust passage 9, an unillustrated catalyst, a silencer, and the like from the upstream side. The fuel introduced into each cylinder is ignited by the spark plug 10 and burned. The exhaust gas generated by the combustion passes through the exhaust passage 9 from the exhaust port 11 and is exhausted through the catalyst and the silencer.

  The engine 1, the fuel injection valve 7 and the like are controlled and operated by an electronic control unit 21 (hereinafter abbreviated as ECU). The ECU 21 includes a control program, a control map, a storage device (ROM, RAM, etc.) used for calculation, a central processing unit (CPU) that performs calculation processing, a timer counter, an interface that handles input and output of control signals, and the like.

  As input signals to the ECU 21, an accelerator opening sensor 22 that detects the amount of operation of the accelerator pedal, an atmospheric pressure sensor 23 (atmospheric pressure detecting means) that detects atmospheric pressure, and a throttle valve opening that detects the opening of the throttle valve 6. Degree sensor 24 (throttle opening detection means), I / M pressure sensor 25 (intake passage pressure detection means) for detecting the intake pressure of I / M 5 that is the intake passage downstream of throttle valve 6, and the rotation angle of the crankshaft of the engine There is a signal from a crank angle sensor 26 (which also serves as a rotational speed sensor of the engine 1), a water temperature sensor 27 which detects the coolant temperature of the engine 1, and the like.

  The output signal from the ECU 21 includes a fuel injection valve 7 that injects an appropriate amount of fuel according to the operating state, a spark plug 10 that ignites the fuel in the cylinder, and a step motor that controls the opening of the throttle valve 6. There is a control signal to 28 etc.

  For example, the ECU 21 controls the ignition timing of the spark plug 10 based on the engine rotational speed Ne obtained from the signal value of the crank angle sensor 26, the I / M pressure signal from the I / M pressure sensor 25, and the like. Based on the target throttle opening obtained from the accelerator operation amount from the opening sensor 22, the vehicle speed, and the like, and the actual throttle opening signal TPS from the throttle valve opening sensor 24, the opening of the throttle valve 6 is adjusted by the step motor 28. Control. Further, the ECU 21 controls the injection amount of the fuel injection valve 7 based on the fuel injection amount calculated from the I / M pressure sensor 25.

  The fuel injection control device for an internal combustion engine according to the present invention basically has the above-described configuration, and an appropriate air-fuel ratio can be obtained by performing the fuel injection control method according to the present invention. Therefore, the fuel injection control method according to the present invention will be described in detail below.

The fuel injection control method according to the present invention is characterized in that the additional injection permission crank angle is defined as an index of the timing for performing the additional injection. The purpose of defining the additional injection permission crank angle is an index for performing additional injection at the crank angle as slow as possible so as to cope with the intake pressure change during the transition as much as possible. Specifically, as will be described with reference to FIG. 2, the direct injection rate changes depending on the crank angle, and by understanding this characteristic, additional injection at a slower crank angle, in other words, more accurate intake pressure Additional injection based on the change can be performed, and as a result, more appropriate air-fuel ratio control becomes possible.
Here, the direct injection rate is the first intake stroke after fuel injection (including during fuel injection) of the fuel injected from the fuel injection valve 7 into the intake port 8 and is introduced directly into the cylinder or in a vaporized state. It is the ratio of the burned fuel.

  FIG. 2 is a diagram for explaining the direct injection rate during the intake stroke, the additional injection permission crank angle derived from the direct injection rate, and the correction coefficient.

As shown in FIG. 2 (a), the direct injection rate has a characteristic that the crank angle at which fuel injection starts is constant up to a predetermined crank angle, then drops and finally becomes zero. In addition, the direct injection rate varies depending on the temperature of the cooling water for cooling the engine, that is, the temperature of the intake pipe and the rotational speed of the engine. The lower the temperature, the lower the direct entry ratio (the more fuel adheres to the intake pipe wall) The higher the rotation speed, the faster the crank angle becomes zero.
In the present invention, attention is paid to the intake flow velocity into the cylinder during the intake stroke with respect to the crank angle, and it is considered that the direct entry rate decreases at a slow crank angle.

  In other words, since the direct injection rate sharply decreases at a crank angle slower than a predetermined crank angle, if additional injection is performed at an extremely slow crank angle, fuel cannot be supplied into the cylinder. However, in order to be able to follow the latest intake pressure change, it is desirable that the additional injection be performed at the latest possible crank angle (crank angle close to the end of the intake stroke). Therefore, as shown in FIG. 2B, the injection limit crank angle can be first defined by considering the limit value of the direct entry rate. Further, the maximum pulse width necessary for introducing a predetermined amount of fuel into the cylinder is derived from the direct injection ratio with respect to the crank angle. Therefore, by considering the injection limit crank angle and the necessary maximum pulse width with respect to the crank angle, the additional injection permission crank angle can be defined. Based on the injection limit crank angle, an angle earlier than the crank angle by a predetermined angle (or a predetermined time) is set. The additional injection permission crank angle is set (additional injection permission crank angle setting means).

  The above-mentioned injection limit crank angle defines an angle at which the fuel hardly enters the cylinder when the crank angle is slower than this, and the direct injection rate is somewhat lowered as the additional injection permission crank angle, but a certain amount of fuel Is an angle that can be transported (for example, a direct entry rate of about 50% to 70%). Further, the predetermined angle (predetermined time) varies depending on operating conditions (for example, engine speed, cooling water temperature, etc.), and specifically, for example, 5 ms including calculation processing time.

Further, as shown in FIG. 2 (c), the correction coefficient K ₂ (= 1 / direct entry rate) of the injection pulse width with respect to the crank angle can be derived from the direct entry rate with respect to the crank angle. The correction coefficient K ₂ is corrected by an offset based on the rotational speed and a water temperature. When a predetermined amount of fuel is injected, the injection pulse width is multiplied by K ₂ (= 1 / direct injection rate). Thus, the direct injection rate is taken into consideration, and the amount of fuel introduced into the cylinder can be calculated appropriately. The correction coefficient K ₂ is converted into map data as a coefficient corresponding to the crank angle and used for fuel injection control.

  The additional injection permission crank angle is used in Example 1 to Example 3 described later, but in the case of Example 4, that is, in the case of high speed rotation, the direct injection rate itself is taken into consideration. The additional injection control is performed without using the additional injection permission crank angle.

  Next, some of the control methods of the fuel injection control device for an internal combustion engine according to the present invention will be described with reference to FIGS. 3 to 6, but before that, two basic suction modes used in each embodiment will be described. The atmospheric pressure prediction method (prediction means) will be described.

