JP2009191662A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine capable of exactly supplying a fuel quantity required for the internal combustion engine, by maximally providing an advantage by cylinder injection such as an improvement in the filling ratio of fuel and restraint of knocking by cooling of intake air, by maximally performing the cylinder injection. <P>SOLUTION: A request fuel quantity GCYL is calculated in response to an engine speed NE and a load AP of the internal combustion engine 3, and a limit value GCYLD_LMTH/L of a cylinder injection quantity by a cylinder fuel injection valve 6 is set in response to the engine speed of the internal combustion engine 3. An injection mode is set in a cylinder injection mode of injecting the fuel only from the cylinder fuel injection valve 6 when the request fuel quantity GCYL is this limit value or less, and the injection mode is set in a cylinder port injection mode of injecting the fuel from both the fuel injection valves 6 and 8 when the request fuel quantity GCYL is larger than the limit value. A cylinder injection quantity GCYLD#n and a port injection quantity GCYLP#n are calculated in response to the request fuel quantity GCYL and the injection mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine having an in-cylinder fuel injection valve for injecting fuel into a cylinder and a port fuel injection valve for injecting fuel into an intake port.

  Conventionally, as a fuel injection control device for this type of internal combustion engine, for example, one disclosed in Patent Document 1 is known. In this internal combustion engine, homogeneous combustion is performed at high rotation and high load, and stratified combustion is performed at low rotation and low load. During stratified combustion, fuel is injected from the in-cylinder fuel injection valve into the combustion chamber during the compression stroke. On the other hand, during homogeneous combustion, fuel is injected from the port fuel injection valve into the intake port during the intake stroke. During homogeneous combustion, a very small amount of fuel is supplementarily injected from the in-cylinder fuel injection valve during the compression stroke. Thereby, the cooling effect due to the vaporization of the fuel prevents the tip portion of the in-cylinder fuel injection valve from being overheated and suppresses deposits and the like from being deposited on the nozzle hole due to overheating.

  When in-cylinder injection by the in-cylinder fuel injection valve is compared with port injection by the port fuel injection valve, the former directly injects the fuel into the cylinder, so there is very little fuel waste and a high fuel filling rate. At the same time, the cooling due to the vaporization of the fuel is performed exclusively on the intake air sucked into the cylinder, so that the temperature of the air-fuel mixture at the end of the compression stroke is sufficiently lowered to effectively knock at high loads. It has the advantage that it can be suppressed. On the other hand, in the conventional fuel injection control apparatus described above, during homogeneous combustion, most of the fuel is injected by port injection, and in-cylinder injection is only used to supply a very small amount of fuel. For this reason, the advantages of the above-described in-cylinder injection can hardly be obtained. In particular, in this fuel injection control device, since the homogeneous combustion is performed at the time of high load and high rotation, knocking that tends to occur at that time cannot be sufficiently suppressed.

  The present invention has been made to solve the above-described problems. By performing in-cylinder injection as much as possible, in-cylinder injection such as improvement in fuel filling rate and suppression of knocking due to intake air cooling is performed. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can obtain the maximum advantage of the above and can supply the fuel amount required for the internal combustion engine without excess or deficiency.

JP 2002-364409 A

  In order to achieve the above object, the invention according to claim 1 of the present application is an internal combustion engine having an in-cylinder fuel injection valve 6 for injecting fuel into the cylinder 3a and a port fuel injection valve 8 for injecting fuel into the intake port 3f. A fuel injection control device 1 for an engine 3, which is a rotational speed detection means (in the embodiment (hereinafter referred to as “this”)) for detecting the rotational speed of the internal combustion engine 3 (the engine rotational speed NE in the embodiment (hereinafter the same in this section)). The same applies in the section) Crank angle sensor 21), load detecting means (accelerator opening sensor 22) for detecting the load (accelerator opening AP) of the internal combustion engine 3, and the detected rotational speed and load of the internal combustion engine. The required fuel amount calculating means (ECU 2, step 21 in FIG. 6) for calculating the required fuel amount GCYL required for the internal combustion engine 3 and the in-cylinder fuel injection valve 6 are injected according to the rotational speed of the internal combustion engine 3. Limit value setting means (ECU 2, steps 31 to 34 in FIG. 7) for setting limit values (upper limit value GCYLD_LMTH, upper limit value GCYLD_LMTL) of the in-cylinder injection amount, and a cylinder in which the calculated required fuel amount GCYL is set When the internal injection amount is less than or equal to the limit value, the injection mode is set to an in-cylinder injection mode in which fuel is injected only from the in-cylinder fuel injection valve 6, and the required fuel amount GCYL is larger than the limit value of the in-cylinder injection amount. Sometimes, the injection mode setting means for setting the injection mode to the in-cylinder / port injection mode in which fuel is injected from both the in-cylinder fuel injection valve 6 and the port fuel injection valve 8 (ECU 2, steps 40 and 38 in FIG. 7). In-cylinder injection amount GCYLD # n injected from in-cylinder fuel injection valve 6 and port fuel injection according to required fuel amount GCYL and injection mode Injection amount calculating means for calculating a port injection amount GCYLP # n ejected from the valve 8, characterized in that it comprises, as (ECU 2, step 24 to 27 in FIG. 6).

