JP4501108B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to an in-cylinder injector that injects fuel into a cylinder and an intake-path injector that injects fuel into an intake passage or an intake port. And a fuel injection control device for an internal combustion engine including valve timing changing means.

  In general, it is known that when the engine is cold, particularly when the engine is cold, the fuel is not sufficiently vaporized and the startability is reduced. Various proposals have been made to deal with this. For example, in Patent Document 1, in an engine control device having an intake passage injection injector that injects fuel into an intake passage, the valve timing changing means sets the closing timing of the exhaust valve before the exhaust top dead center. And the crank angle from the exhaust valve close timing to the exhaust top dead center is set to be larger than the crank angle from the exhaust top dead center to the intake valve open timing, and By using the fuel injection timing from the fuel injection valve as the valve opening timing of the intake valve, the fuel using the temperature rise of the fuel injection field due to the blowback of the combustion gas and the subsequent rapid growth of negative pressure A technique is disclosed in which startability is improved by promoting vaporization of the fuel.

  In addition, an in-cylinder injector for injecting fuel into the cylinder and an intake-path injector for injecting fuel into the intake passage or the intake port are provided according to the operating state of the engine. A so-called dual injection type internal combustion engine that realizes stratified combustion in the low load operation region and homogeneous combustion in the high load operation region by improving the fuel efficiency and output characteristics by switching these injectors. Are known.

JP 2002-147272 A

  However, the technique described in Patent Document 1 relates to an engine control device having only an intake passage injection injector that injects fuel into the intake passage, and is mainly related to control after the initial explosion is completed. In the case of the dual injection type internal combustion engine as described above, there is room for further improvement.

  That is, in order to form a startable air-fuel mixture in the cylinder at the start of the engine when it is cold, particularly when it is cold, a certain amount of fuel adheres to the intake passage wall including the cylinder and the port. However, as in the technique described in Patent Document 1, even if fuel injection is performed in accordance with the setting of the valve operating system to a predetermined opening / closing timing by the valve timing changing means, the fuel adheres as described above. Therefore, there is a problem that it takes time to form a gas mixture that can be started, and as a result, the cranking time is prolonged and the startup takes time.

  In particular, in an engine equipped with a mechanical valve timing changing means, it is necessary to set the valve operating system at the optimal valve timing position for starting as described above. However, drive hydraulic pressure is generated during cranking at the time of starting. Since it is not sufficient, it takes time to set it, but there is a problem that if fuel is injected without taking the delay into consideration, the fuel efficiency and emission during that time deteriorate.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can improve the startability of the engine and reduce the deterioration of fuel consumption and emission.

  A fuel injection control device for an internal combustion engine according to one aspect of the present invention that achieves the above object is an in-cylinder injector that injects fuel into a cylinder or an intake passage that injects fuel into an intake passage. In an internal combustion engine equipped with either one or both of the injectors, a fuel injection mode changing means for changing the fuel injection mode by the in-cylinder injector or the intake passage injector, and at least changing the opening / closing timing of the intake valve And a valve timing changing means for performing the fuel injection after the opening / closing timing including at least the operating angle of the intake valve is changed to a predetermined timing by the valve timing changing means when the engine is started. It is changed by the changing means before and after the change to the predetermined timing. And butterflies.

  Further, when only one of the in-cylinder injector or the intake manifold injector is provided, the fuel injection form before the change to the predetermined timing is fuel-free injection, and after the change to the predetermined timing The fuel injection form may be any one of the fuel injection starts.

  Further, when both the in-cylinder injector and the intake passage injector are provided, the fuel injection mode is changed by in-cylinder fuel injection by the in-cylinder injector only, intake by only the intake passage injector. Intra-passage fuel injection, change to any of the fuel injection sources including fuel injection by both the in-cylinder injector and the intake passage injector, or the fuel injection amount, fuel injection timing by the same fuel injection source, and Any change in the fuel injection control value including the sharing ratio may be used.