(Routine every 5ms)
In this intake pressure prediction method, the I / M pressure prediction value Pm (k) is calculated mainly based on the throttle opening TPS and the atmospheric pressure _Patm . In addition, the present intake pressure prediction method is also used to calculate the predicted I / M pressure at the end of the intake stroke in order to calculate the fuel amount of additional injection after the additional injection permission crank angle.

Specifically, ECU executes the present intake pressure prediction method for each 5 msec, the throttle valve opening the throttle opening detected by the sensor TPS, it reads the atmospheric pressure P _atm detected by the atmospheric pressure sensor, shown below The estimated I / M pressure value Pm (k) is calculated every 5 ms.

First, the basic opening area S0 of the throttle valve is calculated from the throttle opening TPS, and the pressure ratio between the basic opening area S0 and the atmospheric pressure P0 and the previous predicted I / M pressure Pm (k-1). The effective opening area S of the throttle valve is calculated from Pm (n) / P0 (effective opening area calculating means). The part for calculating the pressure ratio between the atmospheric pressure P0 and the predicted I / M pressure value Pm (k-1) corresponds to the pressure ratio detecting means.
S0 = Fa [TPS]
S = (1-aX) × S0
Here, a is a predetermined correction coefficient, and X is a pressure ratio Pm (n) / P0 between the atmospheric pressure P0 and the previous I / M pressure predicted value Pm (k-1).
Instead of the above, the effective area of the throttle can be obtained from a map data table for deriving the effective area of the throttle in accordance with the pressure ratio Pm (n) / P0 with respect to the TPS signal.
Here, the characteristic of the effective opening area S of the throttle valve with respect to the throttle opening TPS is affected by the pressure difference before and after the throttle. This phenomenon is presumed to have an effect on the effective opening area S because a turbulent flow is formed by separation of intake air at the edge portion of the throttle valve.

  When the internal combustion engine has the I / M pressure sensor 25 but does not have the atmospheric pressure sensor 23, the pressure in the intake pipe immediately after the ignition key is turned OFF → ON (before cranking) is detected. This can be used as atmospheric pressure. Alternatively, the intake pipe pressure can be used as the atmospheric pressure under operating conditions where the throttle opening is large and the intake pipe pressure is equivalent to full opening. Therefore, when the atmospheric pressure estimated before cranking is different from the atmospheric pressure estimated when the throttle opening is fully opened, the atmospheric pressure estimated before cranking is corrected by the atmospheric pressure estimated when the throttle opening is fully opened, or It may be replaced. That is, when the pressure ratio detecting means has both the atmospheric pressure sensor 23 and the I / M pressure sensor 25, the pressure ratio before and after the throttle valve 6 is detected using these, and the pressure ratio detecting means is detected by the atmospheric pressure sensor 23. Is not estimated, the pressure ratio around the throttle valve 6 is estimated using the I / M pressure sensor 25.

Next, the throttle passage intake air amount dP _th is calculated.
dP _th = S × P0 × Fv [Pm (k−1) / P _atm ] × K _AT
Here, K _AT is an intake air temperature correction coefficient, and Fv [Pm (k−1) / P _atm ] is map data for deriving a flow rate per unit area with respect to the pressure ratio [Pm (k−1) / P _atm ]. , Pm (k−1) is the previous I / M pressure prediction value.
The estimated intake air amount dP _e sucked into the cylinder is expressed by the following equation.
dP _e = K _MAP × Pm (k−1) × 5 / T _SGT
Here, K _MAP is a volumetric efficiency coefficient, and T _SGT is a required time for one stroke.

Therefore, the current I / M pressure predicted value Pm (k) is calculated from the following equation.
Pm (k) = Pm (k−1) + (dP _th −dP _e ) × Vc / Vm
Here, Vc is the cylinder volume, and Vm is the intake pipe volume.
It is assumed that the predicted I / M pressure value Pm (k) does not exceed the atmospheric pressure _Patm . Strictly speaking, the predicted I / M pressure value Pm (k) is corrected in consideration of the response delay of the sensor, but here it is omitted for simplicity.

(SGT routine)
The ECU executes the intake pressure prediction method for each stroke in parallel with the routine every 5 ms. Specifically, this intake pressure prediction method is performed in conjunction with the timing at which the SGT signal is output from the crank angle sensor, that is, 5 ° before the next stroke starts (SGT 5 ° B interruption). The I / M pressure Pb detected by the / M pressure sensor is read, and the predicted I / M pressure value Pb _etm after a predetermined number of strokes is calculated using the following formula.

First, an I / M pressure average value Pb _mean is obtained using a plurality of I / M pressures Pb measured during one stroke (stroke).
Pb _mean = ΣPb _i / i
Next, an I / M pressure change value dPm for one stroke is obtained from the following equation. At this time, the two I / M pressure predicted values Pm (k) and Pm (k−1) predicted by the routine every 5 ms are used before executing the intake pressure prediction method.
dPm = {Pm (k) −Pm (k−1)} × T _SGT / 5

Accordingly, the predicted I / M pressure value Pb _etm is calculated from the following equation.
Pb _etm = Pb _mean + G _etm × dPm (1)
Here, G _etm is a coefficient indicating the number of strokes. For example, if G _etm = 1.0, the I / M pressure predicted value Pb _etm after one stroke is predicted, and G _etm = 2.0. If so, the predicted I / M pressure value Pb _etm after two strokes is predicted.

Incidentally, I / M pressures predicted value Pb _etm shall not exceed the atmospheric pressure P _atm. Strictly speaking, the I / M pressure predicted value _{Pbetm needs} to be corrected in consideration of the response delay of the sensor and a predicted gain corresponding to the throttle opening TPS, but is omitted here for simplicity.
Next, each example using the prediction method will be described.

FIG. 3 is a diagram for explaining an example of fuel injection control in the fuel injection control device for an internal combustion engine according to the present invention.
Specifically, in a series of strokes of one cylinder, a change in intake pressure accompanying a change during a transition and a predicted value of the intake pressure are illustrated, and main injection (I) based on the predicted value and the like are added. A fuel amount setting and control method for injection (II) will be described.

In FIG. 3, SGT represents a signal output from the crank angle sensor and is output at every predetermined angle. By counting the SGT signal, the crank angle from the reference position is calculated, and a series of strokes (expansion, exhaust, intake, compression) is performed according to the crank angle.
TPS (the same applies to FIGS. 4, 5 and 6 described later) represents the opening degree of the throttle valve, and is controlled according to the accelerator opening degree. Will increase.

