JP5270127B2 - Internal combustion engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for minimizing exhaust emission at cold time, in a system for controlling a spark ignition type internal combustion engine having a fuel injection valve for directly injecting fuel into a cylinder. <P>SOLUTION: This invention is a control system of the spark ignition type internal combustion engine having the fuel injection valve for directly injecting the fuel into the cylinder, When the internal combustion engine is cold, the ignition timing of a spark plug is excessively advanced forward more than MBT, and the injection timing of the fuel injection valve is adjusted so that a combustible air-fuel mixture gathers in the vicinity of the spark plug at an excessively advanced ignition timing. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a control system for a spark ignition internal combustion engine provided with a fuel injection valve that directly injects fuel into a cylinder.

In a spark ignition internal combustion engine having a fuel injection valve that directly injects fuel into a cylinder, fuel injection (hereinafter referred to as “compression stroke injection”) is performed during a compression stroke immediately after a cold start, and compression top dead center Techniques for performing ignition have been proposed (see, for example, Patent Document 1).
JP 2006-112328 A JP-A-4-183924 JP 2000-240547 A

  The present invention relates to a system for controlling a spark ignition internal combustion engine having a fuel injection valve that directly injects fuel into a cylinder, under a condition in which unburned components discharged from the cylinder increase in a cold state or the like. An object of the present invention is to provide a technique for reducing exhaust emission of an internal combustion engine as much as possible.

  In order to solve the above-described problems, the present invention provides a spark ignition type internal combustion engine control system including a fuel injection valve that directly injects fuel into a cylinder. The fuel injection valve timing is adjusted so that the combustible air-fuel mixture is gathered in the vicinity of the spark plug at the ignition timing that is over-advanced.

  When the temperature in the cylinder (hereinafter referred to as “in-cylinder temperature”) is low, such as when the internal combustion engine is cold, the fuel tends to adhere to the inner wall surface of the cylinder and the piston. Most of the fuel adhering to the inner wall surface of the cylinder and the piston (hereinafter referred to as “in-cylinder attached fuel”) is discharged from the cylinder without being burned without being used for combustion. At this time, if the catalyst disposed in the exhaust system of the internal combustion engine is in an inactive state, the unburned components described above are released into the atmosphere without being purified by the catalyst.

  In particular, when the internal combustion engine is started at a low temperature, the period from the start of the internal combustion engine to the activation of the catalyst becomes longer and the amount of in-cylinder attached fuel increases, so that unburned components released into the atmosphere There is concern that the amount of HC, smoke, PM, etc. will be excessive.

  On the other hand, as a result of intensive experiments and verifications by the inventor of the present application, when the ignition timing is advanced to the front of MBT (hereinafter referred to as “over-advanced angle”) in a spark ignition internal combustion engine, the cylinder It has been found that the unburned components discharged from within are significantly reduced.

  This is because when the ignition timing is over-advanced, the amount of the air-fuel mixture that burns before compression top dead center increases, so that the pressure increase / temperature increase effect due to the combustion of the air-fuel mixture is In addition to the temperature effect, the pressure in the cylinder (hereinafter referred to as “in-cylinder pressure”) and the peak of the in-cylinder temperature are increased, and the fuel adhering in the cylinder and / or the fuel before adhering in the cylinder is vaporized and This is thought to be due to the promotion of oxidation.

By the way, in an internal combustion engine provided with a fuel injection valve that directly injects fuel into a cylinder, if the ignition timing is excessively advanced, the above-described effect of the excessively advanced angle may not be sufficiently obtained. For example, if the ignition timing is over-advanced when the internal combustion engine is in a homogeneous combustion operation (operation in which ignition and combustion are performed in a state where fuel and intake air are homogeneously mixed), before the fuel and intake air are uniformly mixed Since ignition is performed, fuel ignition failure and misfire may occur.

  In contrast, the control system for an internal combustion engine according to the present invention sets the injection timing of the fuel injection valve during the compression stroke when the ignition timing is over-advanced, thereby allowing the internal combustion engine to perform stratified combustion operation (cylinder The gas is ignited and burned in a state where the gas is stratified into a layer having a high fuel concentration and a layer having a very low fuel concentration (substantially equal to air).

