JP2013209938A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an fuel injection control device of an internal combustion engine which even when a fuel injection amount requested for a direct injection type injector is corrected in an amount reduction fashion, can ensure a fuel injection amount requested for contributing to combustion improvement in each fuel injection from the direct injection type injector which is divided into the injection of a plurality of times for one combustion cycle of the internal combustion engine.SOLUTION: A fuel injection control device of an internal combustion engine performing fuel injection from a direct injection type injector a plurality of times per one combustion cycle of the internal combustion engine, sets the respective target fuel injection amounts Qd1-Qd3 for each fuel injection from the direct injection type injector to be requested values according to the engine operating condition, sets the required minimum fuel injection amount for each fuel injection, reduces the target fuel injection amount successively from the fuel injection of lower priority among the respective fuel injections when the requested fuel injection amount is corrected in an amount reduction fashion, and sets the respective target fuel injection amounts Qd1-Qd3 after the reduction not to be smaller than the respective necessary minimum fuel injection amounts Qd1min-Qd3min in the amount reduction.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine provided with a direct injection injector that injects fuel directly into at least a cylinder as an injector for fuel injection.

  Conventionally, this type of fuel injection control device is applied to an internal combustion engine including a direct injection injector that directly injects fuel into a cylinder of the internal combustion engine and a port injection injector that injects fuel toward an intake port. In addition, there is known a technique that corrects the fuel injection amount from the port injector by decreasing the purge amount when purging the fuel evaporative gas and introducing it into the intake system (see, for example, Patent Document 1). ).

  More specifically, a limit value is provided for the amount of decrease for purge correction of the port injection injector so that the fuel injection amount from the port injector is not decreased more than necessary when the purge process is executed. Further, when the amount of reduction is not sufficient only by the amount of reduction correction for the fuel injection amount from the port injector, the amount that cannot be corrected by the port injection side is corrected by the direct injection side. Thereby, the air-fuel ratio control can be improved.

  Further, in the fuel injection control device described in Patent Document 1, when performing fuel injection from a direct injection injector, first, a target fuel injection amount in the fuel injection is obtained. This target fuel injection amount is set based on the required fuel injection amount in the entire internal combustion engine and the fuel injection ratio of the direct injection port injector and the port injection injector for obtaining the required fuel injection amount. The required fuel injection amount and the injection ratio are obtained based on the engine operating state such as the engine speed and the engine load. Then, by driving the direct injection injector so as to obtain the target fuel injection amount, fuel injection from the direct injection injector is performed so that at least a part of the required fuel injection amount is obtained.

  By the way, in recent years, in a fuel injection control apparatus that can execute fuel injection from a direct injection injector, fuel required for fuel injection from the direct injection injector is divided into a plurality of times in one combustion cycle of an internal combustion engine. In addition, there has been proposed a system in which injection is performed from a direct injection injector. As such multiple times of fuel injection, for example, fuel injection in the compression stroke, fuel injection in the latter half of the intake stroke, and fuel injection in the first half of the intake stroke can be considered.

  The division of fuel injection in such a direct injection injector is performed by dividing the target fuel injection amount of the entire fuel injected from the direct injection injector into target fuel injection amounts for each fuel injection in accordance with a predetermined ratio, and then performing these target fuel injections. This is achieved by driving the direct injection injector to obtain the quantity.

  Here, among the fuel injections from the direct injection injector, each fuel injection in the compression stroke, the latter stage of the intake stroke and the first half of the intake stroke is realized as shown in the following [1] to [3]. Related to.

  [1] The fuel injection in the compression stroke has a feature that the injected fuel is easily collected around the spark plug by the airflow in the cylinder, etc., so that the fuel in the cylinder is well ignited and the combustion speed of the fuel is increased. Contributes to speed. [2] In the fuel injection in the latter half of the intake stroke, when the moving speed of the piston becomes slow and the generation of airflow in the cylinder due to the movement of the piston becomes weak, the airflow in the cylinder is strengthened by the injected fuel, and good fuel combustion Contributes to [3] In the fuel injection in the first half of the intake stroke, the injected fuel can be directly attached to the top of the piston. Therefore, the top of the piston is cooled by the latent heat of vaporization of the fuel, and hence knocking in the internal combustion engine. This contributes to suppressing the occurrence of

JP 2006-90152 A

  In order to achieve good engine operation in an internal combustion engine equipped with a direct injection injector as described above, the respective fuel injections in the compression stroke, the late intake stroke and the early intake stroke are performed from the direct injection injector, respectively. It is desirable to obtain the effects shown in the above [1] to [3] as much as possible. In other words, if the effects shown in [1] to [3] can be obtained in combination, combustion can be improved and the performance of the internal combustion engine can be maximized.

  The effects shown in [1] to [3] can be obtained only when a fuel injection amount of a predetermined amount or more is secured in each fuel injection.

  However, in the fuel injection control device as described above, when the purge process as described in Patent Document 1, for example, is executed and the total fuel injection amount required for the direct injection is reduced, the compression stroke and the intake stroke are corrected. Of the fuel injections in the second half and the first half of the intake stroke, the fuel injection quantity (hereinafter referred to as the required minimum fuel injection quantity) greater than a predetermined quantity required to obtain the effect of the fuel injection is not secured in any one of the fuel injections May occur.

  Such a malfunction occurs for the following reason. That is, depending on the operating state of the internal combustion engine, among the above-described multiple fuel injections, there are a fuel injection that requires a small fuel injection amount and a fuel injection that requires a relatively large fuel injection amount in contrast. Sometimes. In this case, for example, when the purge process is executed, it is preferable to preferentially reduce the fuel injection amount in the former fuel injection. However, in the above-described fuel injection control device, since priority is not provided for each fuel injection, when a reduction correction is applied to the fuel injection amount of the direct injection injector, there are few of the multiple fuel injections. The fuel injection amount in fuel injection sufficient with the fuel injection amount is not necessarily reduced preferentially. If the fuel injection amount in a fuel injection that requires a relatively large amount of fuel injection among a plurality of fuel injections is corrected to be reduced more than necessary, the fuel injection amount in the fuel injection becomes the required minimum fuel injection amount. It will fall below.

  As described above, in the fuel injection control device as described above, when the fuel injection amount of the direct injection injector is corrected by the purge process or the like, any of the multiple fuel injections from the direct injection injector will be performed. A situation may occur in which the fuel injection amount in such fuel injection is less than the required minimum fuel injection amount.

  Therefore, in the fuel injection control apparatus as described above, it is difficult to obtain all the effects shown in the above [1] to [3], and there is a problem that expected combustion improvement cannot be achieved.

  The present invention has been made to solve the above-described conventional problems. Even when the fuel injection amount required for the direct injection injector is subjected to a reduction correction, the present invention per engine cycle. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can secure a fuel injection amount necessary to contribute to combustion improvement in each fuel injection from a direct injection injector divided into a plurality of times.

  In order to achieve the above object, a fuel injection control device for an internal combustion engine according to the present invention includes: (1) a direct injection injector capable of performing multiple fuel injections into a cylinder of the internal combustion engine per combustion cycle of the internal combustion engine. A fuel injection control device for an internal combustion engine for injecting fuel from the direct injection injector so as to obtain at least a part of a required fuel injection amount required based on an engine operating state, wherein the fuel injection control device from the direct injection injector A target fuel injection amount for multiple fuel injections is set to a required value according to the engine operating state, and a minimum fuel injection amount is set for each of the multiple fuel injections from the direct injection injector, When the fuel injection amount required for the direct injection injector among the required fuel injection amounts is corrected to decrease, the plurality of times from the direct injection injector Among the fuel injections, the target fuel injection amount is reduced in order from the low priority fuel injection, and when the target fuel injection amount is reduced, the target fuel injection amount after the reduction is reduced from the plurality of direct injection injectors. The configuration is such that it does not fall below the required minimum fuel injection amount set for each fuel injection.

  With this configuration, the fuel injection control device for an internal combustion engine according to the present invention can perform a plurality of times from the direct injection injector when the fuel injection amount required for the direct injection is reduced among the required fuel injection amounts. Among the fuel injections, the target fuel injection amount is decreased in order from the fuel injection with the lowest priority. At this time, the target fuel injection amount after the reduction is made not to be lower than the necessary minimum fuel injection amount set for each of a plurality of fuel injections from the direct injection injector.

  Thus, for example, even when the fuel injection amount required for the direct injection injector is corrected to be reduced by purging or the like, for any one of the fuel injections from the direct injection injector, It is possible to prevent a situation in which the target fuel injection amount set in this way is less than the required minimum fuel injection amount. Therefore, at least the necessary minimum fuel injection amount can be ensured in each of the multiple fuel injections from the direct injection injector.

  As described above, the fuel injection control apparatus for an internal combustion engine according to the present invention can perform multiple times per combustion cycle of the internal combustion engine even when the fuel injection amount required for the direct injection injector is corrected for reduction. In each fuel injection from the divided direct injection injectors, it is possible to secure a fuel injection amount necessary for contributing to improvement in combustion.

  The engine operating state includes, for example, the engine rotational speed of the internal combustion engine and the engine load. The necessary minimum fuel injection amount is a fuel injection amount that is equal to or greater than a predetermined amount necessary to obtain each effect corresponding to each fuel injection from the direct injection injector.

