JP2005351162A - Fuel injection control method of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the deterioration in emission, by reducing a leakage quantity of fuel from a cylinder fuel injection valve when stopping an internal combustion engine. <P>SOLUTION: This internal combustion engine has the cylinder fuel injection valve and a passage fuel injection valve. The internal combustion engine is stopped after reducing fuel pressure of a pressure accumulating part (S105) by injecting the fuel by both the cylinder fuel injection valve and the passage fuel injection valve (S102 and S103) in a state of stopping supply of the fuel or reducing a quantity to the pressure accumulating part for sending the fuel into the cylinder fuel injection valve when stopping the internal combustion engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection control method for an internal combustion engine, and more particularly, to a fuel injection control method for an internal combustion engine including an in-cylinder fuel injection valve that injects fuel into a cylinder and a passage fuel injection valve that injects fuel into an intake passage. About.

  In an internal combustion engine having an in-cylinder fuel injection valve that injects fuel into a cylinder, a technique is known in which a decompression passage is provided between a fuel supply passage for supplying fuel to the fuel injection valve and a drain passage (for example, Patent Document 1). In such an internal combustion engine, when the internal combustion engine is stopped after warming up, the fuel accumulated in the in-cylinder fuel injection valve is volume-expanded by the heat of the internal combustion engine, and the internal pressure becomes high, The pressure reducing passage is opened to reduce the pressure inside the cylinder fuel injection valve.

Further, in an internal combustion engine, fuel supplied from a fuel tank is temporarily accumulated in a pressure accumulating portion and accumulated, and fuel is injected from the pressure accumulating portion to a fuel injection valve. In an internal combustion engine having an in-cylinder fuel injection valve that injects fuel into the cylinder and a passage fuel injection valve that injects fuel into the intake passage, the in-cylinder fuel injection valve and the passage fuel injection valve accumulate pressure separately. Department is installed. In this case, in general, the fuel injection pressure from the in-cylinder fuel injection valve needs to be higher than the fuel injection pressure from the passage fuel injection valve. The pressure is higher than the fuel pressure of the pressure accumulator on the valve side.
JP-A-2-119669 JP-A-7-103048 JP 2001-342876 A Japanese Patent Laid-Open No. 2002-4985

  In an internal combustion engine, fuel may leak from the fuel injection valve even when the operation of the internal combustion engine is stopped, that is, when fuel injection by the fuel injection valve is not performed. This is because the fuel is stored in a high pressure state in the pressure accumulating portion that sends the fuel to the fuel injection valve. The higher the fuel pressure in the pressure accumulating portion, the greater the amount of fuel leakage from the fuel injection valve. If the amount of fuel leaking from the fuel injection valve increases while the internal combustion engine is stopped, there is a possibility that the emission at the next start of the internal combustion engine may be deteriorated.

  Here, in the internal combustion engine including the in-cylinder fuel injection valve and the passage fuel injection valve, the fuel pressure of the pressure accumulating portion on the cylinder fuel injection valve side becomes higher than the fuel pressure of the pressure accumulating portion on the passage fuel injection valve side. Yes. Furthermore, since the cylinder fuel injection valve is located closer to the combustion chamber than the port fuel injection valve, the temperature is likely to be higher. Therefore, fuel is more likely to leak from the in-cylinder fuel injection valve than the passage fuel injection valve.

  The present invention has been made in view of the above problems, and in an internal combustion engine having an in-cylinder fuel injection valve and a passage fuel injection valve, fuel leakage from the in-cylinder fuel injection valve while the internal combustion engine is stopped. It is an object of the present invention to provide a technique capable of suppressing the deterioration of emission by reducing the amount.

The present invention relates to an internal combustion engine having an in-cylinder fuel injection valve and a passage fuel injection valve. When the internal combustion engine is stopped, the supply of fuel to a pressure accumulating unit that sends fuel to the in-cylinder fuel injection valve is stopped or reduced. In this state, fuel injection is performed by both the in-cylinder fuel injection valve and the passage fuel injection valve, thereby reducing the fuel pressure in the pressure accumulating section and then stopping the internal combustion engine.