  According to the fuel injection control device for an internal combustion engine according to one aspect of the present invention, either the in-cylinder injector that injects fuel into the cylinder or the intake-path injector that injects fuel into the intake passage On the other hand, in an internal combustion engine equipped with both of these, when the engine is started, the valve timing changing means changes the opening / closing timing including at least the operating angle of the intake valve to a predetermined timing, and then the fuel injection form changing means The fuel injection form by the injector for injection or the injector for intake passage injection is changed. Therefore, when the opening / closing timing including at least the operating angle of the intake valve is set at the optimal valve timing position for starting, the fuel injection mode can be changed to match the opening / closing timing, so that a good mixture is formed. The engine can be started in a short time without failure without excessive fuel injection.

  Further, when only one of the in-cylinder injector or the intake manifold injector is provided, the fuel injection form before the change to the predetermined timing is fuel-free injection, and after the change to the predetermined timing According to the mode in which the fuel injection mode is the start of fuel injection, the discharge of unignited unburned gas during cranking is suppressed, so that deterioration of fuel consumption and emission can be reduced.

  Further, when both the in-cylinder injector and the intake passage injector are provided, the change in the fuel injection mode is in-cylinder fuel injection by the in-cylinder injector only, intake by only the intake passage injector. Intra-passage fuel injection, change to any of the fuel injection sources including fuel injection by both the in-cylinder injector and the intake passage injector, or the fuel injection amount, fuel injection timing by the same fuel injection source, and According to the mode in which any one of the fuel injection control values including the sharing rate is changed, the fuel injection control value can be changed to the fuel injection source or the fuel injection control value that matches the opening / closing timing. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, referring to FIG. 1 showing a schematic configuration diagram of a fuel injection control device for a dual injection internal combustion engine according to the present invention, the engine 1 includes four cylinders 1a. Each cylinder 1 a is connected to a common surge tank 3 via a corresponding intake branch pipe 2. The surge tank 3 is connected to an air flow meter 4 a through an intake duct 4, and the air flow meter 4 a is connected to an air cleaner 5. A throttle valve 7 driven by a step motor 6 is disposed in the intake duct 4. On the other hand, each cylinder 1 a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9.

  Each cylinder 1a is provided with an in-cylinder injector 11 for injecting fuel into the cylinder and an intake passage injector 12 for injecting fuel into the intake port. These injectors 11 and 12 are controlled based on the output signal of the electronic control unit 30. Further, each in-cylinder injector 11 is connected to a common fuel distribution pipe 13, and this fuel distribution pipe 13 is connected to a fuel distribution pipe 13 through a check valve 14, and is driven by an engine drive type. A high-pressure fuel pump 15 is connected.

  As shown in FIG. 1, the discharge side of the high-pressure fuel pump 15 is connected to the suction side of the high-pressure fuel pump 15 via a spill electromagnetic valve 15a. When the amount of fuel supplied from the pump 15 into the fuel distribution pipe 13 is increased and the spill electromagnetic valve 15a is fully opened, the fuel supply from the high pressure fuel pump 15 to the fuel distribution pipe 13 is stopped. ing. The spill electromagnetic valve 15a is controlled based on the output signal of the electronic control unit 30.

  On the other hand, each intake passage injector 12 is connected to a common fuel distribution pipe 16, and the fuel distribution pipe 16 and the high pressure fuel pump 15 are connected to a common fuel pressure regulator 17 through an electric motor drive type low pressure fuel pump. 18 is connected. Further, the low pressure fuel pump 18 is connected to the fuel tank 20 via the fuel filter 19. The fuel pressure regulator 17 returns a part of the fuel discharged from the low-pressure fuel pump 18 to the fuel tank 20 when the fuel pressure of the fuel discharged from the low-pressure fuel pump 18 becomes higher than a predetermined set fuel pressure. Accordingly, the fuel pressure supplied to the intake manifold injector 12 and the fuel pressure supplied to the high-pressure fuel pump 15 are prevented from becoming higher than the set fuel pressure. Further, as shown in FIG. 1, a flow valve 21 is provided between the high pressure fuel pump 15 and the fuel pressure regulator 17. The flow valve 21 is normally opened. When the flow valve 21 is closed, the fuel supply from the low pressure fuel pump 18 to the high pressure fuel pump 15 is stopped. The opening / closing of the flow valve 21 is controlled based on the output signal of the electronic control unit 30.