  The fuel injection control device for an internal combustion engine according to the present invention is the fuel injection control device for an internal combustion engine according to the above (1), wherein (2) of the plurality of fuel injections from the direct injection injector, The fuel injection at the timing close to the ignition of the internal combustion engine has a higher priority.

  As described above, the fuel injection control device for an internal combustion engine according to the present invention increases the priority of the fuel injection at the timing close to the ignition of the internal combustion engine among a plurality of fuel injections from the direct injection injector. This is because, among the multiple fuel injections from the direct injection injector, the closer to the ignition timing of the internal combustion engine, the greater the influence of the ignition of the fuel due to the difference in the fuel injection amount. This is because the closer the ignition timing of the internal combustion engine is, the higher the priority is. Thereby, since the target fuel injection amount can be secured preferentially as the fuel injection has a greater influence on the fuel ignition, the combustion state of the internal combustion engine can be improved.

  The fuel injection control device for an internal combustion engine according to the present invention is the fuel injection control device for an internal combustion engine according to (1) or (2), wherein (3) the required minimum fuel injection amount is the direct injection injector. And a value that is set to a value that is larger than the minimum fuel injection amount that can be injected at a time and smaller than the required value that is set for each of the plurality of fuel injections from the direct injector.

  With this configuration, the fuel injection control device for an internal combustion engine according to the present invention has a minimum required fuel injection amount equal to or greater than a predetermined amount necessary to obtain each effect corresponding to each fuel injection from the direct injection injector. It can be. In addition, the above-described effects can be obtained without depending on the performance of the direct injection injector.

  The fuel injection control device for an internal combustion engine according to the present invention is the fuel injection control device for an internal combustion engine according to any one of (1) to (3), wherein (4) the required minimum fuel injection amount is determined by the internal combustion engine. It has a configuration in which the amount is increased as the driving state becomes higher.

  With this configuration, the fuel injection control device for an internal combustion engine according to the present invention can set an optimum required minimum fuel injection amount in accordance with the engine operating state of the internal combustion engine. For example, the required high output of the internal combustion engine can be ensured by increasing the fuel injection amount at the time of a high load that requires a high output for the internal combustion engine.

  The fuel injection control device for an internal combustion engine according to the present invention is the fuel injection control device for an internal combustion engine according to any one of (1) to (4), wherein (5) the plurality of times of fuel injection from the direct injection injector. A first fuel injection for injecting fuel in a compression stroke close to ignition of the internal combustion engine, a second fuel injection for injecting fuel in an intake stroke farther from the ignition than the first fuel injection, and the second The third fuel injection for injecting the fuel in the intake stroke far from the ignition is performed rather than the fuel injection.

  With this configuration, the fuel injection control device for an internal combustion engine according to the present invention performs the first fuel injection in the compression stroke, so that the injected fuel can be easily collected around the spark plug by the airflow in the cylinder and the like. The combustion speed of the fuel can be improved by making the ignition to the fuel good. Further, by performing the second fuel injection in the intake stroke farther from the ignition than the first fuel injection, for example, in the latter half of the intake stroke, the moving speed of the piston becomes slow, and the generation of airflow in the cylinder due to the movement of the piston is weakened. When the airflow in the cylinder is strengthened, good fuel combustion can be obtained. Further, by performing the third fuel injection in the intake stroke farther from the ignition than the second fuel injection, for example, in the first half of the intake stroke, the injected fuel can be directly attached to the piston top. As a result, the piston top can be cooled by the latent heat of vaporization of the fuel, and as a result, the occurrence of knocking in the internal combustion engine can be suppressed.

  The internal combustion engine fuel injection control apparatus according to the present invention is the internal combustion engine fuel injection control apparatus according to any one of (1) to (5), wherein (6) the internal combustion engine is connected to an intake port of the internal combustion engine. A port injection injector capable of injecting fuel toward the fuel injection unit, and a configuration in which, out of the required fuel injection amount, fuel that cannot be injected by the plurality of fuel injections from the direct injection injector is injected from the port injection injector. .

  With this configuration, in order to obtain the required fuel injection amount, the fuel injection control device for an internal combustion engine according to the present invention increases each fuel injection amount beyond the target fuel injection amount in a plurality of fuel injections from the direct injection injector. Therefore, they can suppress adverse effects on fuel combustion. In addition, by injecting fuel from the port injector, it is possible to achieve a suitable homogenization of the air-fuel mixture. Furthermore, the fuel injection control apparatus for an internal combustion engine according to the present invention can be applied to an internal combustion engine that employs a dual-type fuel injection system having two types of injectors, a direct injection injector and a port injection injector.

  According to the present invention, each fuel injection from the direct injection injector divided into a plurality of times per one combustion cycle of the internal combustion engine, even when the fuel injection amount required for the direct injection injector is reduced. It is possible to provide a fuel injection control device for an internal combustion engine that can secure a fuel injection amount necessary to contribute to improvement in combustion.

1 is a schematic configuration diagram of an internal combustion engine to which a fuel injection control device according to an embodiment of the present invention is applied. It is explanatory drawing which shows the fuel-injection aspect from a direct injection injector. It is a graph which shows the relationship between the fuel injection timing regarding the fuel injection in the compression stroke from a direct injection injector, and the fuel period of the fuel in a cylinder. It is a graph which shows the difference of the change tendency of the fuel consumption of an internal combustion engine with respect to the change of the engine load with and without the fuel injection in the compression stroke from a direct injection injector. It is a graph which shows the change of the amount of unburned fuel in a cylinder with respect to the change of the fuel injection timing in the direct injection injector in an intake stroke. It is a graph which shows the relationship between the fuel injection quantity in the fuel injection in the first half of the intake stroke from a direct injection injector, and a knock limit ignition timing. It is a graph which shows the difference in the change tendency of the knock limit ignition timing with respect to the change of the engine load with and without the fuel injection in the first half of the intake stroke from the direct injection injector. It is a flowchart which shows the setting procedure of the target fuel injection amount in each fuel injection from a direct injection injector, and the target fuel injection amount in the fuel injection from a port injection injector. It is a flowchart which shows the calculation procedure of a 1st fuel injection period. It is a graph which shows the change tendency of the 1st fuel injection period to change of engine speed and engine load. It is a flowchart which shows the calculation procedure of a 2nd fuel injection period. It is a graph which shows the change tendency of the 2nd fuel injection period with respect to the change of an engine speed and engine load. It is a flowchart which shows the calculation procedure of a 3rd fuel injection period. It is a flowchart following FIG. (A) is a graph which shows the change aspect of the last ignition timings E, F, I, J, and MBT with respect to the change of an engine load, (b) is a graph which shows the change of the fuel-injection aspect in an internal combustion engine. . It is a flowchart which shows the calculation procedure of an ignition timing command value. It is a flowchart which shows the procedure of the reduction | decrease correction | amendment of the target fuel injection quantity in each fuel injection from a direct injection injector. It is explanatory drawing which shows the target fuel injection amount in each fuel injection from a direct injection injector, the required minimum fuel injection amount, and the amount of reductions.

  Hereinafter, a fuel injection control apparatus according to an embodiment of the present invention will be described with reference to FIGS. In the present embodiment, an example in which the fuel injection control device is applied to an internal combustion engine mounted on an automobile or the like will be described.

  In the present embodiment, the internal combustion engine 1 performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while a piston 13 described later reciprocates twice in a cylinder 40 as a cylinder. A description will be given assuming that the engine is constituted by a four-cycle gasoline engine that performs ignition during the compression stroke and the expansion stroke.

  As shown in FIG. 1, the intake passage 2 of the internal combustion engine 1 is provided with a throttle valve 4 that opens and closes to adjust the amount of air taken into the combustion chamber 3 (intake air amount). The opening degree of the throttle valve 4 (throttle opening degree) is adjusted according to the operation amount (accelerator operation amount) of the accelerator pedal 5 that is depressed by the driver. The internal combustion engine 1 also injects fuel into the combustion chamber 3 formed by the port injection injector 6 that injects fuel from the intake passage 2 toward the intake port 2 a of the combustion chamber 3, and the cylinder 40 and the piston 13. And a direct injection injector 7. The fuel stored in the fuel tank 8 is supplied to the injectors 6 and 7.

  That is, the fuel in the fuel tank 8 is pumped up by the feed pump 9 and then supplied to the port injector 6 via the low-pressure fuel pipe 31. The pressure of the fuel in the low-pressure fuel pipe 31 is adjusted to the feed pressure through the drive control of the feed pump 9 and is not excessively raised by the pressure regulator 32 provided in the low-pressure fuel pipe 31. Further, a part of the fuel in the low-pressure fuel pipe 31 pumped up by the feed pump 9 is pressurized to a pressure higher than the above-mentioned feed pressure (hereinafter referred to as direct injection pressure) by the high-pressure fuel pump 10 and then the high-pressure fuel. It is supplied to the direct injection injector 7 through the pipe 33.