More specifically, the fuel injection control method for an internal combustion engine according to the present invention includes:
An in-cylinder fuel injection valve for injecting fuel into the cylinder;
A passage fuel injection valve for injecting fuel into the intake passage;
An accumulator for accumulating and accumulating the supplied fuel and then sending the fuel to the in-cylinder fuel injection valve;
When the stop condition of the internal combustion engine is satisfied, the supply of fuel to the pressure accumulator is stopped or reduced, and fuel is injected and injected by both the in-cylinder fuel injection valve and the passage fuel injection valve. The fuel is burned in the cylinder, and then fuel injection by the in-cylinder fuel injection valve and the passage fuel injection valve is stopped when a predetermined time has elapsed.

  According to the present invention, when the internal combustion engine is stopped, the fuel is injected from the in-cylinder fuel injection valve for a specified time in a state where the supply of fuel to the pressure accumulator is stopped or reduced before the stop. Therefore, the fuel pressure in the pressure accumulator gradually decreases until the specified time elapses, and when the internal combustion engine is actually stopped, the fuel pressure in the pressure accumulator is greater than when the internal combustion engine stop condition is satisfied. Is reduced. That is, the fuel pressure of the pressure accumulating portion when the internal combustion engine is stopped can be further reduced. As a result, it is possible to reduce the amount of fuel leakage from the in-cylinder fuel injection valve while the internal combustion engine is stopped, thereby suppressing the deterioration of emissions.

  In the present invention, fuel injection is performed not only by the in-cylinder fuel injection valve but also by the passage fuel injection valve from when the internal combustion engine stop condition is satisfied until the specified time elapses. The pressure accumulating unit according to the present invention feeds fuel only to the in-cylinder fuel injection valve, and is independent of the passage fuel injection valve. Therefore, the fuel pressure of the pressure accumulator decreases until the specified time elapses, so that the fuel injection amount from the in-cylinder fuel injection valve becomes unstable or the fuel injected from the in-cylinder fuel injection valve Even when the atomization deteriorates, stable combustion can be performed by fuel injection by the passage fuel injection valve.

  In the present invention, the stop condition of the internal combustion engine may be, for example, an ignition OFF by the driver, or an automatic stop condition of the internal combustion engine in an economy running system or a hybrid system.

  In the present invention, the specified time is a time that is within an allowable range from when the internal combustion engine stop condition is satisfied until the internal combustion engine actually stops, and may be a predetermined time. In addition, even when the in-cylinder fuel injection valve is in the open state, the fuel pressure in the pressure accumulating unit may be reduced to a target fuel pressure that is a fuel pressure at which fuel is not injected from the in-cylinder fuel injection valve.

  In this case, since the fuel pressure of the pressure accumulating unit when the internal combustion engine is stopped can be made equal to or lower than the target fuel pressure, the amount of fuel leakage from the in-cylinder fuel injection valve when the internal combustion engine is stopped can be further reduced.

Further, in the present invention, when the internal combustion engine is provided with an exhaust purification catalyst in the exhaust passage, and the specified time is the first specified time, the in-cylinder fuel is When the fuel pressure in the accumulator does not drop below the target fuel pressure, which is the fuel pressure at which fuel is not injected from the in-cylinder fuel injector, even when the injector is open, the time when the first specified time has elapsed Then, only the fuel injection by the passage fuel injection valve may be stopped, and the fuel injection by the in-cylinder fuel injection valve may be further continued for the second specified time. In this case, the fuel injected by the in-cylinder fuel injection valve is prevented from burning in the cylinder after the first specified time has elapsed and before the second specified time has elapsed.

  According to such control, after the stop condition of the internal combustion engine is established, that is, after the fuel injection by the in-cylinder fuel injection valve in the state where the supply of fuel to the pressure accumulating portion is stopped, the first is performed. When the specified time elapses, if the fuel pressure in the pressure accumulator does not decrease to the target fuel pressure, the fuel pressure in the pressure accumulator can be further reduced. Therefore, the fuel pressure of the pressure accumulating unit can be lowered while the internal combustion engine is stopped, and as a result, the amount of fuel leakage from the in-cylinder fuel injection valve while the internal combustion engine is stopped can be further reduced.