  According to this fuel injection control device for an internal combustion engine, the limit value of the in-cylinder injection amount injected from the in-cylinder fuel injection valve is set according to the rotational speed of the internal combustion engine. The time that can be injected by the in-cylinder fuel injection valve, that is, the in-cylinder injection amount depends on the rotational speed of the internal combustion engine, and becomes shorter as the rotational speed is higher. Therefore, the limit value of the in-cylinder injection amount can be appropriately set according to the rotational speed of the internal combustion engine by the above setting.

  Further, in the present invention, when the required fuel amount calculated according to the rotational speed and load of the internal combustion engine is equal to or less than the limit value of the in-cylinder injection amount, the injection mode is set to the in-cylinder injection mode. Is injected only from the cylinder fuel injection valve. Therefore, in-cylinder injection can be performed as appropriately as possible within the limit set by the limit value as described above. Accordingly, the fuel filling rate can be improved, and the advantage of in-cylinder injection can be maximized, for example, knocking can be sufficiently suppressed by cooling the intake air by vaporizing the fuel.

  In addition, when the required fuel amount is larger than the limit value of the in-cylinder injection amount, fuel is injected from both the in-cylinder fuel injection valve and the port fuel injection valve by setting the injection mode to the in-cylinder / port injection mode. To do. Thereby, when the amount of fuel is insufficient only by in-cylinder injection, the shortage can be appropriately compensated by port injection by the port fuel injection valve.

  Furthermore, since the in-cylinder injection amount and the port injection amount are calculated according to the required fuel amount and the injection mode, the fuel amount required for the internal combustion engine can be supplied without excess or deficiency.

  According to a second aspect of the present invention, in the fuel injection control device 1 for the internal combustion engine 3 according to the first aspect, the injection amount calculation means calculates the port injection amount GCYLP # n as the port fuel injection in the in-cylinder / port injection mode. The valve 8 is set to a value larger than the minimum injection amount corresponding to the minimum injection time (step 25 in FIG. 6).

  According to this configuration, since the injection time larger than the minimum injection time is secured as the injection time of the port fuel injection valve in the in-cylinder / port injection mode, the calculated port injection amount can be reliably injected. it can.

  According to a third aspect of the present invention, in the fuel injection control device 1 for the internal combustion engine 3 according to the second aspect, the limit value of the in-cylinder injection amount is an upper limit value GCYLD_LMTH set in accordance with the rotational speed of the internal combustion engine 3. And a lower limit value GCYLD_LMTL that is smaller than the upper limit value GCYLD_LMTH by at least the minimum injection amount of the port fuel injection valve 8 so as to have a hysteresis region (FIG. 9), and the injection mode setting means sets the required fuel amount GCYL. Is greater than the upper limit value GCYLD_LMTH, the injection mode is set to the in-cylinder / port injection mode (step 38 in FIG. 7), and the injection amount calculation means performs the in-cylinder injection amount GCYLD in the in-cylinder / port injection mode. Set #n to a value below the lower limit value GCYLD_LMTL (maximum value CYLD_MAX of the in-cylinder injection amount) With a constant, a port injection amount GCYLP # n, (step 23 to 25 in FIG. 6) to the required fuel amount GCYL set to a value obtained by subtracting the in-cylinder injection amount GCYLD # n since it is characterized.

