JP5047011B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

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

  As a conventional fuel injection control device for this type of internal combustion engine, for example, the one disclosed in Patent Document 1 is known. In this internal combustion engine, in-cylinder injection is performed by the in-cylinder fuel injection valve at high rotation and high load, and port injection by the port fuel injection valve is performed at other times. The amount of fuel to be injected from the in-cylinder fuel injection valve and the port fuel injection valve is calculated according to the intake air amount and the rotational speed of the internal combustion engine. In this fuel injection control device, when the injection mode is switched from port injection to in-cylinder injection, the in-cylinder injection amount by the in-cylinder fuel injection valve is gradually increased while gradually decreasing the port injection amount by the port fuel injection valve. As a result, torque fluctuations during switching of the injection mode are suppressed.

  However, during the execution of the port injection and the in-cylinder injection, after the injected fuel adheres to the intake port or the wall surface in the cylinder, there is a so-called fuel transportation delay used for combustion in the next and subsequent combustion cycles. Arise. On the other hand, in the conventional fuel injection control device, the in-cylinder injection amount and the port injection amount are merely calculated according to the intake air amount and the rotation speed of the internal combustion engine, and the fuel transportation delay is not reflected. The amount of fuel actually used for combustion in the cylinder cannot be properly controlled. Such a problem becomes particularly prominent when the injection mode is switched from port injection to in-cylinder injection. That is, immediately after switching to in-cylinder injection, the fuel that has been injected from the port fuel injection valve and has adhered to the wall surface of the intake port is now taken away into the cylinder. Becomes higher. On the other hand, in the conventional fuel injection control device, since the injection amount by in-cylinder injection is only gradually increased while gradually reducing the injection amount by port injection, the amount of fuel supplied into the cylinder becomes excessive, The air-fuel ratio greatly fluctuates to the rich side, and thus the torque fluctuation also increases.

  The present invention has been made to solve such a problem, and when the injection mode is switched to the in-cylinder injection mode, the amount of fuel supplied into the cylinder can be reduced while favorably reflecting the behavior of the fuel. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can be controlled appropriately and thereby can stabilize the air-fuel ratio and suppress fluctuations in torque.

Japanese Patent Laying-Open No. 2005-220887

In order to achieve the above object, the invention according to claim 1 includes 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. The fuel injection control device 1 of the internal combustion engine 3 is operated by switching the mode between an in-cylinder injection mode in which fuel is injected from the in-cylinder fuel injection valve 6 and a port injection mode in which fuel is injected from the port fuel injection valve 8. Thus, when the injection mode is switched from the port injection mode to the in-cylinder injection mode, the in-cylinder attached fuel amount adhering to the wall surface in the cylinder 3a immediately after the switching (in the following embodiment, the same applies hereinafter) fuel quantity GWP) temporarily, is reset to 0, injected from in-cylinder fuel injection valve 6 after the, the fuel amount adhering to the wall surface of the cylinder 3a, the cylinder adhering fuel amount calculated as cylinder adherent fuel amount Calculation Stage (ECU 2, step 74 in FIG. 11, step 53 and 54 in FIG. 9) and, among the calculated cylinder adherent fuel amount, cylinder lifting away the amount of fuel carried off in the next combustion cycle (DI lifting left fuel In-cylinder carry fuel amount calculating means (ECU 2, step 43 in FIG. 8) for calculating the amount GWPCADI) and the port attached to the wall surface of the intake port 3f immediately before the switching when switching to the in-cylinder injection mode Of the attached fuel amount GWPP, a port carry fuel amount calculating means (ECU 2, step 44 in FIG. 8) for calculating a port carry fuel amount (switched carry fuel amount GWPCAP) taken into the cylinder 3a in the next combustion cycle. ) And operating state detecting means (a crank angle sensor 21, an accelerator) for detecting the operating state (engine speed NE, required torque PMCMD) of the internal combustion engine 3. An opening sensor 24), a required fuel amount calculating means (ECU 2, step 1 in FIG. 3) for calculating a required fuel amount GCYL to be supplied to the internal combustion engine 3 according to the detected operating state of the internal combustion engine 3. When switching to the in-cylinder injection mode, the in-cylinder to be injected from the in-cylinder fuel injection valve 6 according to the calculated in-cylinder carry-off fuel amount and the port carry-out fuel amount based on the calculated required fuel amount GCYL In-cylinder net injection amount determination means (ECU 2, step 6 in FIG. 3) for determining a net injection amount (DI net injection amount GCYLNEDI).