  In the above case, the first specified time can be set to a shorter time than when the first specified time is set to a time during which the fuel pressure of the pressure accumulating unit is reduced to the target fuel pressure or less. That is, the fuel injection by the passage fuel injection valve can be stopped earlier. Therefore, it is possible to suppress a reduction in fuel consumption more than in the case where port fuel injection is performed until the fuel pressure in the pressure accumulator decreases below the target fuel pressure after the stop condition for the internal combustion engine is established.

  Note that, by the above control, after the first specified time has elapsed, the fuel injection by the passage fuel injection valve is stopped and the fuel is not burned even if the fuel injection by the in-cylinder fuel injection valve is performed. Even so, the internal combustion engine has been operating for some time due to inertia. Therefore, the fuel injected by the in-cylinder fuel injection valve is mixed with air without being combusted and discharged into the exhaust passage while the second specified time elapses. Immediately after the first specified time elapses, the exhaust purification catalyst installed in the exhaust passage is still activated, so that unburned fuel discharged into the exhaust passage is purified by the exhaust purification catalyst. Is done. Therefore, even if the fuel is injected by the in-cylinder fuel injection valve until the second specified time elapses after the first specified time elapses, the fuel injected at this time causes the deterioration of the emission. The chance of inviting is small.

  Further, since the fuel injected by the in-cylinder fuel injection valve is not combusted in the cylinder until the second specified time elapses, no torque is generated. Therefore, the possibility that the time until the internal combustion engine actually stops is further extended.

  In the control as described above, the second specified time may be a time during which the rotation speed of the internal combustion engine becomes the specified rotation speed.

  In this case, the specified rotational speed is a predetermined rotational speed, the fuel injected from the in-cylinder fuel injection valve is mixed with air and discharged to the exhaust passage, and the discharged air-fuel mixture is the exhaust purification catalyst. It is preferable to set the rotation speed within a range that can easily be purified.

  In the control as described above, when the fuel is injected by the in-cylinder fuel injection valve after the first specified time elapses and before the second specified time elapses, the first specified time elapses. It is preferable to make the opening time of the in-cylinder fuel injection valve longer for each fuel injection than when injecting fuel with the in-cylinder fuel injection valve.

  According to such control of the opening time of the in-cylinder fuel injection valve, more fuel can be injected from the in-cylinder fuel injection valve until the second specified time elapses. As a result, the fuel pressure of the pressure accumulator can be further reduced.

  Further, when fuel is injected by the in-cylinder fuel injection valve after the first specified time has elapsed and before the second specified time has elapsed, the fuel injection is executed at the timing when the cylinder is in the expansion stroke or the exhaust stroke. You may do it. By setting the timing of fuel injection by the in-cylinder fuel injection valve to such a timing, the fuel injected from the in-cylinder fuel injection valve is easily discharged through the exhaust passage.

  According to the fuel injection control method for an internal combustion engine according to the present invention, in the internal combustion engine having the in-cylinder fuel injection valve and the passage fuel injection valve, the amount of fuel leakage from the in-cylinder fuel injection valve while the internal combustion engine is stopped. Therefore, it is possible to suppress the deterioration of emission.

  Embodiments of a fuel injection control method for an internal combustion engine according to the present invention will be described below with reference to the drawings.

<Schematic configuration of internal combustion engine and its fuel supply system>
First, a first embodiment of a fuel injection control method for an internal combustion engine according to the present invention will be described. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its fuel supply system according to the present embodiment. The internal combustion engine 1 is a four-cylinder gasoline engine having four cylinders 2. A piston 3 is slidably provided in each cylinder 2. An intake port 4 and an exhaust port 5 are connected to the combustion chamber in the upper part of the cylinder 2. The openings of the intake port 4 and the exhaust port 5 to the combustion chamber are opened and closed by an intake valve 6 and an exhaust valve 7, respectively. The intake port 4 and the exhaust port 5 are connected to an intake passage 8 and an exhaust passage 9, respectively. An exhaust gas purification catalyst 23 that purifies unburned components discharged from the internal combustion engine 1 is installed in the exhaust passage 9.