  The electronic control unit 30 is composed of a digital computer and includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, and an input port which are connected to each other via a bidirectional bus 31. 35 and an output port 36. The air flow meter 4 a generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 4 a is input to the input port 35 via the AD converter 37. A water temperature sensor 38 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine 1, and the output voltage of the water temperature sensor 38 is input to the input port 35 via the AD converter 39.

  A fuel pressure sensor 40 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 13 is attached to the fuel distribution pipe 13, and the output voltage of the fuel pressure sensor 40 is supplied to the input port 35 via the AD converter 41. Entered. An oxygen concentration sensor 42 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 8 upstream of the catalyst 9. The output voltage of the oxygen concentration sensor 42 is input to an input port 35 via an AD converter 43. Is input. The accelerator pedal 10 is connected to an accelerator opening sensor 44 that generates an output voltage proportional to the depression amount of the accelerator pedal 10, and the output voltage of the accelerator opening sensor 44 is input to the input port 35 via the AD converter 45. . The input port 35 is connected to a rotational speed sensor 46 that generates an output pulse representing the engine rotational speed. Further, a starter switch 49 for detecting a starter on / off signal is connected to the input port 35. The ROM 32 of the electronic control unit 30 stores the value of the fuel injection amount and the engine that are set corresponding to the operating state based on the engine load and the engine speed obtained by the accelerator opening sensor 44 and the engine speed sensor 46 described above. Correction values and the like based on the cooling water temperature are preliminarily mapped and stored.

  Furthermore, FIG. 2 shows a side sectional view of the cylinder 1a. Referring to FIG. 2, 61 is a cylinder block, 62 is a piston having a recess 62a formed on the top surface, 63 is a cylinder head secured on the cylinder block 61, and 64 is between the piston 62 and the cylinder head 63. The formed combustion chamber, 65 is an intake valve, 66 is an exhaust valve, 67 is an intake port, 68 is an exhaust port, and 69 is an ignition plug. The intake port 67 is formed so that the air flowing into the combustion chamber 64 generates a swirling flow around the cylinder axis. The recess 62 a extends from the peripheral edge of the piston 62 located on the in-cylinder injector 11 side toward the center of the piston 62 and extends upward below the spark plug 69.

  Here, the variable valve timing mechanism of the engine 1 will be described. As is well known, the crankshaft of the engine 1 is rotated by an intake camshaft and an exhaust camshaft respectively disposed in the cylinder head 63, a crank pulley fixed to the crankshaft, a timing belt, an intake cam pulley, and an exhaust cam pulley. The crankshaft and the camshaft are set to have a 2-to-1 rotation angle. The intake cam provided on the intake camshaft and the exhaust cam provided on the exhaust camshaft (both not shown) are rotated by each camshaft maintained at a 2-to-1 rotation angle with the crankshaft. Based on this, the intake valve 65 and the exhaust valve 66 are opened and closed.

  Between the intake camshaft and the intake cam pulley, the intake cam pulley and the intake camshaft are relatively rotated to continuously change the rotation phase (displacement angle) of the intake camshaft with respect to the crankshaft and the lift amount of the intake valve 65. A hydraulically driven intake variable valve timing mechanism 70 is disposed. As is well known, the intake variable valve timing mechanism 70 is hydraulically switched by an oil control valve such as a linear solenoid valve or a duty solenoid valve, and operates according to a drive signal from the aforementioned ECU 30 for engine control. .

  Similarly, between the exhaust camshaft and the exhaust cam pulley, the exhaust cam pulley and the exhaust camshaft are relatively rotated to continuously change the rotation phase (displacement angle) of the exhaust camshaft with respect to the crankshaft. The exhaust variable valve timing mechanism 71 is provided. Similar to the intake variable valve timing mechanism 70 on the intake side, the exhaust variable valve timing mechanism 71 is hydraulically switched by an oil control valve, and operates according to a drive signal from the engine control ECU 30 described above.