According to the fuel injection control device for an internal combustion engine, the injection mode includes an in-cylinder injection mode for injecting fuel from the in-cylinder fuel injection valve into the cylinder, and a port injection mode for injecting fuel from the port fuel injection valve to the intake port. Can be switched to. When the injection mode is switched from the port injection mode to the in-cylinder injection mode, immediately after the switching, once the cylinder adherent fuel amount adhering to the wall surface of the cylinder, is reset to 0, cylinder after its The amount of fuel injected from the fuel injection valve and attached to the wall surface in the cylinder is calculated as the in- cylinder attached fuel amount . Then, of the calculated in-cylinder attached fuel amount , the in-cylinder carried fuel amount to be taken away in the next combustion cycle is calculated, and the attached port fuel amount adhering to the wall surface of the intake port immediately before the switching is calculated. Of these, the amount of fuel carried away in the port in the next combustion cycle is calculated.

As described above, when the injection mode is switched to the in-cylinder injection mode, the in-cylinder fuel removal amount and the port removal fuel amount are calculated separately for the following reason. That is, it has been found that immediately after switching from the port injection mode to the in-cylinder injection mode, the removal rate of the fuel adhering to the wall surface of the intake port increases. The reason is that immediately after switching to the in-cylinder injection mode, the fuel that has been injected from the port fuel injection valve so far and has adhered to the wall surface of the intake port is brought into the cylinder exclusively. The fuel injected from the port fuel injection valve bounces on the wall surface of the intake port and remains without adhering to it other than the fuel that flows directly into the cylinder and the fuel that adheres to the wall surface of the intake port. This is because the fuel that remains in this way flows into the cylinder with a delay, so that the apparent removal amount increases. From this point of view, when switching to the in-cylinder injection mode, by calculating the in-cylinder carry fuel amount and the port carry fuel amount independently of each other, the cylinder corresponding to the difference in the take-off rate immediately after switching It is possible to appropriately calculate the amount of fuel carried away internally and the amount of fuel carried away by port.

  Further, according to the present invention, when the injection mode is switched to the in-cylinder injection mode, the in-cylinder removal calculated as described above based on the required fuel amount calculated according to the operating state of the internal combustion engine. The amount of fuel supplied into the cylinder can be determined while well reflecting the behavior of the fuel because the amount of fuel to be injected from the in-cylinder fuel injection valve is determined using the amount of fuel and the amount of fuel taken away from the port. It can be controlled appropriately. As a result, it is possible to stabilize the air-fuel ratio and suppress torque fluctuations.

  According to a second aspect of the present invention, in the fuel injection control apparatus 1 for the internal combustion engine 3 according to the first aspect, the in-cylinder carry-off fuel amount calculating means includes the in-cylinder attached fuel amount and the in-cylinder carry-out rate B) The in-cylinder carry fuel amount is calculated based on the product of B), and the port carry fuel amount calculation means calculates the port carry-out rate (port removal at mode switching) which is different from the port-attached fuel amount and the in-cylinder carry-out rate. The port removal fuel amount is calculated based on the product of the rate BP).

  According to this configuration, the in-cylinder removal rate and the port removal rate respectively used for calculating the in-cylinder removal fuel amount and the port removal fuel amount are set to different values. The port carry-out rate can be set to an appropriate value reflecting the degree of transportation delay according to the difference in the fuel attachment site. Thereby, the calculation accuracy of the in-cylinder carry fuel amount and the port carry-off fuel amount using them can be improved, and the in-cylinder net injection amount can be controlled more appropriately.

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, when the injection mode is other than when switching to the in-cylinder injection mode, the inside of the cylinder 3a and the wall surface of the intake port 3f Total carry-off fuel for calculating the total carry-off fuel amount (take-off fuel amount GWPCA) based on the product of the total stick-on fuel amount (attachment fuel amount GWP) adhering to the fuel and the total carry-out rate (take-off rate B) In-cylinder fuel injection in accordance with the calculated total carried-off fuel amount based on the required fuel amount GCYL at a time other than when the amount calculating means (ECU 2, step 42 in FIG. 8) and switching to the in-cylinder injection mode A total net injection amount calculating means (ECU 2, step 6 in FIG. 3) for calculating a total net injection amount (net injection amount GCYLNE) to be injected from the valve 6 or the port fuel injection valve 8, and a port carry-out rate Has a whole Wherein the Ri rate than is set to a large value.

  According to this configuration, the port removal rate is set to a value larger than the overall removal rate. This total removal rate represents the ratio of the fuel removed in the next combustion cycle out of the total amount of fuel attached to the cylinder and the wall surface of the intake port. In this way, by setting the port removal rate to a value larger than the overall removal rate, the port removal fuel amount is calculated to be a larger value, so the port removal fuel amount is placed on the wall surface of the intake port. In addition to the fuel adhering to the fuel, the fuel remaining in the intake port is taken into consideration, and the accuracy of calculating the amount of fuel taken away from the port can be further improved.