  Further, the internal combustion engine 1 is provided with an in-cylinder fuel injection valve 10 for injecting fuel into the cylinder 2 and a port fuel injection valve 11 for injecting fuel into the intake port 4 toward the opening to the combustion chamber. ing. Further, an ignition plug 18 for igniting an air-fuel mixture that flows into the combustion chamber or is formed in the combustion chamber is provided in the combustion chamber in the upper part of the cylinder 2.

  The internal combustion engine 1 is provided with a fuel tank 19. One end of the first fuel supply path 14 is inserted into the fuel tank 19, and the other end of the first fuel supply path 14 is connected to the first delivery pipe 12. One end of the second fuel supply path 15 is connected to the middle of the first fuel supply path 14, and the other end of the second fuel supply path 15 is connected to the second delivery pipe 13. The first delivery pipe 12 and the second delivery pipe 13 store fuel and accumulate pressure, respectively, and then send the fuel to the in-cylinder fuel injection valve 10 and the port fuel injection valve 11.

  The fuel is pumped from the fuel tank 19 side to the first delivery pipe 12 and the second delivery pipe 13 side on the upstream side (fuel tank 19 side) of the first fuel supply path 14 connected to the second fuel supply path 15. A first fuel pump 16 is installed. Further, the first fuel supply path 14 is connected to the second fuel supply path 15 on the downstream side (first delivery pipe 12 side), and fuel is pumped from the fuel tank 19 side to the first delivery pipe 12 side. Two fuel pumps 17 are installed. Further, a fuel flow rate control valve 24 for controlling the amount of fuel flowing into the second fuel pump 17 is provided between the connection portion of the first fuel supply passage 14 with the second fuel supply passage 15 and the second fuel pump 17. is set up.

  Further, the first delivery pipe 12 is provided with a fuel pressure sensor 21 that outputs an electrical signal corresponding to the fuel pressure in the delivery pipe 12. Further, the internal combustion engine 1 is provided with a crank position sensor 22 that outputs an electrical signal corresponding to a crank angle of a crankshaft connected to the piston 3 via a connecting rod.

The internal combustion engine 1 configured as described above is provided with an ECU 20 for controlling the internal combustion engine 1. The ECU 20 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. Various sensors such as a fuel pressure sensor 21 and a crank position sensor 22 are connected to the ECU 20 via electric wiring, and these output signals are input to the ECU 20.

  Further, the in-cylinder fuel injection valve 10, the port fuel injection valve 11, the spark plug 18, the first fuel pump 16, the second fuel pump 17, and the fuel flow control valve 24 are electrically connected to the ECU 20. These are controlled by the ECU 20. During operation of the internal combustion engine 1, more fuel than the second delivery pipe 13 is supplied to the first delivery pipe 12 by the second fuel pump 17 in addition to the first fuel pump 16. The fuel pressure is controlled to be higher than the fuel pressure in the second delivery pipe 13.

<Fuel injection control 1 when the engine is stopped>
Here, the fuel injection control when stopping the internal combustion engine 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing a fuel injection control routine when the internal combustion engine 1 is stopped. This routine is stored in advance in the ECU 20 and is repeated every specified execution time.

  In this routine, the ECU 20 first determines in S101 whether or not a stop condition for the internal combustion engine 1 is satisfied. Here, examples of the stop condition of the internal combustion engine 1 include ignition OFF by the driver. Moreover, when the internal combustion engine 1 is applied to an economy running system or a hybrid system, the stop condition may be an automatic stop condition in these systems. If an affirmative determination is made in S101, the ECU 20 proceeds to S102, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S102, the ECU 20 stops the fuel supply to the first delivery pipe 12 by stopping the second fuel pump 17 and closing the fuel flow rate control valve 24.

  Next, the ECU 20 proceeds to S103, performs in-cylinder fuel injection by the in-cylinder fuel injection valve 10 and port fuel injection by the port fuel injection valve 11, and executes ignition of the air-fuel mixture by the spark plug 18. After S103, in-cylinder fuel injection is performed in a state where the supply of fuel to the first delivery pipe 12 is stopped, so that the fuel pressure in the first delivery pipe 12 gradually decreases.