  According to this configuration, the limit value of the in-cylinder injection amount is set so as to have a hysteresis range from the upper limit value and the lower limit value, and the difference between the upper limit value and the lower limit value, that is, the width of the hysteresis range is It is set above the minimum injection amount of the fuel injection valve. In addition, when the required fuel amount is larger than the upper limit value, the injection mode is set to the in-cylinder / port injection mode, the in-cylinder injection amount at that time is set to a value less than the lower limit value, and the port injection amount is It is set to a value obtained by subtracting the in-cylinder injection amount from the required fuel amount. From the above relationship, the port injection amount in the in-cylinder / port injection mode is always larger than the width of the hysteresis region, that is, the minimum injection amount of the port fuel injection valve. Thereby, the injection time of the port fuel injection valve exceeding the minimum injection time can be ensured, and the set port injection amount can be reliably supplied. Further, since the required fuel amount is supplied without excess or deficiency in each injection mode, there is no torque step at the time of switching the injection mode, and a torque shock or the like can be suppressed. Furthermore, hunting in the injection mode can be prevented by maintaining the injection mode when the required fuel amount shifts to the hysteresis range.

  According to a fourth aspect of the present invention, in the fuel injection control device 1 for the internal combustion engine 3 according to the third aspect, the injection amount calculation means sets the in-cylinder injection amount GCYLD # n to a lower limit value in the in-cylinder / port injection mode. A value smaller than GCYLD_LMTL by at least the minimum injection amount of the port fuel injection valve 8 (maximum in-cylinder injection amount GCYLD_MAX) is set, and the port injection amount GCYLP # n is changed from the required fuel amount GCYL to the in-cylinder injection amount GCYLD #. The value is set to a value obtained by subtracting n (steps 23 to 25 in FIG. 6).

  According to this configuration, in the in-cylinder / port injection mode, the in-cylinder injection amount is set to a value that is smaller than the lower limit value by at least the minimum injection amount of the port fuel injection valve. Therefore, the port fuel injection valve that exceeds the minimum injection time even when the injection mode is maintained in the in-cylinder / port injection mode due to the shift of the required fuel amount from the region larger than the upper limit value to the hysteresis region Can be ensured, and the set port injection amount can be reliably supplied.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an internal combustion engine 3 to which a fuel injection control device 1 according to the present embodiment is applied. The internal combustion engine (hereinafter referred to as “engine”) 3 is, for example, an in-line four-cylinder four-cycle gasoline engine mounted on a vehicle (not shown).

  An intake pipe 4 and an exhaust pipe 5 are connected to a cylinder head 3c of the engine 3, and an in-cylinder fuel injection valve 6 and a spark plug 7 (see FIG. 2) face the combustion chamber 3d for each cylinder 3a. (Only one is shown). The in-cylinder fuel injection valve 6 injects fuel, which has been pressurized to a high pressure by a first fuel pump (not shown), in the vicinity of the spark plug 7 in the combustion chamber 3d. Further, the valve opening time and valve opening timing of the in-cylinder fuel injection valve 6 and the ignition timing of the spark plug 7 are controlled by an ECU 2 described later of the control device 1.

  The engine 3 is provided with a crank angle sensor 21. The crank angle sensor 21 includes a magnet rotor and an MRE pickup (both not shown), and outputs a CRK signal and a TDC signal (see FIG. 10), which are pulse signals, to the ECU 2 as the crankshaft 3e rotates. To do.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b is in a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke in any of the cylinders 3a. In the case of a cylinder, it is output every 180 ° crank angle.

  Further, the CRK signal and the TDC signal include a cylinder discrimination signal that is a pulse signal for discriminating the cylinder 3a at a predetermined crank angle position. The ECU 2 calculates the crank angle stage FISTG # n for fuel injection control for each cylinder 3a based on these three signals. This crank angle stage FISTG # n classifies a crank angle of 720 ° corresponding to one combustion cycle every 30 °, with a predetermined crank angle (for example, a crank angle generating a TDC signal) as a reference in each cylinder 3a. Stage numbers 0 to 23 are assigned in order. The subscript “#n” of FISTG # n indicates that the parameter is set for each cylinder 3a (n = 1 to 4), and this is the same for other applicable parameters. is there.