  According to a fourth aspect of the invention, in the fuel injection control device 1 for the internal combustion engine 3 according to the second or third aspect, the engine temperature detecting means (engine water temperature sensor 23) for detecting the temperature of the internal combustion engine 3 (engine water temperature TW). And a port removal rate calculating means (ECU 2, step 32 in FIG. 6) for calculating a port removal rate according to the detected engine temperature.

  In general, the degree to which the fuel adhering to the wall surface of the intake port is removed varies depending on the temperature of the internal combustion engine. The higher the temperature, the higher the temperature of the fuel and the higher the fluidity thereof, and thus the higher the temperature. Therefore, according to the present invention, the port removal rate can be appropriately calculated according to the temperature of the internal combustion engine, and the in-cylinder net injection amount can be optimally controlled using this port removal rate.

  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). Each cylinder 3a of the engine 3 is provided with a pair of intake valves 10 and 10 and a pair of exhaust valves 11 and 11 (only one is 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 fuel injection 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, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates.

  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. Based on these three signals, the ECU 2 calculates a crank angle stage FISTG for fuel injection control for each cylinder 3a. This crank angle stage FISTG classifies the 720 ° crank angle corresponding to one combustion cycle every 30 ° with respect to a predetermined crank angle (for example, a crank angle generating a TDC signal) in each cylinder 3a, and sequentially stages the cylinder 3a. Numbers 0 to 23 are assigned.

  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 amount of the throttle valve 9a is changed, whereby the intake air amount is reduced. Be controlled.

  Further, the intake pipe 4 is provided with an air flow meter 22 on the upstream side of the throttle valve mechanism 9. The air flow meter 22 outputs a detection signal representing the intake air amount QA to the ECU 2.

  A detection signal indicating the temperature TW (hereinafter referred to as “engine water temperature”) TW of the coolant circulating in the main body of the engine 3 is sent from the accelerator opening sensor 24 to the ECU 2 from the engine water temperature sensor 23. Detection signals representing AP (hereinafter referred to as “accelerator opening”) 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 operation state of the engine 3 according to the detection signals from the various sensors 21 to 24 described above, determines the injection mode, and controls the in-cylinder fuel injection valve 6 and the port fuel injection valve 8. Fuel injection control, intake air amount control for controlling the throttle valve mechanism 9 and the like are executed. The injection mode includes a first in-cylinder injection mode (hereinafter referred to as “first DI mode”) in which fuel is injected into the cylinder 3a from the in-cylinder fuel injection valve 6 during the intake stroke, and a in-cylinder fuel injection valve during the compression stroke. 6 includes a second in-cylinder injection mode for injecting fuel (hereinafter referred to as “second DI mode”) and a port injection mode for injecting fuel from the port fuel injection valve 8 to the intake port 3 f (hereinafter referred to as “PI mode”). And any one of these is determined. In the following description, the first DI mode and the second DI mode are collectively referred to as “DI mode” as appropriate.

  In the present embodiment, the ECU 2 includes an in-cylinder carry fuel amount calculation unit, a port carry fuel amount calculation unit, a required fuel amount calculation unit, an in-cylinder net injection amount determination unit, an overall carry fuel amount calculation unit, It corresponds to a net injection amount calculating means and a port removal rate calculating means.

  FIG. 3 is a flowchart showing a fuel injection control process executed by the ECU 2. This process is executed in synchronization with the generation of the TDC signal. Further, since this fuel injection control process is performed for each cylinder 3a based on the cylinder discrimination signal, the following description will be made for one cylinder 3a for convenience of explanation. First, in step 1 (illustrated as “S1”, the same applies hereinafter), a predetermined map (not shown) is searched according to the engine speed NE and the required torque PMCMD, so that each cylinder 3a of the engine 3 is requested. The required fuel amount GCYL is calculated. The required torque PMCMD is calculated by searching a predetermined map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  Next, in step 2, the direct rate A is calculated. This direct rate A is the amount of fuel injected from the in-cylinder fuel injection valve 6 or the port fuel injection valve 8 in the current combustion cycle, and the fuel burned in the combustion chamber 3d in the current combustion cycle of the fuel amount. Represents the proportion of quantity.

  FIG. 4 is a subroutine for calculating the direct rate A. In this process, first, in step 11, it is determined whether or not the start flag F_STMOD is “1”. The start flag F_STMOD is set to “1” when the engine 3 is cranking. When this determination result is YES, a direct map for cranking (hereinafter referred to as “direct ratio for cranking”) ACR is calculated by searching a predetermined map (not shown) according to the engine water temperature TW. (Step 12), then go to Step 13. On the other hand, if the determination result in step 11 is NO and the engine 3 is not cranking but is in normal operation, the process proceeds to step 13 as it is.

  In step 13, a direct map for PI mode (hereinafter referred to as “PI direct rate”) API is calculated by searching a predetermined map (not shown) according to the engine coolant temperature TW.