  In the internal combustion engine 1, an air-fuel mixture consisting of fuel injected from the injectors 6 and 7 and air flowing through the intake passage 2 is filled in the combustion chamber 3, and the air-fuel mixture is ignited by a spark plug 12. When the air-fuel mixture after ignition burns, the piston 13 reciprocates due to the combustion energy at that time, and the crankshaft 14 rotates accordingly. On the other hand, the air-fuel mixture after combustion is sent out to the exhaust passage 15 as exhaust gas. Note that the combustion chamber 3 and the intake passage 2 are communicated and blocked by an intake valve 26 that opens and closes as the intake camshaft 25 that receives rotation transmission from the crankshaft 14 rotates. Further, the combustion chamber 3 and the exhaust passage 15 are communicated and blocked by an exhaust valve 28 that opens and closes as the exhaust camshaft 27 that receives the rotation transmission from the crankshaft 14 rotates.

  In the internal combustion engine 1, a variable valve timing mechanism 29 that changes the relative rotation phase of the intake camshaft 25 with respect to the crankshaft 14 (valve timing of the intake valve 26) as a variable valve mechanism that varies the opening / closing characteristics of the intake valve 26. Is provided. By driving the variable valve timing mechanism 29, both the valve opening timing and the valve closing timing of the intake valve 26 are advanced or retarded while the valve opening period (operating angle) of the intake valve 26 is kept constant.

  A canister 50, which is a collection container that collects fuel evaporative gas generated in the fuel tank 8, is connected to the fuel tank 8 via a vapor passage 51. The canister 50 is filled with a known adsorbent such as activated carbon that adsorbs the fuel evaporative gas. Further, the canister 50 is provided with an air passage 52 for introducing air into the canister 50 through a check valve during purging. The canister 50 is connected to a purge passage 53 for supplying the collected fuel evaporative gas to the intake passage 2 of the internal combustion engine 1.

  The purge passage 53 communicates with a purge port 54 that is opened on the downstream side of the throttle valve 4 in the intake passage 2. The purge passage 53 is provided with a purge control valve 55 that controls the purge amount.

  The opening degree of the purge control valve 55 is duty-controlled by an electronic control device 16 described later. As a result, the amount of fuel evaporative gas purged in the canister 50 and the amount of fuel introduced into the internal combustion engine 1 (hereinafter referred to as purge fuel amount) are controlled. The correction value for the purge fuel amount is the purge correction amount fpg. The electronic control unit 16 reduces the required fuel injection amount Qfin, which will be described later, by the purge correction amount fpg during the purge process.

  Next, the electrical configuration of the electronic control device 16 according to the present embodiment will be described.

  The electronic control device 16 controls various operations of the internal combustion engine 1. The electronic control unit 16 includes a CPU that executes various arithmetic processes related to the above control, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores CPU calculation results, and the like. Input / output ports for inputting / outputting signals are provided. The electronic control device 16 in the present embodiment constitutes a fuel injection control device according to the present invention.

  The input port of the electronic control unit 16 includes an accelerator position sensor 17, a throttle position sensor 18, an air flow meter 19, a crank position sensor 20, a cam position sensor 21, a water temperature sensor 22, a first pressure sensor 23, a second pressure sensor 24, and Various sensors such as knock sensor 30 are connected.

  The accelerator position sensor 17 detects an accelerator operation amount. The throttle position sensor 18 detects the throttle opening. The air flow meter 19 detects the amount of air passing through the intake passage 2 (intake air amount of the internal combustion engine 1). The crank position sensor 20 outputs a signal corresponding to the rotation of the crankshaft 14. The cam position sensor 21 outputs a signal corresponding to the rotational position based on the rotation of the intake camshaft 25. The water temperature sensor 22 detects the temperature of cooling water of the internal combustion engine 1 (hereinafter simply referred to as engine water temperature). The first pressure sensor 23 detects the fuel pressure (feed pressure) in the low-pressure fuel pipe 31. The second pressure sensor 24 detects the fuel pressure (direct injection pressure) in the high-pressure fuel pipe 33. Knock sensor 30 detects the occurrence of knocking in internal combustion engine 1.

  The output port of the electronic control unit 16 is connected to drive circuits of various devices such as the throttle valve 4, the port injection injector 6, the direct injection injector 7, the spark plug 12, and the valve timing variable mechanism 29.

  The electronic control unit 16 grasps the engine operation state such as the engine rotation speed and the engine load based on the signals input from the various sensors and the like, and based on the grasped engine operation state, the throttle valve 4, the injectors 6 and 7, the feed Command signals are output to drive circuits of various devices such as the pump 9, the spark plug 12 and the valve timing variable mechanism 29. In this way, various operation controls of the internal combustion engine 1 such as throttle opening control, fuel injection control, ignition timing control and intake valve 26 valve timing control of the internal combustion engine 1 are performed through the electronic control device 16.

  Incidentally, the engine rotation speed is obtained based on a detection signal from the crank position sensor 20. The engine load is calculated from a parameter corresponding to the intake air amount of the internal combustion engine 1 and the engine speed. The parameters corresponding to the intake air amount include the actual value of the intake air amount of the internal combustion engine 1 obtained based on the detection signal from the air flow meter 19, the throttle opening degree obtained from the detection signal from the throttle position sensor 18, and The accelerator operation amount etc. calculated | required based on the detection signal from the accelerator position sensor 17 are mentioned.

  The fuel injection amount control performed as one of the fuel injection controls of the internal combustion engine 1 obtains the required fuel injection amount Qfin for the internal combustion engine 1 as a whole based on the engine operating state such as the engine speed and the engine load, and the required fuel injection. This is realized by performing fuel injection from the port injector 6 and the direct injector 7 so as to obtain the amount Qfin. At this time, the electronic control unit 16 drives the direct injection injector 7 to inject fuel from the direct injection injector 7 so that at least a part of the required fuel injection amount Qfin obtained based on the engine operating state is obtained. Is supposed to do. In the present embodiment, as will be described later, the direct injection injector 7 can inject fuel into the cylinder 40 of the internal combustion engine 1 a plurality of times per one combustion cycle of the internal combustion engine 1.

  The multiple fuel injections from the direct injection injector 7 include fuel injection in the compression stroke (first fuel injection) in the internal combustion engine 1, fuel injection in the latter half of the intake stroke (second fuel injection), and the first half of the intake stroke. It is conceivable to perform fuel injection (third fuel injection). An example of the fuel injection period in each of these fuel injections is shown in FIG. In the first fuel injection period d1 shown in the figure, fuel injection is performed in the compression stroke. Further, in the second fuel injection period d2, fuel injection is performed in the latter half of the intake stroke, and in the third fuel injection period d3, fuel injection is performed in the first half of the intake stroke. With regard to the first fuel injection period d1, the second fuel injection period d2, and the third fuel injection period d3, the maximum determined based on such a predetermined interval or the like because of a relationship that requires a predetermined interval therebetween. A value exists.

  Here, in the present embodiment, a priority is set for each of the above-described fuel injections, and each target fuel in which at least a part of the requested fuel injection amount Qfin is set for each fuel injection in accordance with this priority. Assigned to the injection amount. When fuel injection from the port injector 6 is not performed, all of the required fuel injection amount Qfin is assigned to each target fuel injection amount set for each fuel injection from the direct injection injector 7. In the present embodiment, among the plurality of fuel injections, the higher the priority is given to the fuel injection at a timing close to the ignition (ignition timing) of the internal combustion engine 1. That is, the priority is increased in the order of fuel injection in the compression stroke, fuel injection in the latter half of the intake stroke, and fuel injection in the first half of the intake stroke. Such priority is set because it is considered that the influence of ignition on the fuel due to the difference in the fuel injection amount becomes larger as the fuel injection is closer to the ignition timing of the internal combustion engine 1.

  The fuel injection in the compression stroke from the direct injection injector 7, the fuel injection in the latter half of the intake stroke, and the fuel injection in the first half of the intake stroke are respectively described in the following [1] to [1] to As shown in [3], it relates to the realization of good engine operation.

  [1] The fuel injection in the compression stroke has a feature that the injected fuel is easily collected around the spark plug 12 by the air flow in the cylinder 40 and the like. Contributes to increasing the burning rate. Here, the relationship between the fuel injection timing in the direct injection injector 7 and the combustion period of the fuel in the cylinder 40 is shown in FIG. From this figure, when the fuel injection timing comes after the timing BDC (compression stroke), the combustion speed of the fuel in the cylinder 40 becomes faster and the combustion period of the fuel becomes shorter than before the timing BDC (intake stroke). I understand that FIG. 4 shows the difference in the change in fuel consumption of the internal combustion engine 1 with respect to the change in engine load when the fuel is injected from the direct injection injector 7 during the compression stroke. From the comparison between when there is fuel injection in the compression stroke from the direct injection injector 7 in this figure (solid line) and when there is no fuel injection (broken line), the operating range of the internal combustion engine 1 is increased by performing fuel injection in the compression stroke. It can be seen that when it is in the region near the load, the combustion speed of the fuel in the cylinder 40 is increased and the fuel efficiency of the internal combustion engine 1 is improved.