  The intake variable valve timing mechanism 70 on the intake side and the exhaust variable valve timing mechanism 71 on the exhaust side have a cam rotor fixed to the intake camshaft and the exhaust camshaft as a sensor for detecting the operation position thereof. An intake-side cam position sensor 72 and an exhaust-side cam position sensor 73 are provided for detecting a plurality of protrusions formed on the outer periphery at equal angles and outputting a cam position pulse representing the cam position. A lift sensor 74 that detects the lift amount of the intake valve 65 based on the slide amount of the intake camshaft is provided on the intake side as necessary.

  In addition, the intake variable valve timing mechanism 70 and the exhaust variable valve timing mechanism 71 may be replaced with the intake valve by using electromagnetic force generated when an excitation current is applied, instead of the above-described mechanical type using hydraulic pressure. 65 and the exhaust valve 66 may be configured by an electromagnetic drive mechanism that advances and retracts. In this case, the timing of opening and closing and the lift amount can be arbitrarily controlled based on the signal of the electronic control unit 30. Therefore, for example, when operated based on a signal from the electronic control unit 30, the opening / closing timing of the intake valve 65 and / or the exhaust valve 66, and thus the open period (working angle) is long or short, and the lift amount is further increased. It will be variably controlled.

  Here, the output port 36 of the electronic control unit 30 is connected to the step motor 6, each in-cylinder injector 11, each intake passage injector 12, the spill solenoid valve 15 a, the flow valve 21, via the corresponding drive circuit 47. The intake variable valve timing mechanism 70 and the exhaust variable valve timing mechanism 71 are connected to oil control valves.

  Next, an example of the control at the start of the embodiment of the present invention having the above configuration will be described below with reference to the flowchart shown in FIG. First, when control is started by turning on an accessory switch (not shown), the electric motor driven low-pressure fuel pump 18 is started to drive, the flow valve 21 is opened, and the spill electromagnetic valve 15a is kept closed. Therefore, in step S301, a determination is made as to whether or not the engine is starting. The determination as to whether or not the engine is in a starting state is made based on whether or not the starter switch 49 is turned on or whether or not a predetermined condition is satisfied from the first explosion as described later. In the case of starting, the process proceeds to step S302, and the cooling water temperature of the engine 1, which is a detection value from the water temperature sensor 38, is read. Then, the process proceeds to step S303, and the opening / closing timing including the optimum operating angle of the intake valve 65 that is mapped and stored in the ROM 32 is obtained as a target value based on the cooling water temperature. In step S304, the oil control valve of the intake variable valve timing mechanism 70 is controlled, and a change toward the setting of the opening / closing timing of the intake valve 65 to the target value is started.

  Next, in step S305, the output of the cam position sensor 72 is read, and the cam position is calculated from the output value. Then, the process proceeds to step S306, and it is determined whether or not the setting to the target opening / closing timing is completed depending on whether or not the cam position satisfies the target opening / closing timing obtained in step S303. As a result of the determination, when the setting is completed, in other words, when it is changed to a predetermined target opening / closing timing, the process proceeds to step S307, and fuel injection is started as described later. On the other hand, if it is not a start time in the determination in step S301, this routine is terminated. If it is not changed to the predetermined target opening / closing timing in the determination in step S306, the process proceeds to step S308, and fuel injection is prohibited. .

  Here, the first and second embodiments regarding the change of the opening / closing timing of the intake valve 65 and the start of fuel injection will be further described, including the time chart of FIG. In these embodiments, an example in which in-cylinder direct injection by the in-cylinder injector 11 is started is shown. The lower side of FIG. 4 shows the engine speed and the in-cylinder direct injection timing, and the upper side shows the opening / closing timing including the operating angle of the intake valve 65. FIG. 4 (A) shows the opening / closing timing including the operating angle of the intake valve 65 at the time of steady operation of the engine 1 as the initial position before starting, and FIG. 4 (B) shows the intake valve after the change. FIG. 4C shows the second embodiment of the opening / closing timing and the injection timing of the intake valve 65 after the change, respectively.