  Next, by searching respective predetermined maps (not shown) according to the engine coolant temperature TW, the direct rate for the first DI mode (hereinafter referred to as “first DI direct rate”) ADI1 and the second DI mode ADI2 (hereinafter referred to as “second DI direct rate”) ADI2 is calculated (steps 14 and 15).

Next, using these PI direct rate API, the first DI direct rate ADI1, and the second DI direct rate ADI2, the basic value ABASE of the direct rate is calculated according to the following equation (1) (step 16).
ABASE = KP × API + KD1 × ADI1 + KD2 × ADI2 (1)
Here, KP, KD1, and KD2 are coefficients, and are set according to the current injection mode. Specifically, when the injection mode is the PI mode, KP = 1 and KD1 = KD2 = 0 are set. In the first DI mode, KD1 = 1 and KP = KD2 = 0 are set. Further, in the second DI mode, KD2 = 1 and KP = KD1 = 0 are set. As described above, the calculated basic value ABASE corresponds to a direct rate corresponding to the currently set injection mode.

Next, the direct rate A is calculated according to the following equation (2) using the basic value ABASE and the direct rate for cranking ACR calculated in step 12 (step 17).
A = K1 * ACR + (1-K1) * ABASE (2)
Here, K1 is a predetermined smoothing coefficient (0 ≦ K1 ≦ 1.0), which is set to a maximum value (for example, 1.0) immediately after the start of cranking of the engine 3, and thereafter a minimum value (for example, 0).

  Next, limit processing is performed on the direct rate A calculated in step 17 (step 18), and then this processing is terminated. Specifically, when the calculated direct rate A exceeds the predetermined upper limit value, the direct rate A is set to the upper limit value, and when the calculated direct rate A is lower than the predetermined lower limit value, the direct rate A is set to the lower limit value. Set to.

  Returning to FIG. 3, in step 3 following step 2, the carry-out rate B is calculated. This removal rate B is attached to the attached fuel amount GWP attached to the wall surface in the cylinder 3a and the wall surface of the intake port 3f at the end of the previous combustion cycle when the injection mode is the DI mode or the PI mode. This represents the ratio of the amount of fuel taken away in the current combustion cycle in the fuel amount GWP. The wall surface in the cylinder 3a includes the top surface of the piston 3b in addition to the inner wall surface of the cylinder 3a.

  FIG. 5 is a subroutine for calculating the removal rate B. In this process, first, in step 21, it is determined whether or not the start flag F_STMOD is “1”. When the determination result is YES, by searching a predetermined map (not shown) according to the engine coolant temperature TW, a removal rate for cranking (hereinafter referred to as “cranking time removal rate”) BCR (Step 22), the process proceeds to step 23. If the determination result is NO, the process proceeds to step 23 as it is. The cranking removal rate BCR is set to a larger value as the engine water temperature TW is higher, and a PI removal rate BPI, a first DI removal rate BDI1, which will be described later, in all regions of the engine water temperature TW. The second DI removal rate BDI2 is set to a smaller value. This is because even if the engine water temperature TW is the same, the temperature of the cylinder 3a, the intake valve 10 and the exhaust valve 11 is often lower immediately after the start of cranking than in the normal operation. This is because the fluidity of the fuel is lowered by being deprived by them.

  In this step 23, the PI mode take-off rate (hereinafter referred to as “PI carry-out rate”) BPI is calculated by searching the map shown in FIG. 7 according to the engine coolant temperature TW. In this map, the PI removal rate BPI is set to a larger value as the engine coolant temperature TW is higher. This is because the higher the engine water temperature TW, the higher the temperature of the fuel adhering to the wall surface of the intake port 3f, and the higher the fluidity thereof, the more fuel is carried away.

  Next, by searching respective predetermined maps (not shown) according to the engine coolant temperature TW, the carry-out rate for the first DI mode (hereinafter referred to as “first DI carry-out rate”) BDI1, and the second DI The mode removal rate (hereinafter referred to as “second DI removal rate”) BDI2 is calculated (steps 24 and 25). In these maps, the first DI removal rate BDI1 and the second DI removal rate BDI2 are set to larger values as the engine water temperature TW is higher for the same reason as described in the PI removal rate BPI. In all regions of the engine water temperature TW, the PI removal rate BPI is set to a smaller value. This is because the injected fuel adheres to the wall surface of the intake port 3f in the PI mode, whereas the injected fuel adheres to the wall surface in the cylinder 3a in the DI mode. This is because the degree to which the spent fuel is taken away increases.

Next, using these PI removal rate BPI, first DI removal rate BDI1 and second DI removal rate BDI2, and the aforementioned coefficients KP, KD1 and KD2, the basic value BBASE of the removal rate according to the following equation (3): Is calculated (step 26).
BBASE = KP × BPI + KD1 × BDI1 + KD2 × BDI2 (3)
As described above, the calculated basic value BBASE is equivalent to the take-off rate corresponding to the currently set injection mode, like the direct rate basic value ABASE calculated by the equation (1).