As described above, the ECU predicts the I / M pressure Pm after the next 5 ms every 5 ms by the routine every 5 ms, and the graph of the predicted I / M pressure value Pm is shown every 5 ms in FIG. It is a predicted value. Further, the ECU performs the SGT routine in parallel with the routine every 5 ms, and a graph of the intake pressure actual measurement value average Pb _mean during one stroke (SGT) calculated during the SGT routine is shown in FIG. It is a measured average value between SGTs. Note that the I / M pressure predicted value Pb _etm in the SGT routine may be used in place of the SGT actual measurement average value Pb _mean .

  In order to perform proper air-fuel ratio control, it is first necessary to accurately grasp the intake air amount at the end of the intake stroke. However, due to a sensor response delay or the like, instantaneous measurement of the intake air amount does not necessarily indicate a correct state. Therefore, the intake air amount has been predicted by using various means. The fuel injection control according to the present invention predicts the intake pressure at the end of the intake stroke as accurately as possible so as to derive the fuel injection amount based on it as accurately as possible, and further performs main injection and additional injection. Thus, fuel that is predicted to be insufficient at the time of acceleration is added to achieve a predetermined air-fuel ratio.

  The additional injection has been conventionally performed using various means. However, in the conventional technology, particularly when additional injection (asynchronous injection) is performed at an early timing, particularly in a low speed region, it has not been possible to cope with an increase in intake air amount. Therefore, in the present invention, the timing of the additional injection is delayed as much as possible, that is, by using the estimated intake pressure value at the timing as close to the end of the intake stroke as possible, it is possible to flexibly cope with an increase in intake air amount. It was. This late timing is the above-described additional injection permission crank angle θ.

A specific fuel injection control method will be described in more detail with reference to FIG.
The fuel amount of main injection (I) determines the injection pulse width using a conventional calculation method. For example, the actual measurement value Pb of the I / M pressure at the start of the exhaust stroke, the average measurement value at the point A, or the predicted value at the point B may be used. Here, the operating state is a steady state (TPS is constant), and the main injection fuel amount, that is, the injection pulse width is determined on the assumption that the intake pressure at this time is the intake pressure at the end of the intake stroke.

For example, when the measured value Pb of the I / M pressure at the start of the exhaust stroke is used, the fuel amount of the main injection (I), that is, the main injection pulse width T _inj1 is obtained by the following equation.
T _inj1 = K _inj × K _ev × Pb
Here, K _inj is a coefficient for converting the I / M pressure to the injection pulse width, and K _ev is a volumetric efficiency coefficient with respect to the I / M pressure. These coefficients are read and used as map data by the ECU.

Further, instead of the actual measurement value Pb of the I / M pressure, as shown in FIG. 8 to be described later, an air flow sensor 30 (intake air amount detecting means) for detecting the intake air amount flowing through the intake passage 3 is provided. The main injection pulse width T _inj1 may be calculated using the passing intake air amount Qb which is a value. In this case, it is obtained by the following formula.
T _inj1 = K _inj × Qb
Thus, the fuel of the main injection fuel amount set according to the operating state is injected into the intake air and supplied into the cylinder in synchronism with a predetermined crank angle (fuel injection control means).

  Next, additional injection (II) will be described. In the present invention, the amount of additional injected fuel is calculated based on the predicted value of the I / M pressure. By devising this calculation method, more accurate prediction, that is, more appropriate air-fuel ratio control is possible. It has become.

If the TPS changes significantly after the main injection, that is, if acceleration is requested, the amount of intake will naturally increase, so it is necessary to add fuel for an appropriate air-fuel ratio (to suppress the acceleration lean state). . Therefore, in the present invention, the difference ΔPm between the intake pressure predicted values (points C and D) of two neighboring 5 ms routines and the predicted value Pm (k) at the point D with respect to the additional injection permission crank angle θ. ) _{Is used} to calculate the predicted intake pressure Pm _etm at the point E at the end of the intake by the following formula (prediction means).
Pm _etm = Pm (k) + _ΔPm × K ₁ × T _SGT / 5
Here, K ₁ is a coefficient for correcting the prediction period.

Strictly speaking, since the predicted value needs to be corrected, the final fuel amount in the additional injection (II) is calculated using the corrected intake pressure (point F). This correction value Pb _etm is calculated by the following equation, assuming that the average pressure at point A is Pb _mean (n-1) and the predicted pressure at point B is Pm _SGT (n-1).
Pb _etm = Pm _etm + (Pb _mean (n-1) -Pm _SGT (n-1)) (2)
In the above formula, in order to make the predicted value more accurate, the difference between the measured value and the predicted value is used as the correction value.

Therefore, the additional injection pulse width ΔT _inj is obtained by the following equation, and additional injection is performed after the additional injection permission crank angle θ during the intake stroke (fuel injection control means).
ΔT _inj1 = K ₂ × {K _inj × K _ev × Pb _etm −T _inj1B } (3)
Here, K ₂ is a correction coefficient based on the direct injection rate described above, and T _inj1B is a correction _{obtained by reducing} the previous main injection pulse width T _inj1 based on the direct injection rate and the evaporative transport amount described later with reference to FIG. The pulse width corresponding to the amount actually introduced into the cylinder.

If the fuel injection control of the present embodiment is described in a simplified manner, the fuel injection amount (injection pulse width T _inj1 ) of the main injection (I) is calculated based on the measured value Pb of the I / M pressure at the start of the exhaust stroke. Thus, the amount of fuel injected (injection pulse width ΔT _inj1 ) of the additional injection (II) during the exhaust stroke is calculated by the difference _ΔPm between two predicted values every 5 ms in the vicinity of the additional injection permission crank angle θ. It is calculated based on the obtained ΔP ₂ and is injected into the intake during the intake stroke after the additional injection permission crank angle θ and introduced into the cylinder.

FIG. 4 is a diagram for explaining another example of the fuel injection control in the fuel injection control device for the internal combustion engine according to the present invention.
Since the additional injection of the present embodiment is the same as that of the first embodiment, a duplicate description is omitted.