  In the first embodiment, the intake valve 65 is opened at about 45 ° after exhaust top dead center (TDC) and closed at about bottom dead center (BDC), whereas in-cylinder injection by the in-cylinder injector 11 is performed. The injection toward the combustion chamber 64 is started immediately before the intake valve 65 is opened. Thus, with the intake valve 65 closed, fuel is injected from the in-cylinder injector 11 onto the top surface of the piston 62 immediately after the start of lowering. At this time, since the negative pressure in the cylinder is large, fine particles of injected fuel are injected. Conversion is performed well. In this state, the intake valve 65 is further opened as the piston 62 is further lowered, so that the mixture in the cylinder is promoted by the aspirating flow into the cylinder, so that the mixture is suitable for ignition by the spark plug 69. Will be formed.

  Further, in the second embodiment, the intake valve 65 is opened at about the exhaust top dead center (TDC) and closed at about 45 ° before the bottom dead center (BDC), whereas the in-cylinder injector 11 is used. Injection toward the combustion chamber 64 in the cylinder is started at the bottom dead center (BDC). Thus, fuel is injected from the in-cylinder injector 11 into the cylinder in the negative pressure growth state after the intake valve 65 is closed, but the piston 62 is at the bottom dead center position. Since the spray can spread into the space without hitting the top surface of the piston 62, atomization or vaporization is promoted with boiling under reduced pressure, and an air-fuel mixture suitable for ignition by the spark plug 69 is formed as in the previous embodiment. Will be.

  Further, as third to fifth embodiments, the change in the opening / closing timing of the intake valve 65 and the exhaust valve 66 and the start of fuel injection will be described with reference to FIG. In these embodiments, an example in which the intake passage injection by the intake passage injection injector 12 is started is shown. FIG. 5 (A) shows the opening / closing timing including the operating angles of the intake valve 65 and the exhaust valve 66 during the steady operation of the engine 1 as the initial position before starting, and FIG. FIG. 5C and FIG. 5D show the opening and closing timings of the intake valve 65 and the exhaust valve 66 after the change in the fourth and fifth embodiments. Timing and injection timing are shown respectively.

  In the third embodiment shown in FIG. 5B, the operating angle of the exhaust valve 66 is not changed, only the intake valve 65 is changed and opened at about 45 ° after exhaust top dead center (TDC). While it is closed at the bottom dead center (BDC), the intake passage injection by the intake passage injection injector 12 is started immediately before the intake valve 65 is opened. Thus, fuel is injected into the intake passage with the intake valve 65 closed, and most of the injected fuel adheres to the wall surface of the intake passage. In this state, since the intake valve 65 is opened as the piston 62 descends, the sudden flow of suction into the cylinder promotes atomization or vaporization of the fuel adhering to the intake passage wall surface, which is suitable for ignition by the ignition plug 69. An air-fuel mixture will be formed.

  Further, in the fourth embodiment shown in FIG. 5C, the opening / closing timing including the operating angle of the exhaust valve 66 is changed so as to be closed at about 30 ° before exhaust top dead center (TDC). 65 is opened at about 45 ° before exhaust top dead center (TDC) and closed at about 15 ° before bottom dead center (BDC), whereas injection in the intake passage by the intake passage injection injector 12 is the intake valve 65. Is started almost simultaneously with the closing of the exhaust valve 66 after opening. Thus, fuel is injected into the intake passage with the intake valve 65 open, and most of the injected fuel adheres to the wall surface of the intake passage. In this state, the piston 62 is moving upward, so Atomization or vaporization is promoted by the reverse flow of the air into the intake passage, that is, the jet flow, and the subsequent suction flow caused by the downward movement of the piston 62, and an air-fuel mixture suitable for ignition by the spark plug 69 is formed. .

  Furthermore, in the fifth embodiment shown in FIG. 5D, the opening / closing timing including the working angle of the exhaust valve 66 is about 30 ° before exhaust top dead center (TDC), as in the fourth embodiment. While the intake valve 65 is changed to be closed, the intake valve 65 is opened at approximately the exhaust top dead center (TDC) and is closed at about 45 ° after the bottom dead center (BDC), whereas the intake air by the intake passage injection injector 12 is changed. In-passage injection begins at approximately top dead center (TDC). Thus, fuel is injected into the intake passage with the intake valve 65 open. In such a state, the exhaust valve 66 of the piston 62 after being closed at about 30 ° before exhaust top dead center (TDC). Ascending, the air compressed in the cylinder becomes a reverse flow, that is, a jet flow into the intake passage, and the atomization or vaporization of the injected fuel is promoted in combination with the suction flow due to the lowering of the piston 62 thereafter, and ignition is performed. An air-fuel mixture suitable for ignition by the plug 69 is formed.