Next, using this basic value BBASE and the cranking time removal rate BCR calculated in step 22 above, the removal rate B is calculated according to the following equation (4) (step 27), and this process ends.
B = K2 × BCR + (1-K2) × BBASE (4)
Here, K2 is a predetermined smoothing coefficient (0 ≦ K2 ≦ 1.0), and is set to a maximum value (for example, 1.0) immediately after the start of cranking of the engine 3, and then a minimum value (for example, for example) 0). For this reason, by setting the smoothing coefficient K2 for determining the weight of the take-off rate BCR for cranking as described above, the influence of the transport delay at the time of cranking is changed to the take-off rate B. It can be reflected to the maximum immediately after the start and thereafter can be gradually reflected, and the removal rate B is smoothly and appropriately transferred from the cranking removal rate BCR to the basic value BBASE. be able to.

  Returning to FIG. 3, in step 4 following step 3, a mode switching removal rate BP is calculated. This mode switching removal rate BP is the amount of fuel adhering to the port that has been injected from the port fuel injection valve 8 and adhered to the wall surface of the intake port 3f so far when the injection mode is switched from the PI mode to the DI mode. The ratio of the amount of fuel that flows into the cylinder 3a and is carried away in the current combustion cycle of the port-attached fuel amount GWPP with respect to the GWPP.

  FIG. 6 shows a subroutine for calculating the mode switching removal rate BP. In this process, in step 31, it is determined whether or not the switching flag F_PIDI is “1”. The switching flag F_PIDI is set to “1” during switching from the PI mode to the DI mode, and details thereof will be described later. When this determination result is NO, this process is terminated as it is.

  On the other hand, if the determination result in step 31 is YES and switching to the DI mode is in progress, the mode switching removal rate BP is calculated by searching the map shown in FIG. 32) The process is terminated. This mode switching removal rate BP is also set to a larger value as the engine water temperature TW is higher for the same reason as described in the PI removal rate BPI. Further, the mode switching removal rate BP is set to a value larger than the PI removal rate BPI in the entire region of the engine coolant temperature TW. This is because immediately after switching to the DI mode, the fuel that has been injected from the port fuel injection valve 8 and has adhered to the wall surface of the intake port 3f is brought into the cylinder 3a exclusively. Since the fuel that has been bounced at the wall surface of the intake port 3f remains without adhering to the wall and flows into the cylinder 3a with a delay, the apparent carry-out amount increases, and the degree to which the fuel is taken away This is because of the increase.

  Returning to FIG. 3, in step 5 following step 4, the carry-off fuel amount GWPCA is calculated. This carried-off fuel amount GWPCA is the amount of fuel burned in the current combustion cycle out of the fuel amount adhering to the cylinder 3a and the wall surface of the intake port 3f in the previous combustion cycle.

  FIG. 8 is a subroutine for the calculation process of the carried-off fuel amount GWPCA. In this process, first, in step 41, it is determined whether or not the switching flag F_PIDI is “1”. If this determination result is NO and switching to the DI mode is not being performed, the carry-off rate B calculated in step 27 is set to the attached fuel amount GWP adhered to the cylinder 3a or the wall surface of the intake port 3f in the previous combustion cycle. By multiplying (= B × GWP), a carry-off fuel amount GWPCA is calculated (step 42), and this process is terminated.

  On the other hand, when the determination result in step 41 is YES and the mode is switched to the DI mode, the fuel removal amount GWP adhered to the wall surface in the cylinder 3a by the DI mode is multiplied by the carry-off rate B (= GWP × B). To calculate the DI carry fuel amount GWPCADI (step 43). Next, the port removal fuel amount GWPP is calculated by multiplying the port attached fuel amount GWPP by the mode switching removal rate BP calculated in step 32 (= GWPP × BP) (step 44). Then, the carry-off fuel amount GWPCA is calculated from the sum of the DI carry-off fuel amount GWPCADI and the switching carry-off fuel amount GWPCAP (= GWPCADI + GWPCAP) (step 45), and this process is terminated.

  FIG. 9 is a subroutine for the calculation processing of the attached fuel amount GWP and the port attached fuel amount GWPP described above. In this process, first, in step 51, it is determined whether or not the fuel cut flag F_FC is “1”. When the determination result is YES and fuel cut for stopping the supply of fuel by the in-cylinder fuel injection valve 6 and the port fuel injection valve 8 is being executed, the injection adhered fuel amount GFW is set to 0 (step 52).

On the other hand, when the determination result in step 51 is NO, the injection adhered fuel amount GFW is calculated according to the following equation (5) using the direct rate A calculated in step 17 (step 53).
GFW = (1-A) × GCYLNEZ (5)
This injected attached fuel amount GFW is the amount of fuel attached to the wall surface in the cylinder 3a among the amount of fuel injected from the in-cylinder fuel injection valve 6 or the port fuel injection valve 8 in the current combustion cycle. Moreover, GCYLNEZ in the formula (5) is the previous value of the net injection amount.