  Next, the ECU 20 proceeds to S104, and determines whether or not a specified time has elapsed since the start of in-cylinder fuel injection and port fuel injection in S103. The specified time here is a time that is within a permissible time from when the stop condition of the internal combustion engine 1 is established until the internal combustion engine 1 actually stops, and is a predetermined time. If an affirmative determination is made in S104, the ECU 20 proceeds to S105, and if a negative determination is made, the ECU 20 repeats S104.

  In step S105, the ECU 20 stops in-cylinder fuel injection, in-port fuel injection, and ignition by the spark plug 18, and ends the execution of this routine.

  According to the present embodiment, when the internal combustion engine 1 is stopped, the fuel is injected from the in-cylinder fuel injection valve 10 for a specified time in a state where the supply of fuel to the first delivery pipe 12 is stopped before the stop. . Therefore, the fuel pressure in the first delivery pipe 12 gradually decreases until the specified time elapses, and when the internal combustion engine 1 is actually stopped, the stop condition of the internal combustion engine 1 is established. Rather, the fuel pressure in the first delivery pipe 12 is reduced. That is, the fuel pressure in the first delivery pipe 12 when the internal combustion engine 1 is stopped can be further reduced. As a result, it is possible to reduce the amount of fuel leakage from the in-cylinder fuel injection valve 10 when the internal combustion engine 1 is stopped, thereby suppressing the deterioration of emissions.

  Further, in the present embodiment, fuel injection is performed not only by the in-cylinder fuel injection valve 10 but also by the port fuel injection valve 11 until the specified time elapses after the stop condition of the internal combustion engine 1 is established. . Therefore, the fuel pressure in the first delivery pipe 12 decreases until the specified time elapses, so that the fuel injection amount from the in-cylinder fuel injection valve 10 becomes unstable, or the in-cylinder fuel injection valve 10 Even when the atomization of the fuel injected from the fuel is deteriorated, stable combustion can be performed by the fuel injection by the port fuel injection valve 11.

  In this embodiment, in S102 of the fuel injection control routine, the first delivery pipe is reduced by reducing the pressure of fuel pumped by the second fuel pump 17 or by reducing the opening of the fuel flow control valve 24. The fuel supply to 12 may be reduced. Such control can also lower the fuel pressure in the first delivery pipe 12 when the internal combustion engine 1 is stopped.

  Next, a second embodiment of the fuel injection control method for an internal combustion engine according to the present invention will be described. Since the schematic configuration of the internal combustion engine and its fuel supply system according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

<Fuel injection control 2 when the engine is stopped>
Here, the fuel injection control when stopping the internal combustion engine 1 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a fuel injection control routine when the internal combustion engine 1 is stopped. Note that S201 to S203 and S205 in this routine are the same as S101 to S103 and S105 in the fuel injection control routine shown in FIG. Therefore, only S204 will be described here. Further, this routine is also a routine that is stored in the ECU 20 in advance and is repeated every specified execution time, as described above.

  In this routine, the ECU 20 performs in-cylinder fuel injection and port fuel injection in S203, and then proceeds to S204.

  In S204, the ECU 20 determines whether or not the fuel pressure in the first delivery pipe 12 has dropped below the target fuel pressure. The target fuel pressure here is a fuel pressure at which fuel is not injected from the in-cylinder fuel injection valve 10 even when the in-cylinder fuel injection valve 10 is in the open state. If an affirmative determination is made in S204, the ECU 20 proceeds to S205, and if a negative determination is made, the ECU 20 repeats S204.

  According to the present embodiment, the fuel pressure in the first delivery pipe 12 during the stop of the internal combustion engine 1 can be made equal to or lower than the target fuel pressure, so that the fuel from the in-cylinder fuel injection valve 10 during the stop of the internal combustion engine 1 can be reduced. The amount of leakage can be further reduced.

  Next, a third embodiment of the fuel injection control method for an internal combustion engine according to the present invention will be described. Since the schematic configuration of the internal combustion engine and its fuel supply system according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

<Fuel injection control 3 when the engine is stopped>
Here, fuel injection control when the internal combustion engine 1 is stopped according to the present embodiment will be described with reference to FIGS. 4 and 5 are flowcharts showing a fuel injection control routine when the internal combustion engine 1 is stopped. In this routine, S301 to S30.
4 and S306 are the same as S101 to S105 in the fuel injection control routine shown in FIG. Therefore, only S305 and S307 to S311 will be described here. Further, this routine is also a routine that is stored in the ECU 20 in advance and is repeated every specified execution time, as described above.