In the present embodiment, the method for calculating the fuel amount of the main injection (I) is different from that in the first embodiment. Specifically, at the start of the exhaust stroke, the intake pressure _PbetmEX at the end of the intake stroke is calculated using equation (1) of the SGT routine described above. In other words, in equation (1), if the coefficient G _etm indicating the number of strokes is G _etm = G _etmEX = 2.0, the intake pressure Pb _etmEX after two strokes, that is, at the end of the intake stroke is predicted ( Prediction means).
Pb _etmEX = Pb _mean + G _etmEX × dPm
However, in the case of the present embodiment shown in FIG. 4, since the operation state at the start of the exhaust stroke is a steady state and dPm = 0, Pb _etmEX = Pb _mean , and the measured value average Pb _mean at point A is used. Thus, the fuel amount of the main injection (I) is calculated. Strictly speaking, the Pb _etmEX is corrected using the expression (2) in the first embodiment.
Accordingly, the injection pulse width T _inj2 of the main injection (I) is obtained by the following equation, and is injected into the intake air and supplied into the cylinder in synchronism with a predetermined crank angle (fuel injection control means).
T _inj2 = K _inj × K _ev × Pb _etmEX

Then, the injection pulse width ΔT _inj2 of the additional injection (II) is obtained by using T _inj2B obtained by reducing the amount of T _inj2 based on the direct _injection rate and the evaporation transport amount in the equation (3) of the first embodiment.
ΔT _inj2 = K ₂ × {K _inj × K _ev × Pb _etm −T _inj2B }

If the fuel injection control of this embodiment is described in a simplified manner, the injected fuel amount (injection pulse width T _inj2 ) of the main injection (I) is based on the predicted value Pb _etmEX of the I / M pressure at the start of the exhaust stroke. It is calculated and injected into the intake air during the exhaust stroke, and the injected fuel amount (injection pulse width ΔT _inj2 ) of the additional injection (II) is a _{difference ΔPm} between two predicted values every 5 ms near the additional injection permission crank angle θ, etc. Is calculated based on ΔP ₂ obtained by the above, and injected during the intake stroke after the additional injection permission crank angle θ and introduced into the cylinder.

Unlike the first embodiment, the present embodiment uses the predicted value for calculating the fuel amount of the main injection, so that the fuel amount of the additional injection can be reduced as much as possible during a transition, particularly during acceleration. Become. In other words, by making the additional injection fuel amount during the intake stroke as small as possible, the additional injection permission crank angle θ can be made as late as possible, and the fuel amount of the additional injection can be injected based on more accurate intake pressure prediction. Thus, the air-fuel ratio control can be performed as intended.
Instead of the intake pressure _PbetmEX at the end of the intake stroke described above, the average intake amount during one stroke (for example, the exhaust stroke) by the air flow sensor 30 (see FIG. 8) and the in-cylinder intake amount during one stroke are changed. The in-cylinder intake amount at the end of the intake stroke may be predicted using the change amount (see the prediction means, equation (1 ′) in Embodiment 6). Then, a main injection fuel amount, that is, a main injection pulse width is calculated based on the predicted in-cylinder intake amount, and is injected into the intake air and supplied into the cylinder in synchronism with a predetermined crank angle (fuel). Injection control means).

FIG. 5 is a diagram for explaining another example of the fuel injection control in the fuel injection control device for the internal combustion engine according to the present invention.
Since the main injection is the same as that in the second embodiment, a duplicate description is omitted.

  In the present embodiment, in order to follow a sudden increase in intake air amount particularly during sudden acceleration, additional injection is performed in a plurality of times (twice), and during the intake stroke described in the first embodiment. The additional injection is the second additional injection, and the first additional injection is performed between the main injection and the second additional injection.

Specifically, the amount of change ΔPm−1 of the intake pressure prediction values (points G and C) of the latest two 5-ms routines before the start of the intake stroke, the intake pressure actual measurement value average Pb _mean during the exhaust stroke, The predicted intake pressure _PbetmIN at the point H at the end of the intake stroke is calculated using the above-described equation (1) of the SGT routine (prediction means).
Pb _etmIN = Pb _mean + G _etmIN × _ΔPm -1
Here, G _etmIN = 1.0 is set to predict the intake pressure one stroke ahead, that is, at the end of the intake stroke. Strictly speaking, the _PbetmIN is corrected using the expression (2) in the first embodiment.
Therefore, the fuel amount (first fuel amount) of the first additional injection (II), that is, the injection pulse width ΔT _inj3 is based on the predicted intake pressure Pm _etmIN (first intake amount) at the H point at the end of intake. It is obtained by the following formula, and additional injection is performed before the start of the intake stroke (fuel injection control means).
ΔT _inj3 = K ₂ × (K _inj × K _ev × Pb _etmIN −T _inj3B )
Here, T _inj3B is obtained by correcting the decrease in the immediately preceding main injection pulse width T _{inj3 based} on the direct injection rate and the evaporation transport amount.

Further, the fuel amount of the second additional injection (III), that is, the injection pulse width ΔT _inj4 is obtained by the following equation based on the predicted intake pressure Pm _etmIN (second intake amount) at the point E at the end of intake. Additional injection is performed after the additional injection permission crank angle θ during the intake stroke (fuel injection control means).
ΔT _inj4 = K ₂ × (K _inj × K _ev × Pb _etmIN −T _inj3B −ΔT _inj3B )
Here, _PbetmIN in the _equation is the amount of change ΔPm−1 of the intake pressure predicted values (points C and D) of the two 5-ms routines in the vicinity of the additional injection permission crank angle θ and the intake pressure actual measurement during the exhaust stroke. The predicted intake pressure Pm _etmIN at the point E at the end of the intake stroke is calculated using the value average Pb _mean and the above-described SGT routine (1) (prediction means).

If the fuel injection control of this embodiment is described in a simplified manner, the injected fuel amount (injection pulse width T _inj3 ) of the main injection (I) is based on the predicted value Pb _etmEX of the I / M pressure at the start of the exhaust stroke. It is calculated and injected into the intake air during the exhaust stroke, and the injected fuel amount (injection pulse width ΔT _inj3 ) of the first additional injection (II) is the difference ΔPm− between two predicted values every 5 ms before the start of the intake stroke. It is calculated based on ΔP ₂ at the end of the intake stroke obtained by 1 etc., and is injected into the intake air at the start of the intake stroke, and the amount of injected fuel (injection pulse width ΔT _inj4 ) of the second additional injection (III) is , Calculated based on ΔP ₃ at the end of the intake stroke obtained by the difference ΔPm between two 5 ms prediction values in the vicinity of the additional injection permission crank angle θ, and inhaled during the intake stroke after the additional injection permission crank angle θ. It is injected into the cylinder and introduced into the cylinder.

  As described above, by performing the additional injection a plurality of times, even when the engine speed is high to some extent, it is possible to flexibly cope with a sudden increase in the intake air amount without causing an air-fuel ratio error.