  A port fuel injection valve 8 is provided in the intake manifold of the intake pipe 4 so as to face the intake port 3f for each cylinder 3a. The port fuel injection valve 8 injects fuel boosted by a second fuel pump (not shown) into the intake port 3f. The valve opening time and timing of the port fuel injection valve 8 are controlled by the ECU 2.

  The intake pipe 4 is provided with a throttle valve mechanism 9. The throttle valve mechanism 9 has a rotatable throttle valve 9a disposed in the intake pipe 4 and a TH actuator 9b for driving the throttle valve 9a. The TH actuator 9b is a combination of a motor and a gear mechanism (both not shown), and is driven by a control signal from the ECU 2, whereby the opening of the throttle valve 9a is changed, whereby the intake air amount Is controlled.

  The ECU 2 further receives a detection signal indicating an accelerator pedal operation amount (hereinafter referred to as “accelerator opening”) AP from the accelerator opening sensor 22, and coolant water circulating in the main body of the engine 3 from the engine water temperature sensor 23. Detection signals representing temperature (hereinafter referred to as “engine water temperature”) TW are output.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The ECU 2 determines the operating state of the engine 3 according to the detection signals from the sensors 21 to 23 described above, and determines the combustion mode of the engine 3. Further, according to the determined combustion mode, fuel injection control for controlling the in-cylinder fuel injection valve 6 and the port fuel injection valve 8, and intake air amount control for controlling the throttle valve mechanism 9 are executed.

  In the present embodiment, the ECU 2 corresponds to a required fuel amount calculation unit, a limit value setting unit, an injection mode setting unit, and an injection amount calculation unit.

  The combustion mode is composed of the following stratified self-ignition combustion mode, stratified flame propagation combustion mode, and homogeneous flame propagation combustion mode.

(1) Stratified self-ignition combustion mode Combustion mode in which fuel is injected from the in-cylinder fuel injection valve 6 during the compression stroke to produce a stratified mixture and self-ignited combustion (2) Stratified flame propagation combustion mode Compression A combustion mode in which a stratified mixture is generated by injecting fuel from the in-cylinder fuel injection valve 6 during a stroke, and this is flame-propagated by spark ignition by the spark plug 7 (3) Homogeneous combustion mode A cylinder during the intake stroke A combustion mode in which a homogeneous air-fuel mixture is generated by injecting fuel from the internal fuel injection valve 6 and flame propagation combustion is performed by spark ignition. Further, in the case where the fuel amount is insufficient only by the in-cylinder injection by the in-cylinder fuel injection valve 6 with respect to the required fuel amount GCYL required for the engine 3, in order to compensate for this, the intake stroke is started from the end of the exhaust stroke. Then, port injection by the port fuel injection valve 8 is also executed.

  The combustion mode is determined as follows. First, the required torque PMCMD required for the engine 3 is calculated by searching a predetermined map (not shown) according to the engine speed NE and the accelerator pedal opening AP by the required torque calculation process of FIG. Step 1).

  Next, the combustion mode is determined according to the engine speed NE and the calculated required torque PMCMD by the combustion mode determination process of FIG. First, in step 11, it is determined by referring to the map of FIG. 5 whether or not the engine speed NE and the required torque PMCMD are in the first operating range corresponding to the low / medium speed / medium load range. When the determination result is YES, the combustion mode is determined to be the stratified self-ignition combustion mode, and the combustion mode value STS_BURNCMD is set to “1” (step 12).

  When the determination result in step 11 is NO, it is determined whether or not the engine speed NE and the required torque PMCMD are in the second operation range corresponding to the low / medium rotation / low load range (step 13). When the determination result is YES, the combustion mode is determined to be the stratified flame propagation combustion mode, and the combustion mode value STS_BURNCMD is set to “2” (step 14).

  When the determination result of step 13 is NO and the engine speed NE and the required torque PMCMD are in the third operation region other than the first and second operation regions, the combustion mode is determined to be the homogeneous flame propagation combustion mode, and the combustion mode The value STS_BURNCMD is set to “3” (step 15), and this process is terminated.

  Next, fuel injection control processing for the homogeneous combustion mode among the above combustion modes will be described with reference to FIG. This process is executed in synchronism with the generation of the CRK signal.