  [2] The fuel injection in the latter stage of the intake stroke is good when the moving speed of the piston 13 becomes slow and the generation of the airflow in the cylinder 40 due to the movement of the piston 13 becomes weak, and the airflow in the cylinder 40 is strengthened by the injected fuel. Contributes to obtaining a good fuel combustion. Here, the change in the amount of unburned fuel in the cylinder 40 with respect to the change in the fuel injection timing in the direct injection injector 7 in the intake stroke is shown in FIG. From this figure, if the air flow in the cylinder 40 is strengthened by the fuel injection in the latter stage of the intake stroke, the mixing of the fuel and air in the cylinder 40 is promoted and the fuel is burned well. It can be seen that the amount of unburned fuel within 40 decreases.

  [3] In the fuel injection in the first half of the intake stroke, the injected fuel can be directly attached to the top of the piston 13, so that the top of the piston 13 is cooled by the latent heat of vaporization of the fuel, and hence the internal combustion This contributes to suppressing the occurrence of knocking in the engine 1. Here, the fuel injection amount in the fuel injection in the first half of the intake stroke from the direct injection injector 7 and the ignition timing when the ignition timing of the internal combustion engine 1 is advanced to a limit at which knocking does not occur (knock limit ignition timing) FIG. 6 shows the relationship. From this figure, it can be seen that as the fuel injection amount in the first half of the intake stroke is increased, the top of the piston 13 is effectively cooled, and the knock limit ignition timing is thereby advanced. FIG. 7 shows the difference in the tendency of the change in the knock limit ignition timing with respect to the change in the engine load when the fuel injection from the direct injection injector 7 is in the first half of the intake stroke and when it is not. From the comparison of the knock limit ignition timing (solid line) when there is fuel injection in the first half of the intake stroke from the direct injection injector 7 in this figure and the knock limit ignition timing (two-dot chain line) when there is no fuel injection in the first half of the intake stroke, It can be seen that the knock limit ignition timing can be advanced by performing fuel injection. In this way, by advancing the knock limit ignition timing, the knock limit ignition timing can maximize the output torque in the internal combustion engine 1 when the operating range of the internal combustion engine 1 is in a region close to a high load. The ignition timing (MBT) is approached. This MBT is indicated by a broken line in the figure.

  Next, the operation of the electronic control device 16 according to the present embodiment will be described.

  In the electronic control unit 16, when the fuel is injected from the direct injection injector 7 and the port injection injector 6 so as to obtain the required fuel injection amount Qfin in the internal combustion engine 1, the direct injection injector 7 and the port injection injector 6 are driven as follows. Is done.

  That is, the target fuel injection amounts Qd1 to Qd3 relating to fuel injection in the compression stroke from the direct injection injector 7, the latter half of the intake stroke, and the first half of the intake stroke are set to required values according to the engine operating state. Specifically, among the fuel injection in the compression stroke, the fuel injection in the latter half of the intake stroke, and the fuel injection in the first half of the intake stroke in the direct injection injector 7, the target fuel injection amounts Qd1 to Qd1 Qd3 is set to a required value according to the engine operating state. By continuing the setting of the target fuel injection amount, the total value of the target fuel injection amounts can be brought close to the required fuel injection amount Qfin. Such setting of the target fuel injection amount is continued until the total value of the target fuel injection amounts becomes the required fuel injection amount Qfin.

  Then, the direct injection injector 7 is driven based on the target fuel injection amounts Qd1 to Qd3 so as to obtain the target fuel injection amounts Qd1 to Qd3 for the respective fuel injections set as described above.

  In this case, among the fuel injections from the direct injection injector 7, the target fuel injection amounts Qd <b> 1 to Qd <b> 3 in the same fuel injection are possible in order from the fuel injection having the highest priority under the engine operating state at that time. It is possible to set the value based on the engine operating state so that the value (required value) can be obtained as long as the fuel injection is effective. By driving the direct injection injector 7 so as to obtain the target fuel injection amounts Qd1 to Qd3 for each fuel injection set in this way, the respective effects of the fuel injections can be obtained as much as possible. , Which can maximize engine performance.

  Incidentally, the total value of the target fuel injection amounts Qd1 to Qd3 relating to the fuel injection in the compression stroke from the direct injection injector 7, the fuel injection in the latter half of the intake stroke, and the fuel injection in the first half of the intake stroke is the required fuel injection amount Qfin. It may be less than In this case, fuel corresponding to the required fuel injection amount Qfin cannot be injected by the fuel injection in the compression stroke from the direct injection injector 7, the fuel injection in the latter half of the intake stroke, and the fuel injection in the first half of the intake stroke. However, at this time, of the fuel for the required fuel injection amount Qfin, the amount of fuel that cannot be injected by each fuel injection from the direct injection injector 7 is the target fuel injection amount Qp in the fuel injection from the port injector 6. Set to Then, the port injector 6 is driven based on the target fuel injection amount Qp so as to obtain the target fuel injection amount Qp set in this way.

  Here, in each fuel injection from the direct injection injector 7, if the fuel injection amount is excessively increased beyond the target fuel injection amounts Qd1 to Qd3, the fuel combustion may be adversely affected.

  Taking this into consideration, the fuel for the required fuel injection amount Qfin can be injected by the fuel injection from the direct injection injector 7 in the compression stroke, the fuel injection in the latter half of the intake stroke, and the fuel injection in the first half of the intake stroke. Insufficient fuel is injected by fuel injection from the port injector 6. For this reason, in order to obtain the required fuel injection amount Qfin, each fuel injection amount from the direct injector 7 in each period increases beyond the respective target fuel injection amount, which adversely affects fuel combustion. Can be suppressed. In addition, by injecting fuel from the port injector 6, it is possible to achieve a suitable homogenization of the air-fuel mixture.

  Here, the effects shown in [1] to [3] described above are not obtained until a fuel injection amount (hereinafter referred to as “required minimum fuel injection amount”) of a predetermined amount or more is secured in each fuel injection from the direct injection injector 7. It is done. However, when the required fuel injection amount Qfin is corrected to be reduced by the purge process described above, the target fuel injection amount required for the direct injection injector 7 (target fuel injection amounts Qd1 to Qd3 set for each of a plurality of fuel injections). (Total value) is also corrected for reduction. For this reason, the target fuel injection amount in any one of the fuel injections from the direct injection injector 7 may be lower than the minimum required fuel injection amount.

  Therefore, in the present embodiment, the minimum required fuel injection amount is set for each fuel injection from the direct injection injector 7. Specifically, the electronic control unit 16 sets each necessary minimum fuel injection amount based on the engine speed, engine load, and engine water temperature of the internal combustion engine 1.

  For example, the required minimum fuel injection amount Qd3min in the first half of the intake stroke is increased as the internal combustion engine 1 enters a higher rotation / high load state. This is because the need for cooling in the cylinder 40 increases as the engine speed and the engine load increase. Further, the required minimum fuel injection amount Qd3min is reduced as the engine water temperature is lower. This is because when the engine water temperature is low, the necessity for cooling in the cylinder 40 is relatively reduced. Note that the above-described reduction includes the case where the required minimum fuel injection amount Qd3min becomes zero. Thus, in the present embodiment, it is possible to set the optimum required minimum fuel injection amount Qd3min according to the engine speed, the engine load, and the engine water temperature. For example, the required high output of the internal combustion engine 1 can be ensured by increasing the required minimum fuel injection amount Qd3min at the time of a high load where a high output is required for the internal combustion engine 1.

  Further, the required minimum fuel injection amount Qd2min in the latter half of the intake stroke is reduced as the engine water temperature is lower. This is because when the engine water temperature is low, fuel may not be vaporized and may be diluted with fuel and mixed with lubricating oil, so that the fuel injection amount in the fuel injection is reduced to suppress fuel dilution.

  In particular, in the present embodiment, the target fuel injection amount Qd3 in the fuel injection in the first half of the intake stroke with the lowest priority is the minimum fuel required as compared with other fuel injections (fuel injection in the compression stroke and the second half of the intake stroke). Since there is a high possibility that the injection amount will not be reached, the required minimum fuel injection amount Qd3min is used as a reference for setting each required minimum fuel injection amount. On the other hand, the target fuel injection amount Qd1 in the fuel injection in the compression stroke is compared with other fuel injections (fuel injection in the late intake stroke or the previous intake stroke) even if the required minimum fuel injection amount Qd1min is small. Since the priority is high, the amount of weight reduction is finally corrected. For this reason, it is possible to secure the target fuel injection amount Qd1 that can sufficiently exert the effect in the fuel injection in the compression stroke without setting each required minimum fuel injection amount based on the minimum required fuel injection amount Qd1min. it can.

  Further, in the present embodiment, when the required fuel injection amount Qfin is corrected to decrease, each target fuel is sequentially selected from the fuel injection in the first half of the intake stroke with the low priority among the fuel injections from the direct injection injector 7. The injection amounts Qd1 to Qd3 are reduced.

  When the target fuel injection amounts Qd1 to Qd3 are reduced, the target fuel injection amounts Qd1 to Qd3 after the reduction are set to the minimum required fuel injections set for each fuel injection from the direct injection injector 7, respectively. The amount Qd1min to Qd3min are not reduced below each other. Specifically, when the required fuel injection amount Qfin is corrected to be reduced, the reduction is first corrected until the target fuel injection amount Qd3 in the fuel injection in the first half of the intake stroke with the lowest priority becomes the required minimum fuel injection amount Qd3min. . Next, when the required amount of reduction cannot be satisfied by this amount of reduction correction, the target fuel injection amount Qd2 in the fuel injection in the second half of the intake stroke with the next lowest priority becomes the required minimum fuel injection amount Qd2min. Until weight loss is corrected. Finally, when the required amount of reduction cannot be satisfied by these amount of reduction corrections, the amount of reduction is reduced until the target fuel injection amount Qd1 in the fuel injection in the highest priority compression stroke becomes the required minimum fuel injection amount Qd1min. It is corrected. If the required amount of reduction cannot be satisfied even by such a reduction correction, the target fuel injection amount Qp required for the port injector 6 is corrected to be reduced.