Next, the attached fuel amount GWP is calculated according to the following equation (6) using the calculated injected attached fuel amount GFW and the carry-out rate B calculated in step 27 (step 54).
GWP = GFW + (1-B) × GWPZ (6)
Here, GWPZ in the second term is the previous value of the adhered fuel amount GWP, and therefore the entire second term is the amount of fuel adhering to the wall surface in the cylinder 3a at the end of the previous combustion cycle. . For this reason, the attached fuel amount GWP obtained by the equation (6) represents the total amount of fuel attached to the wall surface in the cylinder 3a at the end of the current combustion cycle.

  Next, it is determined whether or not the switching flag F_PIDI is “1” (step 55). If the determination result is NO and switching to the DI mode is not in progress, the port attached fuel amount GWPP is set to the value 0 (step 56), and this process is terminated.

On the other hand, when the determination result in step 55 is YES and the mode is switched to the DI mode, the port removal fuel amount GWPP is calculated according to the following equation (7) using the mode switching removal rate BP calculated in step 32. Calculation is made (step 57), and this process is terminated.
GWPP = (1-BP) × GWPPZ (7)
Here, GWPPZ is the previous value of the port attached fuel amount GWPP.

  Returning to FIG. 3, in step 6 following step 5, the fuel to be injected from the in-cylinder fuel injection valve 6 or the port fuel injection valve 8 according to the direct ratio A and the carried-off fuel amount GWPCA calculated as described above. The net injection amount GCYLNE, which is the amount, is calculated, and this process ends.

  FIG. 10 is a subroutine for the calculation process of the net injection amount GCYLNE. In this process, first, in step 61, it is determined whether or not the fuel cut flag F_FC is “1”. If the determination result is YES and the fuel cut is being executed, the net injection amount GCYLNE is set to 0 (step 62), and then the present process is terminated.

On the other hand, when the determination result in step 61 is NO, the required fuel amount GCYL, the direct rate A and the carry-off fuel amount GWPCA calculated in steps 1, 2, and 5 are used, and the net injection amount is calculated according to the following equation (8). A basic value GCYLNEB is calculated (step 63).
GCYLNEB = (GCYL-GWPCA) / A (8)

  Next, a net injection amount GCYLNE is calculated by searching a predetermined map (not shown) set for each injection mode in accordance with the basic value GCYLNEB (step 64), and the present process is terminated. Specifically, when the injection mode is the PI mode, the PI mode net injection amount (PI net injection amount) GCYLNEPI is calculated from the PI mode map. When the injection mode is the first DI mode, the first DI mode map is used. The 1DI net injection amount GCYLNEDI1 is calculated, and the second DI net injection amount GCYLNEDI2 is calculated from the map for the second DI mode in the second DI mode. Hereinafter, the first DI net injection amount GCYLNEDI1 and the second DI net injection amount GCYLNEDI2 will be collectively referred to as DI net injection amount GCYLNEDI as appropriate.

  FIG. 11 is a flowchart showing a switching determination process for determining whether or not switching to the DI mode is in progress. This process is executed for each cylinder 3a in synchronization with the generation of the CRK signal. In this process, first, in step 71, it is determined whether or not the crank angle stage FISTG of the cylinder 3a is not less than a predetermined lower limit value PISETSGL (for example, 6) and not more than a predetermined upper limit value PISETSGH (for example, 11). . The crank angle section defined by these lower limit value PISETSGL and upper limit value PISETSGH corresponds to the start to end of the compression stroke. When this determination result is NO, this process is terminated as it is.

  On the other hand, if the determination result in step 71 is YES and the cylinder 3a is in the compression stroke, it is determined whether or not the DI mode flag F_DIOK has changed from “0” to “1” between the previous time and this time (step 72). ). The DI mode flag F_DIOK is set to “1” during execution of the DI mode.

  If the determination result is YES and immediately after switching to the DI mode, the attached fuel amount GWP calculated in step 54 is set as the port attached fuel amount GWPP (step 73). Thereby, the port attached fuel amount GWPP is set to the total amount of fuel attached to the wall surface of the intake port 3f immediately before switching to the DI mode.

  Next, the attached fuel amount GWP is reset to 0 (step 74). As described above, the attached fuel amount GWP calculated in step 54 in the subsequent loop does not include the fuel attached to the wall surface of the intake port 3f, but includes only the fuel attached to the wall surface in the cylinder 3a in the DI mode. It is. Then, in order to indicate that switching to the DI mode is in progress, the switching flag F_PIDI is set to “1” (step 75), and this processing is terminated.