  Here, it is determined in step S301 in the above-described start-up fuel injection control routine whether or not the engine 1 is at start-up. The start-up switch 49 determines whether or not the engine 1 is in start-up. When the engine speed Ne is at the cranking engine speed Nec when the engine is on and after the time t1 when the engine Ne exceeds the predetermined value Ne1 and the engine speed Ne exceeds the predetermined value Ne1. This can be done depending on whether the elapsed time t has exceeded a predetermined value ts (see FIG. 4). The predetermined value Ne1 of the rotational speed is Ne1 = 300 to 400 rpm as a guideline that the complete explosion has been performed, and the predetermined value ts of the elapsed time is ts as the rotational speed increase and stabilization period after the complete explosion. = 1 to 10 seconds, or may depend on whether the cooling water temperature of the engine 1, which is a detection value from the water temperature sensor 38, has reached a predetermined temperature.

  The control of the present invention at the time of starting will be further described with reference to the time chart shown in FIG. 4 again. First, at the time point tc, the starter switch 49 is turned on, cranking by the starter is performed, and target opening / closing is performed. At the time point t0 when the setting to the timing is completed, fuel injection into the cylinder by the in-cylinder injector 11 is started in the first and second embodiments described above. In the third to fifth embodiments, The fuel injection into the intake passage by the intake passage injection injector 12 is started.

  Next, an example of the control at the time of starting of still another embodiment of the present invention will be described below with reference to the flowchart shown in FIG. Since the difference between the embodiment described below and the embodiment already described as the first to fifth embodiments is only the difference in the fuel injection mode, the previous description is used for common parts, and Explain the differences with emphasis and avoid duplicate explanations.

  That is, from step S601 in which it is determined whether or not the engine has been started to step S606 in which it is determined whether or not the setting to the target opening / closing timing has been completed is the same as steps S301 to S306. Do not repeat. Therefore, if it is determined in step S606 that the setting for the target opening / closing timing has not been completed, the routine proceeds to step S308, where fuel injection according to the injection mode 1 is executed. On the other hand, as a result of the determination in step S606, the setting is completed, in other words, when it is changed to the predetermined target opening / closing timing, the process proceeds to step S607, and the fuel injection is changed to the injection mode 2. Note that, when it is not a start time in the determination in step S601, this routine is ended as in the above-described embodiment.

  Here, embodiments of changing the opening / closing timing of the intake valve 65 and changing the fuel injection mode will be further described as sixth and seventh embodiments, including the time chart of FIG. In these embodiments, after the fuel injection into the intake passage or the port by the intake passage injection injector 12 is started and the setting to the target opening / closing timing is completed, the direct injection is changed to the in-cylinder direct injection by the in-cylinder injector 11. An example is shown. The lower side of FIG. 7 shows the engine speed and the timing of intake passage injection or port injection and in-cylinder direct injection, almost the same as in FIG. Including opening / closing timing is shown. FIG. 7 (A) shows the opening / closing timing including the operating angle of the intake valve 65 at the time of steady operation of the engine 1 as the initial position before starting, and FIG. 7 (B) shows the intake valve after the change. FIG. 7C shows a sixth embodiment of the opening / closing timing and injection timing of 65, and FIG. 7C shows the seventh embodiment of the opening / closing timing and injection timing of the intake valve 65 after the change.

  In the sixth embodiment, the intake valve 65 is opened at about 45 ° after exhaust top dead center (TDC) and closed at about bottom dead center (BDC), whereas in-cylinder injection by the in-cylinder injector 11 is performed. The injection toward the combustion chamber 64 is started immediately before the intake valve 65 is opened. In the sixth embodiment, first, at time tc, the starter switch 49 is turned on and cranking by the starter is performed almost simultaneously with the start of fuel injection into the intake passage by the intake passage injector 12. . Then, at the time point t0 when the setting to the target opening / closing timing is completed, the fuel injection is changed into in-cylinder fuel injection by the in-cylinder injector 11.