  Next, the injection amount calculation routine will be described with reference to FIG. This injection amount calculation routine is periodically executed through an electronic controller 16 at an angle interruption for each predetermined crank angle.

  As shown in FIG. 8, in this routine, the electronic control unit 16 first obtains the required fuel injection amount Qfin of the internal combustion engine 1 based on the engine operating state such as the engine speed and the engine load (step S1).

  Next, the electronic control unit 16 sets the fuel injection amount in the compression stroke in the direct injection injector 7 to an optimum value for the engine operating state at that time based on the engine operating state such as the engine speed and the engine load and the direct injection pressure. A first fuel injection period d1 for setting (the above required value) is calculated (step S2).

  Then, the electronic control unit 16 calculates the target fuel injection amount Qd1 by multiplying the first fuel injection period d1 by the direct injection pressure (step S3).

  Next, the electronic control unit 16 determines whether or not the target fuel injection amount Qd1 is equal to or less than the required fuel injection amount Qfin (step S4). If the determination is negative, the electronic control unit 16 replaces the target fuel injection amount Qd1 with the required fuel injection amount Qfin (step S5). On the other hand, if the determination is affirmative, the electronic control unit 16 maintains the target fuel injection amount Qd1 calculated in step S3, and proceeds to step S6.

  The electronic control unit 16 calculates the remaining amount Q1 by subtracting the target fuel injection amount Qd1 from the required fuel injection amount Qfin (step S6).

  Thereafter, the electronic control unit 16 calculates a second fuel injection period d2 for setting the fuel injection amount in the latter half of the intake stroke in the direct injection injector 7 to an optimum value (the above-mentioned required value) for the engine operating state at that time. (Step S7).

  Then, the electronic control unit 16 calculates the target fuel injection amount Qd2 by multiplying the second fuel injection period d2 by the direct injection pressure (step S8).

  Next, the electronic control unit 16 determines whether or not the target fuel injection amount Qd2 is less than or equal to the remaining amount Q1 (step S9). If a negative determination is made here, the electronic control unit 16 replaces the target fuel injection amount Qd2 with the remaining amount Q1 (step S10). On the other hand, if the determination is affirmative, the electronic control unit 16 maintains the target fuel injection amount Qd2 calculated in step S8, and proceeds to step S11.

  The electronic control unit 16 calculates the remaining amount Q2 by subtracting the target fuel injection amount Qd2 from the remaining amount Q1 (step S11).

  Thereafter, the electronic control unit 16 calculates a third fuel injection period d3 for setting the fuel injection amount in the first half of the intake stroke in the direct injection injector 7 to an optimum value (the above required value) for the engine operating state at that time. (Step S12).

  Then, the electronic control unit 16 calculates the target fuel injection amount Qd3 by multiplying the third fuel injection period d3 by the direct injection pressure (step S13).

  Next, the electronic control unit 16 determines whether or not the target fuel injection amount Qd3 is less than or equal to the remaining amount Q2 (step S14). If a negative determination is made here, the electronic control unit 16 replaces the target fuel injection amount Qd3 with the remaining amount Q2 (step S15). On the other hand, if the determination is affirmative, the electronic control unit 16 maintains the target fuel injection amount Qd3 calculated in step S13, and proceeds to step S16.

  The electronic control unit 16 calculates the remaining amount Q3 by subtracting the target fuel injection amount Qd3 from the remaining amount Q2 (step S16). Next, the electronic control unit 16 sets the remaining amount Q3 as the target fuel injection amount Qp in the fuel injection by the port injector 6 (step S17), and ends this routine.

  Next, the first fuel injection period calculation routine will be described with reference to FIG. This first fuel injection period calculation routine is a subroutine for calculating the first fuel injection period d1 in step S2 (see FIG. 8) of the injection amount calculation routine, and is executed through the electronic control device 16 every time the process proceeds to step S2. .

  As shown in FIG. 9, in this routine, the electronic control unit 16 first determines whether or not the current engine operating state is within a region in which fuel injection is performed in the compression stroke from the direct injection injector 7 ( Step S101). If the determination is affirmative, the electronic control unit 16 determines whether or not the direct injection pressure is within a region where fuel injection can be performed in the compression stroke (step S102). If the determination is affirmative, the electronic control unit 16 calculates the first fuel injection period d1 with reference to the map based on the engine speed and the engine load (step S103), and ends this routine.

  The first fuel injection period d1 calculated in this way has a value that can form an air-fuel mixture (weak rich air-fuel mixture) that easily ignites the injected fuel around the spark plug 12 in the cylinder 40, for example, in FIG. As shown, the value increases as the engine load increases and the engine speed increases. Further, the first fuel injection period d1 is guarded so as not to exceed the maximum value.

  On the other hand, if a negative determination is made in either step S101 or step S102, the electronic control unit 16 sets the first fuel injection period d1 to “0” so that fuel injection in the compression stroke is not performed. (Step S104), and this routine ends.

  Next, the second fuel injection period calculation routine will be described with reference to FIG. This second fuel injection period calculation routine is a subroutine for calculating the second fuel injection period d2 in step S7 (see FIG. 8) of the injection amount calculation routine, and is executed through the electronic control device 16 every time the process proceeds to step S7. .

  As shown in FIG. 11, the electronic control unit 16 calculates the second fuel injection period d2 with reference to the map based on the engine speed and the engine load (step S201), and ends this routine. For example, as shown in FIG. 12, the second fuel injection period d2 calculated in this way can enhance the air flow in the cylinder 40 by the injected fuel and reduce the amount of injected fuel as much as possible. As the engine load increases and the engine speed increases, the value increases. Further, the second fuel injection period d2 is guarded so as not to exceed the maximum value.

  Next, a third fuel injection period calculation routine will be described with reference to FIGS. 13 and 14. This third fuel injection period calculation routine is a subroutine for calculating the third fuel injection period d3 in step S12 (see FIG. 8) of the injection amount calculation routine, and is executed through the electronic control unit 16 every time the process proceeds to step S12. .

  As shown in FIG. 13, in this routine, the electronic control unit 16 first determines whether or not there is fuel injection in the compression stroke from the direct injection injector 7, for example, the first fuel injection period d1 is longer than “0”. Whether or not (step S301). If the determination is affirmative, the electronic control unit 16 performs a process (steps S302 to S308) for calculating a third fuel injection period d3 corresponding to the situation in which fuel injection is performed in the compression stroke.

  The calculation of the third fuel injection period d3 in this series of processing is based on the MBT, the final ignition timings E and I, and the maximum value α, and the following expression “d3 = α · (MBT−E) / (IE)” ... (1) ”. The MBT in the equation (1) is an ignition timing at which the output torque can be maximized in the internal combustion engine 1 under the situation where fuel injection is performed in the compression stroke. The final ignition timing E is an optimum value of the ignition timing of the internal combustion engine 1 in a situation where fuel injection is performed in the compression stroke and fuel injection is not performed in the first half of the intake stroke from the direct injection injector 7. . In the final ignition timing I, the fuel injection is performed in the compression stroke, and the fuel injection in the first half of the intake stroke is performed to the maximum so that knocking in the internal combustion engine 1 is suppressed. This is the optimum value for the ignition timing. These final ignition timings E and I change, for example, as shown in FIG. The maximum value α is a fuel injection period when the fuel injection in the first half of the intake stroke is performed to the maximum in a situation where fuel injection is performed in the compression stroke.

  Hereinafter, the processing in steps S302 to S308 in FIG. 13 will be described in detail.

  First, the electronic control unit 16 calculates MBT under the condition where fuel injection is performed in the compression stroke based on the engine speed and the engine load (step S302). Thereafter, the electronic control unit 16 uses the reference value of the ignition timing of the internal combustion engine 1 under the condition where fuel injection is performed in the compression stroke and fuel injection is not performed in the first half of the intake stroke from the direct injection injector 7. A certain basic ignition timing is calculated based on the engine operating state (step S303).

  Next, the electronic control unit 16 performs various corrections on the basic ignition timing, such as correction based on the presence or absence of knocking in the internal combustion engine 1 (KCS correction), correction based on the engine water temperature, and correction based on the valve timing of the intake valve 26. Is added to calculate the final ignition timing E (step S304). Further, the electronic control unit 16 performs the fuel injection in the compression stroke and maximizes the fuel injection in the first half of the intake stroke from the direct injection injector 7 so that the knock limit of the internal combustion engine 1 is advanced. A basic ignition timing, which is a reference value for the ignition timing of the internal combustion engine 1 under the raised condition, is also calculated based on the engine operating state (step S305).