  First, in step 21, the required fuel amount GCYL required for each cylinder 3a of the engine 3 is calculated by searching a predetermined map (not shown) according to the engine speed NE and the required torque PMCMD.

  Next, limit processing of the in-cylinder injection amount GCYLD is executed (step 22). This limit process calculates the maximum value of the in-cylinder injection amount GCYLD, and the injection mode is an in-cylinder injection mode (hereinafter referred to as “DI mode”) in which only in-cylinder injection by the in-cylinder fuel injection valve 6 is executed. The in-cylinder / port injection mode (hereinafter referred to as “DI / PI mode”) in which in-cylinder injection and port injection by the port fuel injection valve 8 are used together is set for each cylinder 3a.

  FIG. 7 shows the subroutine. First, in step 31, by searching the map of FIG. 8 according to the engine speed NE and the engine water temperature TW, the upper limit value of the injection time of the in-cylinder fuel injection valve 6 (hereinafter referred to as “in-cylinder injection time”). TCYLD_LMTH is calculated. In this map, the upper limit value TCYLD_LMTH is set to a smaller value because the higher the engine speed NE, the shorter the time that can be injected by the in-cylinder fuel injection valve 6. Further, the upper limit value TCYLD_LMTH is set to a smaller value because the necessity of cooling the intake air by in-cylinder injection becomes lower as the engine water temperature TW is lower.

Next, using the calculated upper limit value TCYLD_LMTH, the lower limit value TCYLD_LMTL for the in-cylinder injection time is calculated by the following equation (1) (step 32).
TCYLD_LMTL
= TCYLD_LMTH-DTCYLD_LMT (1)
Here, DTCYLD_LMT is a predetermined hysteresis amount, and is set to a value slightly larger than the minimum injection time of the port fuel injection valve 8. As described above, the limit value of the in-cylinder injection time is set to have a predetermined hysteresis amount DTCYLD_LMT from the upper and lower limit values TCYLD_LMTH / L.

  Next, the upper limit value GCYLD_LMTH and the lower limit of the in-cylinder injection amount are searched for the upper limit value TCYLD_LMTH and the lower limit value TCYLD_LMTL of the in-cylinder injection time by searching a predetermined injection time-injection amount conversion table (not shown). The values are converted into values GCYLD_LMTL, respectively (steps 33 and 34).

Next, the maximum value TCYLD_MAX of the in-cylinder injection time is calculated by the following equation (2) (step 35).
TCYLD_MAX
= TCYLD_LMTL-DTCYLD_LMT (2)
Thus, the maximum value TCYLD_MAX of the in-cylinder injection time is set to a value obtained by further subtracting the hysteresis amount DTCYLD_LMT from the lower limit value TCYLD_LMTL.

  Next, the calculated maximum value TCYLD_MAX of the in-cylinder injection time is converted to the maximum value GCYLD_MAX of the in-cylinder injection amount by searching the injection time-injection amount conversion table (step 36).

  Next, it is determined whether or not the required fuel amount GCYL calculated in step 21 of FIG. 6 is larger than the upper limit value GCYLD_LMTH of the in-cylinder injection amount (step 37). When the determination result is YES and GCYL> GCYLD_LMTH, the fuel amount is insufficient with only the in-cylinder injection with respect to the required fuel amount GCYL. Therefore, the injection mode is set to the DI / PI mode and the port injection is executed together. As a matter of fact, the port injection execution flag F_DLMT is set to “1” (step 38).

  On the other hand, when the determination result of step 37 is NO, it is determined whether or not the required fuel amount GCYL is equal to or less than the lower limit value GCYLD_LMTL of the in-cylinder injection amount (step 39). When the determination result is YES and GCYL ≦ GCYLD_LMTL, the fuel amount is sufficient only by the in-cylinder injection with respect to the required fuel amount GCYL. Therefore, it is assumed that the injection mode is set to the DI mode and the port injection is not performed. The execution flag F_DLMT is set to “0” (step 40).

  Further, when the determination result of step 39 is NO and GCYLD_LMTL <GCYL ≦ GCYLD_LMTH, that is, when the required fuel amount GCYL is within the hysteresis range defined by the upper and lower limit values GCYLD_LMTH / L, the present process is ended as it is. That is, in this case, the port injection execution flag F_DLMT is maintained at the previous value, and the injection mode is not switched.