When the determination result of step 72 is NO, the determination result of step 76 becomes YES by executing this step 75. In this case, the port attached fuel amount GWPP calculated in step 57 is a predetermined threshold value. It is determined whether or not it is smaller than GREF (for example, 1.0 × 10 ⁻⁴ g) (step 77). When this determination result is NO, this process is terminated as it is.

  On the other hand, when the determination result in step 77 is YES and the port-attached fuel amount GWPP falls below the threshold value GREF, the fuel adhering to the wall surface of the intake port 3f almost no longer remains, and switching to the DI mode is performed. After determining that the process has been completed and resetting the switching flag F_PIDI to “0” (step 78), the present process is terminated.

  Hereinafter, the operations obtained by the above-described fuel injection control will be collectively described with reference to FIG. In this example, before the timing t1, the injection mode is set to the PI mode, and accordingly, the DI mode flag F_DIOK and the switching flag F_PIDI are both set to “0”. As a result, when the determination result in step 41 in FIG. 8 is NO, the product of the adhered fuel amount GWP calculated in step 54 and the removal rate B calculated in step 27 as the removed fuel amount GWPCA. Is used (step 42). Then, using this carry-off fuel amount GWPCA, a PI net injection amount GCYLNEPI injected from the port fuel injection valve 8 is calculated.

  When the execution condition of the DI mode is satisfied from this state, the DI mode flag F_DIOK is set to “1”, and the mode is switched to the DI mode (t1). As a result, the determination result in step 72 of FIG. 11 is YES, so that the attached fuel amount GWP so far is set as the port attached fuel amount GWPP (step 73). At this time, the attached fuel amount GWP is reset to the value 0, so that the attached fuel amount GWP calculated in the subsequent loops is injected from the in-cylinder fuel injection valve 6 and adheres to the wall surface in the cylinder 3a. It becomes the sum total of the amount of fuel that was done. Further, as the DI mode flag F_DIOK is switched to “1”, the switching flag F_PIDI is switched from “0” to “1”, and the determination result in step 41 becomes YES, whereby the carried-off fuel amount GWPCA is obtained. , DI removal fuel amount GWPCADI, which is the product of adhesion fuel amount GWP and removal rate B, and switching removal fuel amount GWPCAP, which is the product of port attachment fuel amount GWPP and mode change removal rate BP The sum is used (steps 43-45). Then, the DI net injection amount GCYLNEDI injected from the in-cylinder fuel injection valve 6 is calculated using the carry-off fuel amount GWPCA.

  Thereafter, when the port-attached fuel amount GWPP calculated in step 57 falls below the threshold value GREF (t2), almost no fuel has adhered to the wall surface of the intake port 3f immediately before switching to the DI mode. As a result, it is determined that the switching to the DI mode has been completed, and the switching flag F_PIDI is set to “0”. As a result, when the determination result in step 41 becomes NO again, the carried fuel amount GWPCA is calculated according to the adhered fuel amount GWP, not the port attached fuel amount GWPP.

  As described above, according to the present embodiment, when the injection mode is switched from the PI mode to the DI mode, the DI removed fuel amount GWPCADI and the switched removed fuel amount GWPCAP are calculated independently of each other. The DI removal fuel amount GWPCADI and the switching removal fuel amount GWPCAP commensurate with the difference between the leaving rate B and the mode switching removal rate BP can be calculated appropriately. Further, since the DI net injection amount GCYLNEDI is calculated using the DI carry-off fuel amount GWPCADI and the switching carry-off fuel amount GWPCAP, the fuel amount supplied into the cylinder 3a while favorably reflecting the behavior of the fuel. As a result, the air-fuel ratio can be stabilized and torque fluctuations can be suppressed.

  Furthermore, since the removal rate B and the mode switching removal rate BP are set to different values from each other, the removal rate B and the mode switching removal rate BP are set in accordance with the difference in the fuel adhesion site. It can be set to an appropriate value reflecting the degree of each transport delay.

  Further, since the mode switching removal rate BP is set to a value larger than the PI removal rate BPI, the switching removal fuel amount GWPCAP is added to the fuel adhering to the wall surface of the intake port 3f, The value also takes into account the fuel remaining in the intake port 3f, and the calculation accuracy of the switched carry-off fuel amount GWPCAP can be further improved.

  Furthermore, since the take-off rate B and the mode-switching take-off rate BP are appropriately calculated according to the engine water temperature TW, the net injection amount GCYLNE can be optimally controlled using them.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the mode switching time removal rate BP is calculated according to the engine water temperature TW, but instead of or together with this, other appropriate parameters representing the temperature of the engine 3, for example, It may be calculated according to the engine speed NE or the intake air amount QA. The same applies to the carry-out rate B and the direct rate A.