  The electronic control unit 16 calculates the final ignition timing I by applying various corrections such as KCS correction, correction based on the engine water temperature, and correction based on the valve timing of the intake valve 26 to the basic ignition timing. (Step S306). Thereafter, the electronic control unit 16 calculates the final ignition timings E and I, and then calculates the maximum value α based on the engine operating state (step S307).

  Next, the electronic control unit 16 uses the expression (1) based on the MBT, the final ignition timings E and I, and the maximum value α, and uses the third fuel injection period corresponding to the situation in which the fuel injection is performed in the compression stroke. d3 is calculated (step S308).

  On the other hand, when the electronic control unit 16 determines in step S301 that there is no fuel injection in the compression stroke from the direct injection injector 7, a third fuel injection period d3 corresponding to a situation in which fuel injection in the compression stroke is not performed. Is performed (steps S309 to S314 shown in FIG. 14).

  The calculation of the third fuel injection period d3 in this series of processing is based on the MBT, the final ignition timing F, J and the maximum value β, and the following equation “d3 = β · (MBT−F) / (J−F) ... (2) ". MBT in the equation (2) is an ignition timing at which the output torque can be maximized in the internal combustion engine 1 in a situation where fuel injection is not performed in the compression stroke. Further, the final ignition timing F is an optimum value of the ignition timing of the internal combustion engine 1 in a situation where fuel injection in the compression stroke is not performed and fuel injection in the first half of the intake stroke from the direct injection injector 7 is not performed. is there. The final ignition timing J is an ignition of the internal combustion engine 1 in a state where the fuel injection in the compression stroke is not performed and the fuel injection in the first half of the intake stroke is performed to the maximum to prevent knocking in the internal combustion engine 1. It is the optimum value of the time. These final ignition timings F and J change, for example, as shown in FIG. Further, the maximum value β is a fuel injection period when the fuel injection in the first half of the intake stroke is performed to the maximum in a situation where the fuel injection in the compression stroke is not performed.

  Hereinafter, the processing in steps S309 to S315 in FIG. 14 will be described in detail.

  First, the electronic control unit 16 calculates MBT under the condition where fuel injection is not performed in the compression stroke based on the engine speed and the engine load (step S309). Thereafter, the electronic control unit 16 uses the reference value of the ignition timing of the internal combustion engine 1 under the situation where the fuel injection in the compression stroke is not performed and the fuel injection in the first half of the intake stroke from the direct injection injector 7 is not performed. A certain basic ignition timing is calculated based on the engine operating state (step S310).

  Next, the electronic control unit 16 calculates the final ignition timing F by applying various corrections such as KCS correction, correction based on the engine water temperature, and correction based on the valve timing of the intake valve 26 to the basic ignition timing. (Step S311). Further, the electronic control unit 16 does not perform fuel injection in the compression stroke, and performs maximum fuel injection in the first half of the intake stroke from the direct injection injector 7 so that the knock limit of the internal combustion engine 1 is advanced. A basic ignition timing, which is a reference value for the ignition timing of the internal combustion engine 1 under the raised condition, is also calculated based on the engine operating state (step S312).

  The electronic control unit 16 calculates the final ignition timing J by applying various corrections such as KCS correction, correction based on the engine water temperature, and correction based on the valve timing of the intake valve 26 to the basic ignition timing. (Step S313). Thereafter, after calculating the final ignition timings F and J, the electronic control unit 16 calculates the maximum value β based on the engine operating state (step S314).

  Next, the electronic control unit 16 uses the equation (2) based on the MBT, the final ignition timing F, J, and the maximum value β, and performs the third fuel injection corresponding to the situation where the fuel injection is not performed in the compression stroke. The period d3 is calculated (step S315).

  When the third fuel injection period d3 is calculated in step S308 or step S315, the third fuel injection period d3 is guarded so as not to exceed its maximum value.

  Thereafter, as shown in FIG. 13, the electronic control unit 16 determines whether or not the third fuel injection period d3 is less than “0” (step S316). If the determination is affirmative, the electronic control unit 16 sets the third fuel injection period d3 to “0” (step S317), and ends this routine. Incidentally, as shown in FIG. 15A, in this example, when the final ignition timing F becomes a value (large value) on the advance side of the MBT in the low load operation region of the internal combustion engine 1, the equation (2) is expressed. The third fuel injection period d3 calculated by using this becomes less than “0”. In such a case, the third fuel injection period d3 is set to “0” through the processing of step S316 and step S317.

  Next, an example of the change of the fuel injection mode in the internal combustion engine 1 with respect to the change of the engine load will be described with reference to FIG.

  In FIG. 15B, fuel injection is performed in the compression stroke from the direct injection injector 7 in the region AR1, and fuel injection is performed in the latter stage of the intake stroke from the direct injection injector 7 in the region AR2. In the area AR3, fuel is injected from the direct injection injector 7 in the first half of the intake stroke, and in the area AR4, fuel is injected from the port injection injector 6.

  As can be seen from the figure, the area AR2 exists over the entire change range of the engine load. The area AR3 is a load area where the engine load is larger than the predetermined value KL1, that is, a load area where the final ignition timing F (see FIG. 15 (a)) is a retarded value (small value) from the MBT. Existing. Further, the area AR1 is a load area where the engine load is larger than the predetermined value KL2, that is, the final ignition timings E and I (see FIG. 15A) are both retarded values (smaller bonds) than the MBT. Exists in the load area.

  When the engine load is the minimum value, fuel injection for the target fuel injection amount Qd2 in the latter half of the intake stroke from the direct injection injector 7 is performed, thereby obtaining the required fuel injection amount Qfin. Thereafter, when the engine load becomes larger than the minimum value, the fuel injection for the target fuel injection rod Qd2 in the latter stage of the intake stroke from the direct injection injector 7 and the port injection injector 6 until the engine load reaches a predetermined value KL1. The fuel injection for the target fuel injection amount Qp is performed, so that the required fuel injection amount Qfin is obtained.

  When the engine load becomes larger than the predetermined value KL1, until the engine load reaches the predetermined value KL2, fuel injection for the target fuel injection amount Qd2 in the latter half of the intake stroke from the direct injection injector 7 and the first half of the intake stroke While the fuel injection for the target fuel injection amount Qd3 is performed, the fuel injection for the target fuel injection amount Qp from the port injector 6 is also performed. The required fuel injection amount Qfin can be obtained by these fuel injections. Further, when the engine load becomes larger than the predetermined value KL2, the fuel injection for the target fuel injection amount Qd1 in the compression stroke from the direct injection injector 7, the fuel injection for the target fuel injection amount Qd2 in the latter stage of the intake stroke, and the intake stroke Fuel injection for the target fuel injection amount Qd3 in the previous period is performed, and the required fuel injection amount Qfin is obtained by these fuel injections.

  As shown in FIG. 15B, in this example, the target fuel injection amount Qd3 is set to a larger value as the engine load increases between the predetermined value KL1 and the predetermined value KL2. Thus, even if the temperature in the cylinder 40 increases as the engine load increases and knocking in the internal combustion engine 1 is likely to occur, the target fuel injection amount Qd3 is increased by the increase in the target fuel injection amount Qd3. The top of the piston 13 is effectively cooled by the fuel injection in the first half of the intake stroke. As a result, the temperature in the cylinder 40 hardly rises and knocking hardly occurs, so that the ignition timing of the internal combustion engine 1 can be advanced toward the MBT, and the internal combustion engine is advanced through the advance of the ignition timing. The output torque of the engine 1 can be increased.

  Next, the ignition timing calculation routine will be described with reference to FIG. This ignition timing calculation routine is periodically executed through the electronic control unit 16, for example, at an angle interruption for each predetermined crank angle.

  As shown in FIG. 16, in this routine, the electronic control unit 16 first determines whether or not there is fuel injection in the compression stroke from the direct injection injector 7 (step S401). If the determination is affirmative, the electronic control unit 16 executes a process (steps S402 to S406) for calculating an ignition timing command value K corresponding to a situation where fuel injection is performed in the compression stroke.

  In this series of processing, the electronic control unit 16 determines the MBT, the final ignition timings E and I, and the maximum value α in the same manner as steps S302, S304, S306, and S307 in the third fuel injection period calculation routine (see FIG. 13). Calculate (step S402).

  Next, the electronic control unit 16 performs fuel injection in the compression stroke based on the calculated final ignition timings E and I and the maximum value α and the third fuel injection period d3 calculated in step S308 of FIG. The ignition timing command value K corresponding to the situation is calculated using the following equation “K = E + (IE) · (d3 / α) (3)” (step S403).

  Thereafter, the electronic control unit 16 determines whether or not the calculated ignition timing command value K is a value (a larger value) on the advance side than the MBT (step S404). If the determination is affirmative, the electronic control unit 16 replaces the ignition timing command value K with MBT (step S405), and ends this routine. On the other hand, if a negative determination is made, the electronic control unit 16 maintains the ignition timing command value K (step S406) and ends this routine.

  On the other hand, when it is determined in step S401 that there is no fuel injection in the compression stroke from the direct injection injector 7, the electronic control unit 16 determines the ignition timing command value corresponding to the situation in which fuel injection is not performed in the compression stroke. Processing for calculating K (steps S407 to S411) is executed.