  In step 41 following step 38 or 40, the crank angle stage FISTG # n for each cylinder 3a is not less than a predetermined lower limit value PISETSDL (for example, 6) and not more than a predetermined upper limit value PISETSDH (for example, 17). Is determined. The crank angle section defined by these lower limit value PISETSDL and upper limit value PISETSDL corresponds to the end of the expansion stroke from the start of the compression stroke.

  If the determination result in step 41 is YES and the engine 3 is in the compression stroke or the expansion stroke, the port injection execution flag F_DLMT # n for each cylinder 3a is set to the port injection execution flag F_DLMT set in step 38 or 40. (Step 42), and this process is terminated. That is, in this case, if the port injection execution flag F_DLMT is switched between “0” and “1”, the port-by-cylinder port injection execution flag F_DLMT # n is also switched accordingly, and the injection is performed. Mode switching is allowed.

  On the other hand, if the determination result in step 41 is NO and the engine 3 is in the exhaust stroke or the intake stroke, the port-by-cylinder port injection execution flag F_DLMT # n is maintained at its previous value F_DLMT # nz (step 43), and this process is performed. finish. That is, in this case, even if the port injection execution flag F_DLMT is switched between “0” and “1”, the cylinder-specific port injection execution flag F_DLMT # n is not switched, and switching of the injection mode is prohibited. Is done.

  Returning to FIG. 6, in step 23 following the in-cylinder injection amount limit process in step 22 described above, it is determined whether or not the port-by-cylinder port injection execution flag F_DLMT # n is “1”. If the determination result is YES and the injection mode of the cylinder 3a is the DI / PI mode, the in-cylinder injection amount GCYLD # n is set to the maximum value GCYLD_MAX calculated in step 36 of FIG. 7 (step 24). Further, the port injection amount GCYLP # n is set to the difference (= GCYL−GCYLD_MAX) between the required fuel amount GCYL and the maximum value GCYLD_MAX (step 25), and this process is terminated.

  On the other hand, if the determination result in step 23 is NO and the injection mode of the cylinder 3a is the DI mode, the in-cylinder injection amount GCYLD # n is set to the required fuel amount GCYL (step 26). Further, the port injection amount GCYLP # n is set to a value 0 (step 27), and this process is terminated.

  Hereinafter, the operations obtained by the above-described fuel injection control will be collectively described with reference to FIG. First, the upper limit value TCYLD_LMTH of the in-cylinder injection time is calculated according to the engine speed NE and the engine water temperature TW (step 31), and a predetermined hysteresis amount is subtracted from the upper limit value TCYLD_LMTH sequentially from the DTCYLD_LMT. A lower limit value TCYLD_LMTL and a maximum value TCYLD_MAX are calculated (steps 32 and 35). Further, these three values are converted into an injection amount using an injection time-injection amount conversion table, and an upper limit value GCYLD_LMTH, a lower limit value GCYLD_LMTL, and a maximum value GCYLD_MAX are determined (steps 33 and 34). 36).

  Next, from the relationship between the required fuel amount GCYL and the above three parameters of the in-cylinder injection amount, the injection mode is set according to the following cases A to D, the in-cylinder injection amount GCYLD # n, and the port An injection amount GCYLP # n is calculated.

・ Case A (GCYL ≦ GCYLD_LMTL)
When the required fuel amount GCYL is equal to or lower than the lower limit value GCYLD_LMTL, the port injection execution flag F_DLMT is set to “0” (step 40), and the injection mode is set to the DI mode. Accordingly, the in-cylinder injection amount GCYLD # n is set to the required fuel amount GCYL (step 26), and the port injection amount GCYLP # n is set to the value 0 (step 27).

Case B (GCYL: Hysteresis range from case A)
When the required fuel amount GCYL increases from the above case A and shifts to the hysteresis range between the upper and lower limit values GCYLD_LMTH / L (step 39: NO), the injection mode is maintained in the DI mode. As a result, as in case A, the in-cylinder injection amount GCYLD # n is set to the required fuel amount GCYL, and the port injection amount GCYLP # n is set to the value 0. In this case, since the required fuel amount GCYL is smaller than the upper limit value GCYLD_LMTH, the required fuel amount GCYL can be supplied only by in-cylinder injection.