FIG. 6 is a diagram for explaining another example of the fuel injection control in the fuel injection control device for the internal combustion engine according to the present invention.
In addition, although either method of Example 1 or Example 2 may be used about main injection, in FIG. 6, it is the same as that of Example 1 for convenience, and the overlapping description is abbreviate | omitted.

  This embodiment shows a fuel injection control during high-speed rotation, particularly a control method for additional injection. This is because when the engine rotates at high speed, the crank angle interruption processing increases and the CPU load is high, and the cycle of crank angle conversion becomes long to perform the routine every 5 ms, and the demand for control accuracy is low. Therefore, the following fuel injection control is performed.

  In this embodiment, when the rotational speed of the engine is larger than the predetermined rotational speed (when the cycle of converting the crank angle of the routine every 5 ms is larger than the crank angle during one stroke, specifically, 3900 rpm, etc.) The fuel injection control is performed by predicting the intake pressure at the end of the intake stroke based on the SGT routine described above without performing the routine every 5 ms used in Examples 1-3. Specifically, before the start of the intake stroke, the intake pressure at the end of the intake stroke is predicted from the amount of change in I / M pressure during one stroke based on the SGT routine. After the prediction, the prediction is made every 5 ms by the routine every 5 ms. I / M pressure prediction is prohibited. Then, the additional injection amount is determined based on the predicted intake pressure by the SGT routine, the additional injection is performed after the start of the intake stroke, and the additional injection process after the additional injection is prohibited.

Specifically, if the measured value of the I / M pressure at point I at the start of the exhaust stroke is taken as the measured value of the I / M pressure at point J at the start of the intake stroke, the intake pressure change dPr during one stroke is It becomes the following formula.
dPr = Pb (n) -Pb (n-1)
Further, the predicted intake pressure _PmetmIN at the point L at the end of the intake stroke is obtained from the following equation using the above-described equation (1) of the SGT routine.
Pb _etmIN = Pb _mean + G _etmIN × dPr
Here, _GetmIN = 1.0 is set, and the intake pressure at the end of one stroke, that is, at the end of the intake stroke is predicted.
Therefore, the fuel amount of the additional injection (II), that is, the injection pulse width ΔT _inj5 is obtained by the following equation.
ΔT _inj5 = K ₂ × (K _inj × K _ev × Pb _etmIN −T _inj5B )
Here, T _inj5B is obtained by correcting the decrease in the immediately preceding main injection pulse width T _{inj5 based} on the direct injection rate and the evaporation transport amount.

If the fuel injection control of this embodiment is described in a simplified manner, the injected fuel amount (injection pulse width T _inj5 ) of the main injection (I) is the measured value Pb (n−1) of the I / M pressure at the start of the exhaust stroke. ) And is injected into the intake air during the exhaust stroke, and the amount of injected fuel (injection pulse width ΔT _inj5 ) of the additional injection (II) is the measured value of the I / M pressure at the point I at the start of the exhaust stroke. It is calculated on the basis of ΔP ₂ obtained by the difference dPr between the Pb (n−1) and the actual measured value Pb (n) of the I / M pressure at the point J at the start of the intake stroke, and is calculated during the intake stroke. It is injected and introduced into the cylinder.
When performing the fuel injection control of the third embodiment, if the engine speed is higher than the predetermined engine speed, the prediction of the estimated intake pressure _PbetmIN at the point E at the end of the intake stroke is prohibited, or the second addition The injection (III) may be prohibited.

  FIG. 7 is a view for explaining fuel adhesion and evaporative transport in the fuel injection control device for an internal combustion engine according to the present invention.

  For comparison, FIG. 7A shows the transition of the air-fuel ratio during rapid acceleration when there is no asynchronous injection (main injection only) and when there is asynchronous injection in the conventional fuel injection control method.

  As shown in FIG. 7 (a), when there is no asynchronous injection, the fuel amount cannot be increased with respect to the increase in the intake air amount at the time of transition, particularly at the time of acceleration. There was also a risk of misfire. In addition, when only asynchronous injection is performed, the lean state at the time of acceleration is somewhat suppressed. However, due to the influence of asynchronous injection, it becomes rich after that, and the same air-fuel ratio control cannot be performed. It was. This is because, as in the case of the main injection, the fuel of the additional injection is not directly transported into the cylinder because it becomes a liquid film adhering to the inner wall of the intake pipe, and this liquid film evaporates and transports after the next intake stroke. This is because it is introduced into the cylinder.

  Therefore, in the present invention, as shown in the lower diagram of FIG. 7 (b), the amount of liquid film adhering to the inner wall of the intake pipe is taken into consideration, and the amount evaporated and transported from there to the cylinder is reduced from the next main injection fuel amount. By correcting, the lean state and rich state are suppressed, and more ideal air-fuel ratio control is performed.

  Specifically, the amount of liquid film remaining on the inner wall is calculated from the previous main injection fuel amount and its direct injection rate, and includes the previous additional injection fuel amount (including the case of performing multiple additional injections in Example 3) and The liquid film amount remaining on the inner wall is calculated from the direct entry rate, and the total liquid film amount is calculated as accurately as possible by taking into account the amount of liquid film remaining on the inner wall. Calculation means). By calculating the amount of evaporative transport that is evaporated and transported during the intake stroke from the calculated liquid film amount, and by correcting the amount to be reduced in consideration of the amount of evaporative transport during the main injection in the next stroke, more accurate Air-fuel ratio control is realized (fuel injection control means). In the present invention, not only the evaporative transport amount from the liquid film due to the main injected fuel amount but also the evaporative transport amount from the liquid film due to the additional injected fuel amount is also considered, so that the more accurate liquid film amount and evaporation can be achieved. Transport volume can be predicted.

  Therefore, strictly speaking, in the main injection fuel amount of each of the above-described embodiments, a fuel amount that has been corrected for reduction is used. In particular, in the case of the fuel injection control according to the present invention, since the timing of additional injection is delayed as much as possible in order to follow the change in intake air amount as much as possible, additional injection may be performed at a low direct injection rate. It is very important to predict the amount of evaporative transport from the liquid film by volume and to compensate for its reduction. It should be noted that this reduction correction calculation may be performed between the last additional injection and the next main injection in the same cylinder, and is accurate considering the previous main injection, the fuel amount of the additional injection, the direct injection rate at that time, and the like. The amount of evaporative transport is calculated.

(Modification)
When calculating the predicted I / M pressure value, in the above-described embodiment, the predicted I / M pressure value is calculated using the detection values from each sensor in the two prediction routines, the routine every 5 ms and the SGT routine. However, instead of the I / M pressure sensor, an airflow sensor 30 (intake amount detection means) for detecting the intake amount flowing in the intake passage 3 is provided, and an intake amount prediction is performed using a detection value from the airflow sensor 30. A value may be obtained. As with the I / M pressure, an appropriate injected fuel amount can be calculated from the intake air amount, and the above-described fuel injection control can be performed.