  In this series of processing, the electronic control unit 16 determines the MBT, the final ignition timing F, J, and the maximum value β in the same manner as steps S309, S311, S313, and S314 of the third fuel injection period calculation routine (see FIG. 14). Calculate (step S407).

  Next, the electronic control unit 16 performs fuel injection in the compression stroke based on the calculated final ignition timings F and J and the maximum value β and the third fuel injection period d3 calculated in step S315 of FIG. An ignition timing command value K corresponding to a situation that is not broken is calculated using the following equation “K = F + (J−F) · (d3 / β) (4)” (step S408).

  Thereafter, the electronic control unit 16 determines whether or not the calculated ignition timing command value K is a value (a larger value) on the advance side than the MBT (step S409). If the determination is affirmative, the electronic control unit 16 replaces the ignition timing command value K with MBT (step S410), and ends this routine. On the other hand, if a negative determination is made, the electronic control unit 16 maintains the ignition timing command value K (step S411) and ends this routine.

  When the ignition timing command value K is thus calculated, the ignition timing of the internal combustion engine 1 is controlled based on the ignition timing command value K. By such ignition timing control, the ignition timing is set to a value along the MBT indicated by a broken line in FIG. 15A as much as possible within a range in which knocking does not occur. Even if the ignition timing becomes a value that is retarded from the value on the MBT, the ignition timing is made as close to the MBT as possible without causing knocking.

  Next, an injection amount reduction correction routine will be described with reference to FIGS. 17 and 18. This injection amount decrease correction routine is executed every time a decrease correction of the required fuel injection amount Qfin by, for example, purge processing or the like occurs through the electronic control unit 16.

  As shown in FIG. 17, in this routine, the electronic control unit 16 first calculates a reduction amount QM of the required fuel injection amount Qfin (step S501). In the present embodiment, the purge correction amount fpg due to the purge process is calculated as the decrease amount QM. In this embodiment, when the required fuel injection amount Qfin is corrected to decrease, first, the target fuel injection amount on the direct injection injector 7 side (the target fuel injection amounts Qd1 to Qd3 set for each of a plurality of fuel injections). (Total value) is corrected for weight loss. Therefore, in the present embodiment, reducing the required fuel injection amount Qfin is equivalent to reducing the fuel injection amount required for the direct injection injector 7.

  Next, the electronic control unit 16 calculates a required minimum fuel injection amount Qd3min in the first half of the intake stroke in the direct injection injector 7 (step S502). Specifically, the electronic control unit 16 calculates a third minimum required fuel injection period d3min for setting the required minimum fuel injection amount Qd3min to an optimum value according to the engine operating state and the engine water temperature at that time, The required minimum fuel injection amount Qd3min is calculated by multiplying this by the direct injection pressure. At this time, the required minimum fuel injection amount Qd3min calculated as an optimum value is larger than the minimum fuel injection amount that can be injected by the direct injection injector 7, and is set by the fuel injection in the first half of the intake stroke from the direct injection injector 7 The value is smaller than the requested value. The third minimum required fuel injection period d3min is set to overlap with the third fuel injection period d3 as shown in FIG.

  Thereafter, the electronic control unit 16 subtracts the required minimum fuel injection amount Qd3min from the target fuel injection amount Qd3 set in the above-described injection amount calculation routine (see FIG. 8) to obtain the third reduction amount Qd3de (see FIG. 18). Calculate (step S503).

  Next, the electronic control unit 16 determines whether or not a value obtained by subtracting the third reduction amount Qd3de from the reduction amount QM is greater than 0 (step S504). If a negative determination is made here, the electronic control unit 16 replaces the target fuel injection amount Qd3 with a value obtained by subtracting the decrease amount QM from the target fuel injection amount Qd3 (Qd3-QM) (step S505). On the other hand, if the determination is affirmative, the electronic control unit 16 replaces the target fuel injection amount Qd3 with the necessary minimum fuel injection amount Qd3min (step S506), and proceeds to step S507.

  The electronic control unit 16 calculates the remaining reduction amount QM1 (step S507). Specifically, the electronic control unit 16 can calculate the value obtained by subtracting the third reduction amount Qd3de from the reduction amount QM obtained in step S504 as the remaining reduction amount QM1.

  Next, the electronic control unit 16 calculates a necessary minimum fuel injection amount Qd2min in the latter half of the intake stroke in the direct injection injector 7 (step S508). Specifically, the electronic control unit 16 calculates a second minimum required fuel injection period d2min for setting the required minimum fuel injection amount Qd2min to an optimum value according to the engine operating state and the engine water temperature at that time, The required minimum fuel injection amount Qd2min is calculated by multiplying this by the direct injection pressure. At this time, the required minimum fuel injection amount Qd2min calculated as an optimum value is larger than the minimum fuel injection amount that can be injected by the direct injection injector 7, and is set by fuel injection in the latter stage of the intake stroke from the direct injection injector 7 The value is smaller than the requested value. The second minimum required fuel injection period d2min is set to overlap with the second fuel injection period d2, as shown in FIG.

  Thereafter, the electronic control unit 16 subtracts the required minimum fuel injection amount Qd2min from the target fuel injection amount Qd2 set in the above-described injection amount calculation routine (see FIG. 8) to obtain the second reduction amount Qd2de (see FIG. 18). Calculate (step S509).

  Next, the electronic control unit 16 determines whether or not a value obtained by subtracting the second reduction amount Qd2de from the remaining reduction amount QM1 is greater than 0 (step S510). If a negative determination is made here, the electronic control unit 16 replaces the target fuel injection amount Qd2 with a value obtained by subtracting the remaining amount QM1 from the target fuel injection amount Qd2 (Qd2-QM1) (step S511). On the other hand, if the determination is affirmative, the electronic control unit 16 replaces the target fuel injection amount Qd2 with the necessary minimum fuel injection amount Qd2min (step S512), and proceeds to step S513.

  The electronic control unit 16 calculates the remaining reduction amount QM2 (step S513). Specifically, the electronic control unit 16 can calculate the value obtained by subtracting the second reduction amount Qd2de from the residual reduction amount QM1 obtained in step S510 as the residual reduction amount QM2.

  Next, the electronic control unit 16 calculates a required minimum fuel injection amount Qd1min in the compression stroke in the direct injection injector 7 (step S514). Specifically, the electronic control unit 16 calculates a first minimum required fuel injection period d1min for setting the required minimum fuel injection amount Qd1min to an optimum value according to the engine operating state and the engine water temperature at that time, The required minimum fuel injection amount Qd1min is calculated by multiplying this by the direct injection pressure. At this time, the required minimum fuel injection amount Qd1min calculated as an optimum value is larger than the minimum fuel injection amount that can be injected by the direct injection injector 7, and is set by the fuel injection in the compression stroke from the direct injection injector 7. The value is smaller than the required value. The first minimum required fuel injection period dmin is set to overlap with the first fuel injection period d1, as shown in FIG.

  Thereafter, the electronic control unit 16 subtracts the required minimum fuel injection amount Qd1min from the target fuel injection amount Qd1 set in the above-described injection amount calculation routine (see FIG. 8) to obtain the first reduction amount Qd1de (see FIG. 18). Calculate (step S515).

  Next, the electronic control unit 16 determines whether or not a value obtained by subtracting the first reduction amount Qd1de from the remaining reduction amount QM2 is greater than 0 (step S516). If a negative determination is made here, the electronic control unit 16 replaces the target fuel injection amount Qd1 with a value obtained by subtracting the remaining amount QM2 from the target fuel injection amount Qd1 (Qd1-QM2) (step S517). On the other hand, if the determination is affirmative, the electronic control unit 16 replaces the target fuel injection amount Qd1 with the necessary minimum fuel injection amount Qd1min (step S518), and proceeds to step S519.

  The electronic control unit 16 calculates the remaining reduction amount QM3 (step S519). Specifically, the electronic control unit 16 can calculate the value obtained by subtracting the first reduction amount Qd1de from the residual reduction amount QM2 obtained in step S516 as the residual reduction amount QM3.

  Next, the electronic control unit 16 subtracts the remaining fuel amount QM3 from the target fuel injection amount Qp set in the above-described injection amount calculation routine (see FIG. 8), for the target fuel injection amount Qp in the fuel injection in the port injector 6. (Qp-QM3) is replaced (step S520), and this routine is terminated.

  As described above, in the electronic control device 16 according to the present embodiment, the fuel injection amount required in the direct injection injector 7 (in this embodiment, the required fuel injection amount Qfin) is corrected to decrease by, for example, a purge process. In this case, among the multiple fuel injections from the direct injection injector 7 (respective fuel injections in the compression stroke, the latter half of the intake stroke, and the first half of the intake stroke), each target fuel injection amount Qd1 Decrease each Qd3. At this time, the target fuel injection amounts Qd1 to Qd3 after the reduction are made not to be lower than the necessary minimum fuel injection amounts Qd1min to Qd3min, respectively.

  Thereby, for example, even when the fuel injection amount required for the direct injection injector 7 is corrected to be reduced by purging or the like, any fuel injection from the direct injection injector 7 is not performed. It is possible to prevent a situation in which the set target fuel injection amount is less than the required minimum fuel injection amount. For this reason, at least the minimum required fuel injection amount Qd1min to Qd3min can be ensured in each fuel injection from the direct injection injector 7.