  Thus, when the intake valve 65 is closed, the fuel injected into the intake passage or the port by the intake passage injection injector 12 causes a certain amount of fuel to preliminarily adhere to the intake passage wall including the port. To do. Immediately before the intake valve 65 is opened, fuel is injected from the in-cylinder injector 11 onto the top surface of the piston 62 after starting to descend, and most of the injected fuel adheres to the top surface of the piston 62. In this state, since the intake valve 65 is opened as the piston 62 descends, atomization or vaporization is accelerated by the aspirating flow of the intake air including the fuel vaporized in the port into the cylinder, and the ignition plug 69 A homogeneous mixture suitable for ignition is formed.

  Also in the seventh embodiment, at the time tc, the starter switch 49 is turned on and cranking by the starter is performed almost simultaneously with the start of the fuel injection into the intake passage by the intake passage injection injector 12. . Then, at the time point t0 when the setting to the target opening / closing timing is completed, the fuel injection is changed into in-cylinder fuel injection by the in-cylinder injector 11. Thus, in a state where the intake valve 65 is closed, a certain amount of fuel is preliminarily attached to the intake passage wall including the port by the fuel injected into the intake passage or the port by the intake passage injection injector 12. . The intake valve 65 is opened at approximately the exhaust top dead center (TDC) and closed at approximately 45 ° before the bottom dead center (BDC), whereas the in-cylinder injector 11 causes the combustion chamber 64 in the cylinder to enter the combustion chamber 64. Injecting towards the bottom dead center (BDC) is started. Thus, fuel is injected from the in-cylinder injector 11 into the cylinder in the negative pressure growth state after the intake valve 65 is closed, but the piston 62 is at the bottom dead center position. Since the spray can spread into the space without hitting the top surface of the piston 62, atomization or vaporization is promoted with boiling under reduced pressure, and in the same manner as in the previous embodiment, it is in phase with the intake air containing fuel vaporized in the port. As a result, a homogeneous mixture suitable for ignition by the spark plug 69 is formed.

  In the embodiment of the present invention described above, an example of changing the fuel injection mode from in-passage fuel injection by the intake-path injection injector 12 to in-cylinder fuel injection by the in-cylinder injector 11 (referred to as a). However, this is a change from the in-cylinder fuel injection to the dual fuel injection by both the in-cylinder injector and the intake passage injector (referred to as b), and from the in-cylinder fuel injection to the dual fuel injection. Change (referred to as “c”), or a change to any one of the fuel injection sources including a change from dual fuel injection to in-cylinder fuel injection (referred to as “d”).

  In addition, the fuel injection mode is changed from fuel injection in the intake passage to fuel injection in the intake passage in which any one of the fuel injection control values including the fuel injection amount, the fuel injection timing, and the sharing ratio is changed before and after the change. Changes (referred to as e), changes from in-cylinder fuel injection to in-cylinder fuel injection (referred to as f), and changes from dual fuel injection to dual fuel injection (referred to as g). May be.

  In both (a) and (b) above, the fuel adhering to the intake passage (port) is preliminarily generated, and the homogenous mixture suitable for ignition is improved by improving the atomization by the increased in-cylinder injection. Can be formed. In both (c) and (f), in-cylinder attached fuel is stably generated preliminarily by intake stroke injection or the like, and the atomization is improved by in-cylinder injection with increased fuel injection timing and ignition. It is possible to form a homogeneous gas mixture suitable for the above. In both (d) and (g), the intake passage (port) adhering fuel and the in-cylinder adhering fuel are stably generated in a preliminary manner, and the atomization is performed by the in-cylinder injection that is increased by changing the sharing ratio. It is possible to improve and form a homogeneous mixture suitable for ignition. Further, (e) shows that the fuel adhering to the intake passage (port) is preliminarily generated by the intake asynchronous injection, and is atomized by the port injection which is increased and changed to the injection timing shown in the third to fifth embodiments. Or the vaporization can be improved and a homogeneous air-fuel mixture suitable for ignition can be formed. In any case, by selecting an optimal change mode that matches the set opening / closing timing of the valve operating system, it is possible to shorten the starting time, improve the fuel consumption, and improve the emission.