FIG. 8 is a configuration diagram showing a modification of the embodiment of the internal combustion engine and the fuel injection control device thereof according to the present invention.
The configuration of the internal combustion engine shown in FIG. 8 is different from the configuration of FIG. 1 in that an air flow sensor 30 is provided upstream of the throttle valve 6 instead of the I / M pressure sensor 25. Therefore, the configuration other than the air flow sensor 30 of the internal combustion engine shown in FIG. 8 is the same as the configuration of FIG.
Hereinafter, a method of obtaining the predicted intake air amount using the detection value from the airflow sensor 30 will be described.

(Routine every 5ms)
This intake air quantity estimation method is mainly based on the atmospheric pressure P _atm detected by the throttle opening TPS and the atmospheric pressure sensor, and calculates the intake air amount predicted value dGe a (k). In addition, since this intake air amount prediction method calculates the fuel amount of additional injection after the additional injection permission crank angle, it can also be used to calculate the predicted intake air amount at the end of the intake stroke.

Specifically, ECU executes the present intake air amount prediction method for each 5 msec, the throttle valve opening the throttle opening detected by the sensor TPS, it reads the atmospheric pressure P _atm detected by the atmospheric pressure sensor, shown below The estimated I / M pressure value Pm (k) is calculated every 5 ms.

First, the effective area of the throttle is obtained from the TPS signal detected by the throttle valve opening sensor, that is, the map data table storing the actual value of the effective area of the throttle according to the voltage value of the TPS (effective opening area). Calculation means).
S = Farea [V _TPS ]
Instead of the above, the basic opening area S0 of the throttle valve is calculated from the throttle opening TPS, and further, the basic opening area S0, the atmospheric pressure P0, and the previous estimated intake pipe pressure Pm (k-1). The effective opening area S of the throttle valve may be calculated from the pressure ratio Pm (n) / P0. Here, the part for calculating the pressure ratio between the atmospheric pressure P0 and the estimated intake pipe pressure Pm (k-1) corresponds to the pressure ratio detecting means.
S0 = Fa [TPS]
S = (1-aX) × S0
Here, a is a predetermined correction coefficient, and X is a pressure ratio Pm (n) / P0 between the atmospheric pressure P0 and the previous estimated intake pipe pressure Pm (k-1). A method of calculating the intake pipe internal pressure estimated value Pm will be described later.
Here, the characteristic of the effective opening area S of the throttle valve with respect to the throttle opening TPS is affected by the pressure difference before and after the throttle. This phenomenon is presumed to have an effect on the effective opening area S because a turbulent flow is formed by separation of intake air at the edge portion of the throttle valve.

Next, the throttle passage intake air amount dG _th is calculated.
dG _th = S × [P _atm / 760] × Fv [Pm (k−1) / P _atm ] × K _AT
Here, K _AT is an intake air temperature correction coefficient, and Fv [Pm (k−1) / P _atm ] is map data for deriving a flow rate per unit area with respect to the pressure ratio [Pm (k−1) / P _atm ]. , Pm (k−1) is the previous estimated intake pipe pressure value.
The estimated intake air amount dG _e sucked into the cylinder is expressed by the following equation.
dG _e = K _MAP × Pm (k−1) × 5 / T _SGT
Here, K _MAP is a volumetric efficiency coefficient, and T _SGT is a required time for one stroke.

The current intake pipe internal pressure estimated value Pm (k) is calculated from the following equation.
Pm (k) = Pm (k−1) + Km (dG _th −dG _e ) × Vc / Vm
Here, Km is a conversion coefficient for converting from mass to pressure, Vc is a cylinder volume, and Vm is an intake pipe volume.
That is, when the pressure ratio detection means does not have the I / M pressure sensor 25 (see FIG. 1) but has the atmospheric pressure sensor 23 and the air flow sensor 30, the pressures before and after the throttle valve 6 are determined using the above procedure. Estimating the ratio, the intake amount is estimated.

(SGT routine)
The ECU executes the intake air amount prediction method for each stroke in parallel with the routine every 5 ms. Specifically, the intake air amount prediction method is performed in conjunction with the timing at which the SGT signal is output from the crank angle sensor, that is, 5 ° before the next stroke starts (SGT 5 ° B interruption), and the air flow It reads the detected intake air amount G _afs by the sensor 30, using the formula shown below, calculates the intake air amount predicted value Ge _etm after a predetermined number of strokes.

First, an average intake air amount dG _afs (n) during one stroke is obtained using a plurality of intake air amounts _Gafs measured during one stroke (stroke).
dG _afs (n) = ΣG _afs (k) / m
Here, m is the number of times measured by the airflow sensor 30 during one stroke.
Further, the average intake air amount dG _afs (n) during one stroke is converted into the in-cylinder intake air amount G _afs (n).
G _afs (n) = K × G _afs (n−1) + (1−K) × dG _afs (n)
Next, the average estimated intake air amount Ge _AVE of the estimated intake air amount dG _e during one stroke determined by the routine for every 5 ms is obtained from the following formula together with the air flow sensor 30.
Ge _AVE (n) = (ΣdG (k) / L) × T _SGT / 5
Here, L is the estimated number of intake air amounts during one stroke.

The intake air amount change ΔGe between 180 ° CA is calculated from the following equation.
ΔGe = {Ge (k) −Ge (k−1)} × T _SGT / 5
Further, the average delay ΔG _{AVE for} one stroke is calculated by the following equation.
ΔG _AVE = Ge (n) −Ge _AVE (n)

In SGT routine, the estimated intake air amount when the intake stroke ends of the 545 ° B point for a given cylinder Ge _EtmEX, and the estimated intake air amount Ge _ETmin when the intake stroke ends of the 365 ° B point of the other cylinders, respectively are calculated.
The estimated intake air amount Ge _etmEX at the end of the intake stroke at the time of 545 ° B is calculated by the following equation.
Ge _etmEX = G _afs + ΔG _AVE + K _etmEX × ΔGe
Further, the estimated intake air amount Ge _etmIN at the end of the intake stroke at the time of 365 ° B is calculated by the following equation.
_{Ge etmIN = G afs + ΔG AVE} + K etmIN × ΔGe (1 ')
Here, G _afs is the average intake amount obtained from the air flow sensor 30, ΔG _AVE is the response delay due to the average, K is the prediction gain, K _etmEX = 2.0, and K _etmIN = 1.0, and ΔGe is the rate of change in the intake air amount during one stroke.