  As described above, the electronic control unit 16 according to the present embodiment can perform multiple times per combustion cycle of the internal combustion engine even when the fuel injection amount required for the direct injector 7 is reduced. In each fuel injection from the divided direct injection injector 7, it is possible to secure a fuel injection amount necessary for contributing to improvement in combustion.

  In addition, the electronic control unit 16 according to the present embodiment is used to ignite the internal combustion engine 1 among a plurality of fuel injections from the direct injection injector 7 (respective fuel injections in the compression stroke, the late intake stroke and the early intake stroke). The nearer the fuel injection, the higher the priority. This is because, among the fuel injections from the direct injection injector 7, the closer to the ignition timing of the internal combustion engine 1, the greater the influence of ignition on the fuel due to the difference in the fuel injection amount. This is because the closer to the ignition timing, the higher the priority. As a result, the fuel injection having a greater influence on the fuel can preferentially secure the target fuel injection amount, so that the combustion state of the internal combustion engine 1 can be improved.

  Further, the electronic control unit 16 according to the present embodiment performs the fuel injection (first fuel injection) in the compression stroke close to the ignition timing of the internal combustion engine 1 and the compression as the fuel injection from the direct injector 7 a plurality of times. Fuel injection in the second half of the intake stroke that is farther from the ignition timing than fuel injection in the stroke (second fuel injection), and fuel injection in the first half of the intake stroke that is farther from the ignition timing than fuel injection in the second half of the intake stroke 3 fuel injection).

  As a result, the electronic control unit 16 according to the present embodiment performs fuel injection in the compression stroke so that the injected fuel can be easily collected around the spark plug 12 by the airflow in the cylinder 40 and the like. The combustion speed of the fuel can be improved by improving the ignition of the fuel. Further, when the fuel injection is performed in the latter stage of the intake stroke, when the moving speed of the piston 13 becomes slow and the generation of the air flow in the cylinder 40 due to the movement of the piston 13 becomes weak, the air flow in the cylinder 40 is strengthened and good fuel is produced. Burning can be obtained. Furthermore, by performing fuel injection in the first half of the intake stroke, it becomes possible to make the injected fuel adhere directly to the top of the piston 13. As a result, the top of the piston 13 can be cooled by the latent heat of vaporization of the fuel, so that the occurrence of knocking in the internal combustion engine 1 can be suppressed.

  Further, the electronic control unit 16 according to the present embodiment sets the necessary minimum fuel injection amounts Qd1min to Qd3min larger than the minimum fuel injection amount that can be injected by the direct injection injector 7 and each fuel from the direct injection injector 7. The value is set smaller than the required value set for injection. Thereby, each of the minimum required fuel injection amounts Qd1min to Qd3min can be set to a fuel injection amount greater than a predetermined amount necessary to obtain each effect corresponding to each fuel injection from the direct injection injector 7. In addition, the above-described effects can be obtained without depending on the performance of the direct injection injector 7.

  Note that the priority of each fuel injection from the direct injection injector 7 in the present embodiment is not limited to the priority order shown in the present embodiment, and is appropriately changed according to the operating state of the internal combustion engine 1 and the like. May be. For example, when the temperature in the cylinder 40 of the internal combustion engine 1 rises excessively and is in an operating state in which knocking is likely to occur, the priority of fuel injection in the first half of the intake stroke can be increased.

  In the present embodiment, when the required fuel injection amount Qfin is corrected to decrease, first, the target fuel injection amounts Qd1 to Qd3 on the direct injection side are corrected to decrease, and then the target fuel injection on the port injector side is performed. Although the amount Qp is corrected to decrease, the present invention is not limited to this. For example, after the target fuel injection amount Qp on the port injector side is corrected to decrease, the amount of decrease that cannot be reduced by the amount reduction correction is reduced to the direct injection side. The target fuel injection amounts Qd1 to Qd3 may be corrected to decrease in order of increasing priority. In this case, the reduction amount QM calculated in step S501 of FIG. 17 is a reduction amount that cannot be reduced with respect to the target fuel injection amount Qp in the purge correction amount fpg. For example, if the amount of decrease with respect to the target fuel injection amount Qp is Qpde, the amount of decrease QM is a value obtained by subtracting the amount of decrease Qpde from the purge correction amount fpg.

  Further, in the present embodiment, as an example of the decrease correction of the required fuel injection amount Qfin, the case of the purge process is mentioned, but the case where the decrease correction is performed by a process other than the purge process is also included.

  Further, in the present embodiment, the electronic control device 16 applied to the internal combustion engine 1 including the port injection injector 6 and the direct injection injector 7 has been described. However, the present invention is not limited thereto, and for example, only the direct injection injector 7 is provided. It is also possible to apply to an internal combustion engine. In this case, in the injection amount calculation routine (see FIG. 8), the target fuel injection amount Qd3 having the lowest priority among the target fuel injection amounts Qd1 to Qd3 in each fuel injection from the direct injection injector 7 is set last. Is called. Further, in this case, when the total value of the target fuel injection amounts Qd1 to Qd3 is less than the required fuel injection amount Qfin, the fuel amount that is not satisfied is injected from the direct injection injector 7 by fuel injection in the first half of the intake stroke. It is preferable. As a result, of the fuel for the required fuel injection amount Qfin, fuel that cannot be injected in the latter half of the compression stroke and the intake stroke is injected into the cylinder 40 in the first half of the intake stroke.

  By performing such fuel injection, in order to obtain the required fuel injection amount Qfin, each fuel injection amount in each fuel injection in the latter half of the compression stroke and the intake stroke exceeds the target fuel injection amounts Qd1 and Qd2, respectively. Can be prevented. Thereby, it is possible to suppress adverse effects on the fuel. Note that such a fuel injection mode of the direct injection injector 7 can also be employed for fuel injection control of the internal combustion engine 1 including the port injection injector 6 and the direct injection injector 7 as in the present embodiment.

  In the present embodiment, the fuel injection from the direct injection injector 7 is performed three times per combustion cycle. However, the present invention is not limited to this. For example, the fuel injection may be performed twice or four times or more. Good. Further, the fuel injection from the direct injection injector 7 in the compression stroke may be divided into, for example, the first half of the compression stroke and the second half of the compression stroke. That is, the injection mode of the direct injection injector 7 shown in the present embodiment is an example and is not limited to this.

  As described above, the fuel injection control device for an internal combustion engine according to the present invention includes a plurality of fuel injections per combustion cycle of the internal combustion engine even when the fuel injection amount required for the direct injection injector is reduced. The fuel injection amount required to contribute to the improvement of combustion in each fuel injection from the direct injection injector divided into multiple times can be secured, and the direct injection that injects the fuel directly into at least the cylinder as an injector for fuel injection This is useful for a fuel injection control device for an internal combustion engine equipped with an injector.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2a Intake port 6 Port injection injector 7 Direct injection injector 16 Electronic control apparatus (fuel injection control apparatus of internal combustion engine)
40 cylinders

Claims (6)

A direct injection injector capable of multiple fuel injections into a cylinder of the internal combustion engine per combustion cycle of the internal combustion engine is provided, so that at least a part of the required fuel injection amount required based on the engine operating state can be obtained. A fuel injection control device for an internal combustion engine that performs fuel injection from the direct injection injector,
The target fuel injection amount for the plurality of fuel injections from the direct injection injector is set to a required value corresponding to the engine operating state, and the minimum fuel injection required for each of the plurality of fuel injections from the direct injection injector Set each amount,
When the fuel injection amount required for the direct injection injector among the required fuel injection amounts is corrected to decrease, among the plurality of fuel injections from the direct injection injector, the fuel injections in order of lower priority are sequentially performed. When reducing the target fuel injection amount and reducing the target fuel injection amount, the target fuel injection amount after the reduction is set to the required minimum fuel set for each of the plurality of fuel injections from the direct injection injector A fuel injection control device for an internal combustion engine, characterized in that the fuel injection amount does not fall below an injection amount.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein among the plurality of fuel injections from the direct injection injector, the priority is higher in the fuel injection at a timing closer to the ignition of the internal combustion engine.   The required minimum fuel injection amount is a value that is larger than the minimum fuel injection amount that can be injected by the direct injection injector and smaller than the required value that is set for each of the plurality of fuel injections from the direct injection injector. The fuel injection control device for an internal combustion engine according to claim 1 or 2, wherein   The fuel for an internal combustion engine according to any one of claims 1 to 3, wherein the minimum fuel injection amount is increased as the internal combustion engine enters a high speed / high load operation state. Injection control device.   As the plurality of fuel injections from the direct injection injector, a first fuel injection that injects fuel in a compression stroke close to ignition of the internal combustion engine, and an intake stroke that is farther from the ignition than the first fuel injection The second fuel injection for injecting fuel and the third fuel injection for injecting fuel in an intake stroke farther from the ignition than the second fuel injection are performed. A fuel injection control device for an internal combustion engine according to claim 1. The internal combustion engine includes a port injection injector capable of fuel injection toward an intake port of the internal combustion engine,
6. The fuel according to claim 1, wherein fuel that cannot be injected by the plurality of times of fuel injection from the direct injection injector among the required fuel injection amount is injected from the port injector. A fuel injection control device for an internal combustion engine according to claim 1.

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