・ Case C (GCYL> GCYLD_LMTH)
When the required fuel amount GCYL further increases from the case B and exceeds the upper limit value GCYLD_LMTH, the port injection execution flag F_DLMT is set to “1” (step 38), and the injection mode is switched to the DI / PI mode. Accordingly, the in-cylinder injection amount GCYLD # n is set to the maximum value GCYLD_MAX (step 24), and the port injection amount GCYLP # n is a value obtained by subtracting the maximum value GCYLD_MAX from the required fuel amount GCYL (= GCYL-GCYLD_MAX). ) Is set (step 25).

  As is apparent from FIG. 9, the port injection amount GCYLP # n at this time is a value larger than twice the injection amount corresponding to the hysteresis amount DTCYLD_LMT of the port injection time. As described above, the hysteresis amount DTCYLD_LMT is set to a value slightly larger than the minimum injection time of the port fuel injection valve 8. From the above relationship, the port injection amount GCYLP # n is set as described above, so that the port injection time exceeding twice the minimum injection time of the port fuel injection valve 8 is secured. Therefore, the port injection amount valve GCYLP #N can be reliably supplied with a margin.

・ Case D (GCYL: Hysteresis range from case C)
When the required fuel amount GCYL decreases from the above case C and shifts to the hysteresis range between the upper and lower limit values GCYLD_LMTH / L, the injection mode is maintained in the DI / PI mode. As a result, as in the case C, the in-cylinder injection amount GCYLD # n is set to the maximum value GCYLD_MAX, and the port injection amount GCYLP # n is set to (GCYL-GCYLD_MAX). As shown in FIG. 9, in this case, since the port injection time exceeding the minimum injection time of the port fuel injection valve 8 is secured, the port injection amount valve GCYLP # n can be reliably supplied.

  As described above, according to the present embodiment, the upper and lower limit values GCYLD_LMTH / L of the in-cylinder injection amount are set according to the engine speed NE, and the required fuel amount GCYL is equal to or lower than the lower limit value GCYLD_LMTL. Since the injection mode is set to the DI mode, in-cylinder injection can be performed as appropriately as possible within the limit corresponding to the engine speed NE. Accordingly, the fuel filling rate can be improved, and the advantage of in-cylinder injection can be maximized, for example, knocking can be sufficiently suppressed by cooling the intake air by vaporizing the fuel.

  Further, when the required fuel amount GCYL is larger than the upper limit value GCYLD_LMTH of the in-cylinder injection amount, the injection mode is set to the DI / PI mode. It can be properly compensated by port injection. As described above, the required fuel amount GCYL required for the engine 3 can be supplied without excess or deficiency. Furthermore, since the injection mode is maintained when the required fuel amount GCYL is in the hysteresis range of the upper and lower limit values GCYLD_LMTH / L, hunting in the injection mode can be prevented.

  Further, the width of the hysteresis region is set to be equal to or greater than the minimum injection amount corresponding to the minimum injection time of the port fuel injection valve 8, and the maximum value GCYL_MAX of the in-cylinder injection amount is set to be further wider than the lower limit value GCYLD_LMTL. The maximum value GCYL_MAX is set as the in-cylinder injection amount GCYLD # n in the DI / PI mode. With this setting, the port injection amount GCYLP # n in the DI / PI mode is always larger than the minimum injection amount of the port fuel injection valve 8 even when the required fuel amount GCYL is in the hysteresis range. Thereby, the injection time of the port fuel injection valve 8 exceeding the minimum injection time can be secured, and therefore the set port injection amount GCYLP # n can be reliably supplied.

  As described above, since the required fuel amount GCYL can be supplied without excess or deficiency in both the DI mode and the DI / PI mode, there is no torque step when switching the injection mode, and torque shock and the like can be suppressed.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the engine speed NE and the engine water temperature TW are used as engine parameters when setting the upper limit value TCYLD_LMTH for the in-cylinder injection time. However, the engine speed NE is essential, and the engine water temperature TW In addition or alternatively, other suitable parameters may be used. Further, in the embodiment, after obtaining the upper and lower limit values and the maximum value of the in-cylinder injection time, these are converted into the in-cylinder injection amount limit value, etc., but without such conversion, the cylinder The limit value of the internal injection amount may be obtained directly.