  Specifically, an internal combustion engine control system according to the present invention includes a fuel injection valve that injects fuel into a cylinder of the internal combustion engine, a spark plug that causes a spark in the cylinder, and an ignition timing of the spark plug by MBT. When the ignition timing is over-advanced before MBT by the over-advance angle means for over-advancing ahead of time, the fuel injection is performed so that the combustion mode of the internal combustion engine is stratified combustion Setting means for setting the injection timing of the valve during the compression stroke.

  According to this invention, it is possible to reduce unburned components discharged from the cylinder while preventing the occurrence of poor fuel ignition and misfiring when the internal combustion engine is cold.

  The setting means according to the present invention sets the injection timing of the fuel injection valve so that the ignition timing over-advanced by the over-advance angle means and the timing when the combustible air-fuel mixture gathers in the vicinity of the spark plug are synchronized. Is preferred.

  When the injection timing of the fuel injection valve is set by such a method, when the ignition timing is over-advanced, reliable ignition of fuel can be promoted.

  As a specific method for setting the injection timing, the injection timing is determined based on the moving speed of fuel injected from the fuel injection valve (hereinafter referred to as “injected fuel”) and the state of the swirling flow generated in the cylinder. A method of setting can be exemplified.

  The timing at which the combustible air-fuel mixture reaches the vicinity of the spark plug becomes earlier as the strength of the swirling flow generated in the cylinder (for example, the number of times the swirling flow swirls per one rotation of the crankshaft) increases. In addition, the timing at which the combustible air-fuel mixture reaches the vicinity of the spark plug becomes earlier as the moving speed of the injected fuel increases.

  Therefore, the injection timing at the time of over-advance may be delayed as the swirl flow generated in the cylinder becomes stronger and / or the moving speed of the injected fuel becomes faster. In other words, the injection timing at the excessive advance angle may be advanced as the swirl flow generated in the cylinder becomes weaker and / or the moving speed of the injected fuel becomes slower.

  As the swirl flow generated in the cylinder, a tumble flow and a swirl flow can be exemplified. In that case, a tumble ratio (the number of times the tumble flow turns per crankshaft rotation) and a swirl ratio (the number of times the swirl flow turns per crankshaft rotation) can be used as a value indicating the strength of the swirling flow. it can. Further, the fuel injection pressure can be used as a value correlated with the moving speed of the injected fuel.

  By the way, when the swirl flow is weak or the moving speed of the injected fuel is slow, the timing at which the combustible mixture reaches the vicinity of the spark plug is delayed, and therefore the injection timing needs to be set early.

  However, if the injection timing is set too early, the convergence of the swirling flow may be reduced before the fuel injection reaches the vicinity of the spark plug. That is, the injected fuel may be diffused and dispersed in the cylinder before reaching the vicinity of the spark plug.

  If the injected fuel is dispersed and diffused before reaching the vicinity of the spark plug, there is a possibility that a combustible air-fuel mixture layer is not formed near the spark plug. That is, since the injected fuel is dispersed over a wide range in the cylinder, the fuel concentration near the spark plug may become excessively thin. As a result, the ignitability and combustion stability of the fuel may be reduced.

  Therefore, the control system for an internal combustion engine according to the present invention further includes control means for enhancing the swirl flow and / or increasing the moving speed of the injected fuel when the injection timing set by the setting means is earlier than a predetermined timing. You may make it prepare.

  When the swirl flow is enhanced by the control means and / or the moving speed of the injected fuel is increased, the convergence property of the swirl flow is improved. For this reason, the injected fuel is not dispersed or diffused before reaching the vicinity of the spark plug. As a result, a combustible mixture layer can be formed in the vicinity of the spark plug.

  If the swirl flow is enhanced and / or the moving speed of the injected fuel is increased, the timing at which the injected fuel reaches the vicinity of the spark plug is advanced. Therefore, it is desirable for the setting means to reset the injection timing based on the strength of the swirling flow after strengthening and / or the moving speed of the injected fuel after increasing.

  As a method for strengthening the swirling flow, a method of using a generating means for generating a swirling flow in the cylinder can be exemplified. Examples of the generating means include an airflow control valve disposed in an intake passage of the internal combustion engine, a variable valve mechanism that changes a valve opening characteristic of the intake valve of the internal combustion engine, and the like.

  When the generating means is an airflow control valve, the control means can reinforce the swirl flow by decreasing the opening degree of the airflow control valve. When the generating means is a variable valve mechanism, the control means can reinforce the swirl flow by retarding the opening timing of the intake valve and / or decreasing the lift amount of the intake valve.