  Further, 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 fuel-injection control process. It is a subroutine which shows the calculation process of a direct rate. It is a subroutine which shows the calculation process of a removal rate. It is a subroutine which shows the calculation process of the removal rate for mode switching. 7 is a map used in the processing of FIGS. 5 and 6. It is a subroutine which shows the calculation process of the amount of fuel to take away. It is a subroutine which shows the calculation process of the adhesion fuel amount and the port adhesion fuel amount. It is a subroutine which shows the calculation process of net injection amount. It is a flowchart which shows the switching determination process which determines whether it is switching to DI mode. It is a timing chart of the operation example obtained by the process of FIG.

Explanation of symbols

1 Fuel injection control device 2 ECU (cylinder carry fuel amount calculation means, port carry fuel amount calculation means, required fuel amount calculation
Exit means, in-cylinder net injection amount determination means, total carried-off fuel amount calculation means, overall net
Injection amount calculating means and port removal rate calculating means)
3 Engine 3a Cylinder 3f Intake port 6 In-cylinder fuel injection valve 8 Port fuel injection valve 21 Crank angle sensor (operating state detection means)
23 Engine water temperature sensor (Engine temperature detection means)
24 Accelerator opening sensor (operating state detection means)
GCYL Required fuel amount GCYLNEDI DI Net injection amount (in-cylinder net injection amount)
GCYLNE Net injection amount (overall net injection amount)
GWP Adhered fuel amount (In-cylinder adhering fuel amount, Total adhering fuel amount)
GWPCADI DI carried fuel amount (cylinder carried fuel amount)
GWPCAP changeover carry fuel amount (port carry fuel amount)
GWPCA Amount of fuel removed (total amount of fuel removed)
GWPP port attached fuel amount
B carry-out rate (in-cylinder carry-out rate, overall carry-out rate)
BP mode switching removal rate (port removal rate)
NE engine speed (operating condition of internal combustion engine)
PMCMD required torque (operating condition of internal combustion engine)
TW engine water temperature (temperature of internal combustion engine)

Claims (4)

An in-cylinder fuel injection valve for injecting fuel into the cylinder; a port fuel injection valve for injecting fuel into the intake port; and an injection mode, an in-cylinder injection mode for injecting fuel from the in-cylinder fuel injection valve; A fuel injection control device for an internal combustion engine operated by switching to a port injection mode for injecting fuel from the port fuel injection valve,
When switching the injection mode to the in-cylinder injection mode from the port injection mode, immediately after the switching, once the cylinder adherent fuel amount adhering to the wall surface in the cylinder, is reset to zero, the after that injected from in-cylinder fuel injection valve, a fuel amount adhering to the wall surface in the cylinder, a cylinder attached fuel amount calculating means for calculating as the cylinder adhesion fuel amount,
Of the calculated in-cylinder attached fuel amount , in-cylinder carried fuel amount calculating means for calculating the in-cylinder removed fuel amount to be carried out in the next combustion cycle;
Of the amount of fuel attached to the wall of the intake port immediately before the switching to the in-cylinder injection mode, the amount of fuel removed from the port that is taken into the cylinder in the next combustion cycle. A port removal fuel amount calculating means for calculating;
An operating state detecting means for detecting an operating state of the internal combustion engine;
A required fuel amount calculating means for calculating a required fuel amount to be supplied to the internal combustion engine in accordance with the detected operating state of the internal combustion engine;
When switching to the in-cylinder injection mode, injection should be made from the in-cylinder fuel injection valve in accordance with the calculated in-cylinder carry fuel amount and port carry fuel amount based on the calculated required fuel amount. In-cylinder net injection amount determining means for determining the in-cylinder net injection amount;
A fuel injection control device for an internal combustion engine, comprising: The in-cylinder carry fuel amount calculating means calculates the in-cylinder carry fuel amount based on the product of the in-cylinder attached fuel amount and the in-cylinder carry-off rate,
The port removal fuel amount calculating means calculates the port removal fuel amount based on a product of the port attachment fuel amount and a port removal rate different from the in-cylinder removal rate. The fuel injection control device for an internal combustion engine according to claim 1. When the injection mode is other than when switching to the in-cylinder injection mode, based on the product of the total amount of fuel adhering to the inside of the cylinder and the wall surface of the intake port and the total removal rate, the total removed fuel An overall carried fuel amount calculating means for calculating the amount;
When not switching to the in-cylinder injection mode, injection should be performed from the in-cylinder fuel injection valve or the port fuel injection valve according to the calculated total removed fuel amount based on the required fuel amount A total net injection amount calculating means for calculating a total net injection amount;
The fuel injection control device for an internal combustion engine according to claim 2, wherein the port removal rate is set to a value larger than the overall removal rate. Engine temperature detecting means for detecting the temperature of the internal combustion engine;
The fuel injection control device for an internal combustion engine according to claim 2 or 3, further comprising: a port removal rate calculating unit that calculates the port removal rate according to the detected engine temperature. .

Images