  In this routine, if an affirmative determination is made in S304, the ECU 20 proceeds to S305.

  In S305, the ECU 20 determines whether or not the fuel pressure in the first delivery pipe 12 has dropped below the target fuel pressure. The target fuel pressure here is a fuel pressure at which fuel is not injected from the in-cylinder fuel injection valve 10 even when the in-cylinder fuel injection valve 10 is in the open state. If an affirmative determination is made in S305, the ECU 20 proceeds to S306, and if a negative determination is made, the ECU 20 proceeds to S307.

  In S307, the ECU 20 stops only the port fuel injection and continues the in-cylinder fuel injection.

  Next, the ECU 20 proceeds to S308, and stops ignition of the air-fuel mixture by the spark plug 18. As a result, even when fuel is injected from the in-cylinder fuel injection valve 10, this fuel does not burn in the cylinder 2 (combustion chamber). Accordingly, since no torque is generated, the internal combustion engine 1 only operates with inertia, and the engine speed gradually decreases.

  Next, the ECU 20 proceeds to S309 and sets the opening time for each fuel injection of the in-cylinder fuel injection valve 10 to the opening time for each fuel injection of the in-cylinder fuel injection valve 10 until the specified time elapses. Longer than. That is, when in-cylinder fuel injection is executed, the in-cylinder fuel injection valve 10 is opened every cycle, and fuel is injected from the in-cylinder fuel injection valve 10, and fuel is injected every cycle. The valve opening time is set longer after the specified time has elapsed than until the specified time has elapsed.

  Next, the ECU 20 proceeds to S310 and determines whether or not the engine speed of the internal combustion engine 1 calculated based on the output signal from the crank position sensor 22 has become equal to or less than a specified speed. The specified rotational speed here means that the fuel injected from the in-cylinder fuel injection valve 10 is mixed with air and discharged to the exhaust passage 9, and the discharged mixture reaches the exhaust purification catalyst 23 and is easily purified. The number of rotations within the range, which is a predetermined number of rotations. If an affirmative determination is made in S310, the ECU 20 proceeds to S311. If a negative determination is made, the ECU 20 repeats S310.

  In step S311, the ECU 20 stops in-cylinder fuel injection and ends the execution of this routine.

  According to the present embodiment, when the specified time has elapsed after the fuel injection by the in-cylinder fuel injection valve 10 in the state where the supply of fuel to the first delivery pipe 12 is stopped, the first delivery pipe When the fuel pressure in 12 has not decreased to the target fuel pressure, the fuel pressure in the first delivery pipe 12 can be further reduced after the lapse of the specified time. Accordingly, the fuel pressure in the first delivery pipe 12 when the internal combustion engine 1 is stopped can be further reduced, and as a result, the amount of fuel leakage from the in-cylinder fuel injection valve 10 when the internal combustion engine 1 is stopped is further reduced. It becomes possible to do.

Further, according to the present embodiment, as in the above-described second embodiment, after the stop condition of the internal combustion engine 1 is established, the in-cylinder fuel injection and the port are performed until the fuel pressure in the first delivery pipe 12 decreases to the target fuel pressure. The port fuel injection can be stopped earlier than when both the fuel injection and the fuel injection are continued. For this reason, it is possible to suppress a reduction in fuel consumption.

  The fuel injected from the in-cylinder fuel injection valve 10 after the lapse of the specified time is not burned in the cylinder 2 (combustion chamber), but is mixed with air and discharged into the exhaust passage 9 by the operation of the internal combustion engine 1 due to inertia. . Immediately after the lapse of the specified time, the exhaust purification catalyst 23 is still activated, so that unburned fuel discharged to the exhaust passage 9 is purified by the exhaust purification catalyst 23. Therefore, in this embodiment, there is little possibility that the emission of fuel will be deteriorated by the fuel injected from the in-cylinder fuel injection valve 10 after the lapse of the specified time.

  Further, even if fuel is injected by the in-cylinder fuel injection valve 10 after the lapse of the specified time, this fuel is not burned in the cylinder 2 and does not generate torque, so the time until the internal combustion engine 1 actually stops. Is less likely to be extended.