Note that while the target value of the electronically controlled throttle valve is being opened to the opening side from the present time, the prediction of the intake air amount is insufficient, so the prediction gain needs to be increased.
For example, when the following equation is established, the gain is increased by setting the gain K as a predetermined multiple.
TPS _obj ≧ TPS (n) + predetermined value

  Next, the additional injection (II) in FIG. 3 of the first embodiment or FIG. 4 of the second embodiment using the estimated intake air amount described above will be described. In this modification, more accurate prediction, that is, more appropriate air-fuel ratio control is possible, as in the case where the additional injected fuel amount is calculated based on the predicted value of the I / M pressure.

If the TPS changes significantly after the main injection, that is, if acceleration is requested, the amount of intake will naturally increase, so it is necessary to add fuel for an appropriate air-fuel ratio (to suppress the acceleration lean state). . Therefore, in the present invention, with reference to the additional injection permission crank angle θ, the difference ΔGe between the estimated intake air amount values (C point and D point) of the two preceding and following 5 ms routines and the predicted value Ge (k of the D point) ), The estimated intake air amount Ge _etm at the end point E of intake is calculated by the following equation.
Ge _etm = Ge (k) + ΔGe × K ₃ × T _SGT / 5
Here, K ₃ is a coefficient for correcting the prediction period.

Strictly speaking, since the estimated value needs to be corrected, the final additional injected fuel amount (II) is calculated using the corrected estimated intake air amount (point F). This correction value Ge _etm is calculated by the following equation, assuming that the average intake air amount at point A based on the detection value of the air flow sensor 30 is G _afs (n−1) and the estimated intake air amount G _SGT (n−1) at point B. Is done.
_{Ge etm = Ge etm + (G} afs (n-1) -G SGT (n-1))
In the above formula, in order to make the predicted value more accurate, the difference between the measured value and the predicted value is used as the correction value.

Therefore, the additional injection pulse width ΔT _inj1 is _expressed by the following equation.
ΔT _inj1 = K ₄ × {K _inj × Ge _etm −T _inj1B } (3 ′)
Here, K ₄ is a correction coefficient based on the direct injection rate described above, and T _inj1B is a correction _{obtained by reducing} the previous main injection pulse width T _inj1 based on the direct injection rate and the evaporation transport amount described in FIG. The pulse width corresponding to the amount actually introduced into the cylinder.

If the fuel injection control of this modification is simplified and described, the injected fuel amount (injection pulse width T _inj1 ) of the main injection (I) is calculated based on the estimated intake air amount Ge at the start of the exhaust stroke, and the exhaust gas is controlled. The injected fuel amount (injection pulse width ΔT _inj1 ) injected during intake during the stroke is calculated based on the difference ΔGe between the estimated intake amounts for every 5 ms in the vicinity of the additional injection permission crank angle θ. Then, during the intake stroke after the additional injection permission crank angle θ, it is injected into the intake air and introduced into the cylinder.

  Further, additional injection (II) and (III) of the third embodiment (see FIG. 5) using the estimated intake air amount will be described below.

In this case, the amount of change in the estimated intake air amount (G point, C point) of the latest two 5-ms routines before the start of the intake stroke, the average intake air amount _Gafs during the exhaust stroke, and ( The predicted intake air amount Ge _etmIN at the point H at the end of the intake stroke is calculated using the equation 1 ′) (prediction means).
_{Ge etmIN = G afs + ΔG AVE} + K etmIN × ΔGe
Here, K _etmIN = 1.0 is set to predict the intake amount one stroke ahead, that is, at the end of the intake stroke.
Therefore, the fuel amount (first fuel amount) of the first additional injection (II), that is, the injection pulse width ΔT _inj3, is based on the predicted intake amount Ge _etmIN (first intake amount) at the H point at the end of intake. It is obtained by the following formula, and additional injection is performed before the start of the intake stroke (fuel injection control means).
ΔT _inj3 = K ₄ × (K _inj × Ge _etmIN −T _inj3B )
Here, T _inj3B is obtained by correcting the decrease in the immediately preceding main injection pulse width T _{inj3 based} on the direct injection rate and the evaporation transport amount.

Further, the fuel amount (second fuel amount) of the second additional injection (III), that is, the injection pulse width ΔT _inj4, is based on the predicted intake amount Ge _etmIN (second intake amount) at the point E at the end of intake. The additional injection is performed after the additional injection permission crank angle θ during the intake stroke (fuel injection control means).
ΔT _inj4 = K ₄ × (K _inj × Ge _etmIN −T _inj3B −ΔT _inj3B )
Here, Ge _etmIN in the _equation is the amount of change in the estimated intake air amount (point C, point D) of the two 5-ms routines in the vicinity of the additional injection permission crank angle θ, the average intake air amount G _afs during the exhaust stroke, The predicted intake air amount Ge _etmIN at the point E at the end of the intake stroke is calculated using the equation (1 ′) of the SGT routine described above (prediction means).

If the fuel injection control of this embodiment is described in a simplified manner, the injected fuel amount (injection pulse width T _inj3 ) of the main injection (I) is calculated based on the estimated intake air amount Ge at the start of the exhaust stroke, and the exhaust gas is controlled. The injected fuel amount (injection pulse width ΔT _inj3 ) injected into the intake air during the stroke is calculated based on the difference ΔGe between the estimated intake air amounts every two 5 ms before the start of the intake stroke. The injected fuel amount (injection pulse width ΔT _inj4 ) of the second additional injection (III) at the start of the intake stroke is the estimated intake amount every two 5 ms in the vicinity of the additional injection permission crank angle θ. Is calculated based on the difference ΔGe, and is injected into the intake during the intake stroke after the additional injection permission crank angle θ and introduced into the cylinder.