  In the above embodiment, only the example of changing the opening / closing timing of the valve operating system has been described, but it goes without saying that this may also change the lift amount.

1 is a schematic diagram showing a schematic configuration diagram of a fuel injection control device for a dual injection internal combustion engine according to the present invention. It is a sectional side view of the engine shown in FIG. It is a flowchart which shows an example of the fuel injection control routine at the time of start in embodiment of this invention. 4 is a time chart at the time of start in an embodiment of the present invention, where (A) is an opening / closing timing including an operating angle of the intake valve as an initial position before starting, and (B) is an opening / closing timing and injection of the intake valve after the change. (C) shows the second embodiment of the opening / closing timing and the injection timing of the intake valve after the change. (A) is an opening / closing timing including the operating angles of the intake valve and the exhaust valve as an initial position before start-up, and (A) shows the opening / closing timing including the operating angles of the intake valve and the exhaust valve in the embodiment of the present invention. (B) is a third embodiment of the opening / closing timing and injection timing of the intake valve and exhaust valve after the change, and (C) and (D are the opening / closing timing and injection timing of the intake valve and exhaust valve after the change. Fourth and fifth embodiments are shown respectively. It is a flowchart which shows the other example of the fuel injection control routine at the time of start in embodiment of this invention. 4 is a time chart at the time of start in an embodiment of the present invention, where (A) is an opening / closing timing including an operating angle of the intake valve as an initial position before starting, and (B) is an opening / closing timing and injection of the intake valve after the change. 6th embodiment with timing, (C) shows 7th embodiment with the opening-and-closing timing and injection timing of the intake valve after a change.

Explanation of symbols

11 Injector for cylinder injection 12 Injector for intake passage injection 30 Electronic control unit 38 Water temperature sensor 44 Accelerator opening sensor 46 Rotation speed sensor 49 Starter switch

Claims (3)

In an internal combustion engine comprising both an in-cylinder injector that injects fuel into a cylinder and an intake-path injector that injects fuel into an intake passage,
Fuel injection mode changing means for changing the fuel injection mode by the in-cylinder injector and the intake passage injector.
And at least valve timing changing means for changing the opening / closing timing of the intake valve,
When the engine is started, the opening / closing timing including at least the operating angle of the intake valve is changed to a predetermined timing by the valve timing changing means, and the fuel injection form is changed to the predetermined timing by the fuel injection form changing means. Will be changed differently after the change,
The change in the fuel injection mode includes in-cylinder fuel injection using only the in-cylinder injector, in-cylinder fuel injection using only the intake passage injector, and both the in-cylinder injector and the intake passage injector. Or any one of the fuel injection control values including the fuel injection amount, the fuel injection timing, and the sharing ratio by the same fuel injection source. Engine fuel injection control device. The change of at least the opening / closing timing of the intake valve by the valve timing changing means is from the opening / closing timing at the time of steady operation to the opening / closing timing at which the intake valve is opened at about 45 ° after exhaust top dead center and is almost closed at bottom dead center. Change,
The change of the fuel injection form by the fuel injection form changing means is the intake valve after the change from the fuel injection in the intake passage by the injector for the intake passage injection before the change to the opening / closing timing to the opening / closing timing. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection mode is changed to in-cylinder fuel injection by the in-cylinder injector at a fuel injection timing immediately before opening. At least the opening / closing timing of the intake valve by the valve timing changing means is changed from the opening / closing timing at the time of steady operation to the opening / closing timing at which the intake valve is opened at about exhaust top dead center and closed at about 45 ° before bottom dead center. Change,
The change of the fuel injection form by the fuel injection form changing means is the bottom dead center after the change from the fuel injection in the intake passage by the intake passage injection injector before the change to the opening / closing timing to the opening / closing timing. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection mode is changed to in-cylinder fuel injection by the in-cylinder injector at a fuel injection timing.

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