  Furthermore, in this embodiment, when fuel is injected by the in-cylinder fuel injection valve 10 after the lapse of the specified time, the fuel is injected more than when fuel is injected by the in-cylinder fuel injection valve 10 until the specified time has elapsed. The valve opening time for each injection is lengthened. By controlling the opening degree of the in-cylinder fuel injection valve 10 in this way, more fuel is injected from the in-cylinder fuel injection valve 10 until the in-cylinder fuel injection is stopped after the lapse of the specified time. I can do it. As a result, the fuel pressure in the first delivery pipe 12 can be further reduced.

  Further, the in-cylinder fuel injection after the lapse of the specified time may be executed at a timing when the cylinder 2 is in the expansion stroke or the exhaust stroke. By setting the in-cylinder fuel injection timing to such a timing, the fuel injected from the in-cylinder fuel injection valve 10 is easily discharged through the exhaust passage 9.

The figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its fuel supply system. The flowchart figure which shows the fuel-injection control routine when stopping an internal combustion engine based on Example 1 of this invention. The flowchart figure which shows the fuel-injection control routine when stopping an internal combustion engine based on Example 2 of this invention. The flowchart figure which shows a part of fuel-injection control routine when stopping an internal combustion engine based on Example 3 of this invention. The flowchart figure which shows a part of fuel-injection control routine when stopping an internal combustion engine based on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 4 ... Intake port 10 ... In-cylinder fuel injection valve 11 ... Port fuel injection valve 12 ... First delivery pipe 13 ... Second delivery pipe 14 ... 1 fuel supply path 15 .. second fuel supply path 16 .. first fuel pump 17 .. second fuel pump 18 .. spark plug 20 .. ECU
21 .. Fuel pressure sensor 22 .. Crank position sensor 23 .. Exhaust purification catalyst 24 .. Fuel flow control valve

Claims (5)

An in-cylinder fuel injection valve for injecting fuel into the cylinder;
A passage fuel injection valve for injecting fuel into the intake passage;
An accumulator for accumulating and accumulating the supplied fuel and then sending the fuel to the in-cylinder fuel injection valve;
When the stop condition of the internal combustion engine is satisfied, the supply of fuel to the pressure accumulator is stopped or reduced, and fuel is injected and injected by both the in-cylinder fuel injection valve and the passage fuel injection valve. A fuel injection control method for an internal combustion engine, wherein fuel is combusted in the cylinder, and then fuel injection by the in-cylinder fuel injection valve and the passage fuel injection valve is stopped when a predetermined time has elapsed.   The specified time is a time during which the fuel pressure of the pressure accumulating section is reduced to a target fuel pressure that is a fuel pressure at which fuel is not injected from the in-cylinder fuel injection valve even when the in-cylinder fuel injection valve is open. The fuel injection control method for an internal combustion engine according to claim 1. The internal combustion engine is provided with an exhaust purification catalyst in the exhaust passage,
A fuel pressure at which fuel is not injected from the in-cylinder fuel injection valve even when the in-cylinder fuel injection valve is open when the first specified time has elapsed, with the specified time being the first specified time. When the fuel pressure of the pressure accumulating portion has not decreased below a certain target fuel pressure, when the first specified time has elapsed, only fuel injection by the passage fuel injection valve is stopped, and by the in-cylinder fuel injection valve Continue fuel injection for a second specified time,
The fuel injected by the in-cylinder fuel injection valve is not combusted in the cylinder until the second specified time elapses after the first specified time elapses. A fuel injection control method for an internal combustion engine as described.   4. The fuel injection control method for an internal combustion engine according to claim 3, wherein the second specified time is a time for which the rotation speed of the internal combustion engine becomes a specified rotation speed.   When fuel is injected by the in-cylinder fuel injection valve after the first specified time elapses and before the second specified time elapses, the fuel is injected before the first specified time elapses. 4. The fuel injection control method for an internal combustion engine according to claim 3, wherein the opening time of the in-cylinder fuel injection valve for each fuel injection is made longer than when fuel is injected by the in-cylinder fuel injection valve.

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