It is a block diagram which shows an example of embodiment of the internal combustion engine which concerns on this invention, and its fuel-injection control apparatus. It is a figure explaining the direct injection rate in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a figure explaining an example (Example 1) of the fuel-injection control in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a figure explaining other examples (Example 2) of the fuel-injection control in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a figure explaining other examples (Example 3) of the fuel-injection control in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a figure explaining other examples (Example 4) of the fuel-injection control in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a figure explaining the reduction | decrease correction | amendment by the evaporative transport amount in the fuel-injection control apparatus of the internal combustion engine which concerns on this invention. It is a block diagram which shows the modification of embodiment of the internal combustion engine which concerns on this invention, and its fuel-injection control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Air cleaner 3 Intake passage 4 Surge tank 5 Intake manifold 6 Throttle valve 7 Fuel injection valve 8 Intake port 9 Exhaust passage 10 Spark plug 11 Exhaust port 21 ECU
22 Accelerator opening sensor 23 Atmospheric pressure sensor 24 Throttle valve opening sensor 25 I / M pressure sensor 26 Crank angle sensor 27 Water temperature sensor 28 Step motor 30 Air flow sensor

Claims (9)

Throttle opening detection means for detecting the opening of the throttle disposed in the intake passage of the internal combustion engine;
Effective opening area calculating means for calculating the effective opening area of the throttle according to the opening of the throttle detected by the throttle opening detecting means;
Fuel injection control means for setting a main injection fuel amount in accordance with an operating state, and supplying fuel of the main injection fuel amount during intake in synchronization with a predetermined crank angle;
Pressure ratio detecting means for detecting or estimating the pressure ratio before and after the throttle;
Using the pressure ratio detected or estimated by the pressure ratio detecting means and the effective opening area by the effective opening area calculating means, the intake pressure or in-cylinder intake amount in the intake passage on the downstream side of the throttle is determined every predetermined time. A prediction means for predicting
An additional injection permitting crank angle setting means for setting a crank angle permitting additional injection based on the direct fuel injection rate during the intake stroke;
The predicting means predicts an intake pressure or in-cylinder intake amount at the end of the intake stroke based on a change in intake pressure or in-cylinder intake amount predicted in the vicinity of the additional injection permission crank angle;
The internal combustion engine, wherein the fuel injection control means additionally injects an additional injected fuel amount calculated based on the predicted intake pressure or in-cylinder intake amount after the additional injection permission crank angle during an intake stroke. Fuel injection control device. The fuel injection control device for an internal combustion engine according to claim 1,
The pressure ratio detection means includes an intake passage pressure detection means for detecting an intake pressure in the intake passage downstream of the throttle,
The predicting means uses the average pressure during one stroke of the intake pressure detected by the intake passage pressure detecting means and the amount of change in the intake pressure predicted before the start of the intake stroke, and the intake air at the end of the intake stroke Predict the pressure,
The fuel injection control device for an internal combustion engine, wherein the fuel injection control means sets the main fuel injection amount based on a predicted intake pressure. The fuel injection control device for an internal combustion engine according to claim 2,
When the rotational speed of the internal combustion engine is equal to or higher than a predetermined rotational speed,
The predicting means predicts the intake pressure at the end of the intake stroke using the average pressure of the intake pressure by the intake passage pressure detecting means during one stroke and the amount of change in the intake pressure predicted before the start of the intake stroke. ,
The fuel injection control means controls to additionally inject the fuel amount calculated based on the predicted intake pressure before the start of the intake stroke,
Inhibition of intake pressure after predicting the intake pressure at the end of the intake stroke before the start of the intake stroke by the predicting means, or additional injection after the additional injection after the start of the intake stroke by the fuel injection control means is prohibited. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1,
The pressure ratio detecting means includes an intake air amount detecting means for detecting an intake air amount flowing through the intake passage,
The predicting means uses the average intake air amount during one stroke of the intake air amount by the intake air amount detecting means and the change amount of the in-cylinder intake air amount estimated before the start of the intake stroke, and the in-cylinder at the end of the intake stroke Predict the intake volume,
The fuel injection control device for an internal combustion engine, wherein the fuel injection control means sets the main injection fuel amount based on a predicted in-cylinder intake amount. The fuel injection control device for an internal combustion engine according to claim 1,
The fuel injection control means includes a fuel adhesion amount calculation means for calculating an adhesion amount of fuel adhering to the wall surface of the intake passage based on a main injection fuel amount and its direct injection rate and an additional injection fuel amount and its direct injection rate. ,
The fuel injection control device for an internal combustion engine, wherein the fuel injection control means corrects the current main injection fuel amount by a reduced amount by evaporating and transporting from the previous fuel adhesion amount by the fuel adhesion amount calculation means. The fuel injection control device for an internal combustion engine according to claim 1,
The pressure ratio detection means includes an intake passage pressure detection means for detecting an intake pressure in the intake passage downstream of the throttle,
The predicting means uses the average pressure during one stroke of the intake pressure detected by the intake passage pressure detecting means and the predicted amount of change in the intake pressure before the start of the intake stroke, and uses the average pressure at the end of the intake stroke. 1 Predict the intake pressure,
The fuel injection control means controls to additionally inject the first fuel amount calculated based on the predicted first intake pressure before or after the start of the intake stroke,
The predicting means predicts a second intake pressure at the end of the intake stroke based on a change amount of the intake pressure predicted in the vicinity of the additional injection permission crank angle,
The fuel injection control means controls to additionally inject the second fuel amount calculated based on the predicted second intake pressure after the additional injection permission crank angle during the intake stroke.
A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 6,
When the rotational speed of the internal combustion engine is equal to or higher than a predetermined rotational speed,
A fuel injection control device for an internal combustion engine, which prohibits the prediction of the second intake pressure by the prediction means or the additional injection of the second fuel amount by the fuel injection control means. The fuel injection control device for an internal combustion engine according to claim 6,
The fuel injection control means calculates the amount of fuel adhering to the wall surface of the intake passage based on the main injection fuel amount, the direct injection rate, the first fuel amount, the direct injection rate, the second fuel amount, and the direct injection rate. A fuel adhesion amount calculating means for
The fuel injection control device for an internal combustion engine, wherein the fuel injection control means corrects the current main injection fuel amount by a reduced amount by evaporating and transporting from the previous fuel adhesion amount by the fuel adhesion amount calculation means. The fuel injection control device for an internal combustion engine according to claim 1,
The pressure ratio detecting means includes an intake air amount detecting means for detecting an intake air amount flowing through the intake passage;
The predicting means uses the average intake air amount during one stroke of the in-cylinder intake air amount detected by the intake air amount detecting means and the predicted change amount of the in-cylinder intake air amount before the start of the intake stroke. Predict the first intake volume at the end,
The fuel injection control means controls to additionally inject the first fuel amount calculated based on the predicted first intake amount before the start of the intake stroke, and
The predicting means predicts a second intake amount at the end of the intake stroke based on a change amount of the in-cylinder intake amount predicted in the vicinity of the additional injection permission crank angle,
The fuel injection control means controls to additionally inject the second fuel amount calculated based on the predicted second intake amount after the additional injection permission crank angle during the intake stroke;
A fuel injection control device for an internal combustion engine.

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