  Further, the embodiment is an example in which the combustion mode of the internal combustion engine includes three combustion modes including the homogeneous combustion mode, and the present invention is applied to the homogeneous combustion mode, but the in-cylinder injection mode and the port injection mode are Of course, the present invention may be applied as long as the combustion mode is switched.

  The present embodiment is an example in which the present invention is applied to an engine for a vehicle. However, the present invention is not limited to this, and is used for a marine propulsion device such as an outboard motor having a crankshaft arranged in a vertical direction. The present invention may be applied to engines and other industrial internal combustion engines. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 is a diagram schematically showing an internal combustion engine to which a fuel injection control device according to an embodiment is applied. It is a block diagram of a fuel injection control device. It is a flowchart which shows a request torque calculation process. It is a flowchart which shows the determination process of a combustion mode. 5 is a map used in the process of FIG. It is a flowchart which shows the fuel-injection control process for homogeneous combustion modes. It is a flowchart which shows the subroutine of the limit process of in-cylinder injection amount. It is a map used by the process of FIG. It is a figure which shows the setting condition of various parameters and injection mode by fuel injection control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel-injection control apparatus 2 ECU (Required fuel amount calculation means, limit value setting means, injection mode setting means, injection amount calculation means)
3 Engine 3a Cylinder 3f Intake port 6 In-cylinder fuel injection valve 8 Port fuel injection valve 21 Crank angle sensor (rotational speed detection means)
22 Accelerator opening sensor (load detection means)
NE engine speed (speed of internal combustion engine)
AP accelerator opening (load of internal combustion engine)
GCYL Required fuel amount
GFPI Required port injection amount GCYLD_LMTH Upper limit value GCYLD_LMTL Lower limit value for in-cylinder injection amount GCYLD # n In-cylinder injection amount GCYLP # n Port injection amount

Claims (4)

A fuel injection control device for an internal combustion engine having an in-cylinder fuel injection valve for injecting fuel into a cylinder and a port fuel injection valve for injecting fuel into an intake port,
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Load detecting means for detecting a load of the internal combustion engine;
A required fuel amount calculating means for calculating a required fuel amount required for the internal combustion engine according to the detected rotational speed and load of the internal combustion engine;
Limit value setting means for setting a limit value of the in-cylinder injection amount injected from the in-cylinder fuel injection valve according to the rotational speed of the internal combustion engine;
When the calculated required fuel amount is less than or equal to the set in-cylinder injection amount limit value, the injection mode is set to an in-cylinder injection mode in which fuel is injected only from the in-cylinder fuel injection valve, and the request When the fuel amount is larger than the limit value of the in-cylinder injection amount, the injection mode is set to an in-cylinder / port injection mode in which fuel is injected from both the in-cylinder fuel injection valve and the port fuel injection valve. Injection mode setting means;
An injection amount calculating means for calculating an in-cylinder injection amount injected from the in-cylinder fuel injection valve and a port injection amount injected from the port fuel injection valve according to the required fuel amount and the injection mode;
A fuel injection control device for an internal combustion engine, comprising:   In the in-cylinder / port injection mode, the injection amount calculation means sets the port injection amount to a value larger than a minimum injection amount corresponding to a minimum injection time of the port fuel injection valve, The fuel injection control device for an internal combustion engine according to claim 1. The limit value of the in-cylinder injection amount is an upper limit value set according to the rotational speed of the internal combustion engine, and a lower limit value that is smaller than the upper limit value by at least the minimum injection amount of the port fuel injection valve. Is set to have a hysteresis range,
The injection mode setting means sets the injection mode to the in-cylinder / port injection mode when the required fuel amount is larger than the upper limit value,
The injection amount calculation means sets the in-cylinder injection amount to a value equal to or lower than the lower limit value in the in-cylinder / port injection mode, and changes the port injection amount from the required fuel amount to the in-cylinder injection amount. The fuel injection control device for an internal combustion engine according to claim 2, wherein the value is set to a value obtained by subtracting.   In the in-cylinder / port injection mode, the injection amount calculation means sets the in-cylinder injection amount to a value smaller than the lower limit value by at least the minimum injection amount of the port fuel injection valve, and the port The fuel injection control device for an internal combustion engine according to claim 3, wherein the injection amount is set to a value obtained by subtracting the in-cylinder injection amount from the required fuel amount.

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