  As a method of increasing the moving speed of the injected fuel, a method of increasing the fuel injection pressure can be exemplified. As a specific method for increasing the fuel injection pressure, a method for increasing the discharge pressure of the fuel pump can be exemplified.

  Next, the control system for an internal combustion engine according to the present invention gradually shifts the injection timing from the previous injection timing to the new injection timing when the actual injection timing is changed according to the injection timing set by the setting means. Alternatively, a transition unit that gradually decreases the injection amount at the previous injection timing and gradually increases the injection amount at the new injection timing may be further provided.

  In this case, a rapid change in torque due to a change in injection timing can be avoided.

  According to the present invention, the exhaust emission of the internal combustion engine can be reduced as much as possible under the condition that the amount of unburned components exhausted from the cylinder increases, such as when cold.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine control system according to the present invention.

  An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. The cylinder 2 of the internal combustion engine 1 is connected to the intake passage 30 through the intake port 3 and is connected to the exhaust passage 40 through the exhaust port 4.

  A throttle valve 5 for controlling the amount of air flowing through the intake passage 30 is provided in the middle of the intake passage 30. An air flow meter 6 that measures the amount of air flowing through the intake passage 30 is provided in the intake passage 30 upstream of the throttle valve 5.

  On the other hand, an exhaust purification device 7 is disposed in the exhaust passage 40. The exhaust purification device 7 includes a three-way catalyst, an NOx storage reduction catalyst, and the like, and purifies exhaust when it is in a predetermined activation temperature range.

  The internal combustion engine 1 is also provided with an intake valve 8 that opens and closes an open end of the intake port 3 facing the cylinder 2 and an exhaust valve 9 that opens and closes an open end of the exhaust port 4 facing the cylinder 2. The intake valve 8 and the exhaust valve 9 are opened and closed by an intake camshaft 10 and an exhaust camshaft 11, respectively.

  A spark plug 12 that generates a spark in the cylinder 2 and a fuel injection valve 13 that directly injects fuel into the cylinder 2 are attached to the upper part of the cylinder 2. A piston 14 is slidably inserted into the cylinder 2. The piston 14 is connected to the crankshaft 16 via a connecting rod 15.

  A crank position sensor 17 that detects a rotation angle of the crankshaft 16 is disposed in the vicinity of the crankshaft 16. Furthermore, a water temperature sensor 18 for measuring the temperature of the cooling water circulating through the internal combustion engine 1 is attached to the internal combustion engine 1.

  A variable valve mechanism 100 that changes the rotational phase of the intake camshaft 10 relative to the crankshaft 16 is attached to the intake camshaft 10.

  The internal combustion engine 1 configured as described above is provided with an ECU 19. The ECU 19 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like. The ECU 19 is electrically connected to various sensors such as the fuel pressure sensor 20 in addition to the air flow meter 6, the crank position sensor 17, and the water temperature sensor 18 described above. The fuel pressure sensor 20 is a sensor that measures fuel pressure in a delivery pipe (not shown).

  The ECU 19 electrically controls the fuel injection valve 13, the throttle valve 5, the spark plug 12, and the variable valve mechanism 100 based on the measurement values of the various sensors described above.

  For example, the ECU 13 switches between a plurality of combustion modes including homogeneous combustion and stratified combustion according to the operating conditions of the internal combustion engine 1.

  When the internal combustion engine 1 is in a homogeneous combustion operation, the ECU 19 operates the fuel injection valve 13 at a timing synchronized with the intake stroke of each cylinder 2, so that fuel and intake air are uniformly mixed in the entire area of the cylinder 2. Gas is formed.

  When the internal combustion engine 1 is stratified combustion operation, the ECU 19 uses the variable valve mechanism 100 to retard the valve opening timing (IVO) of the intake valve 8 to turn in each cylinder 2 (tumble flow). Or a swirl flow) is generated (corresponding to the generating means according to the present invention), and the fuel injection valve 13 is operated at a timing synchronized with the compression stroke of each cylinder 2 to form a combustible mixture layer in the vicinity of the spark plug 12 To do.

  Further, the ECU 19 performs attached fuel reduction control for reducing the fuel adhering to the wall surface in the cylinder 2 when the internal combustion engine 1 is in a cold state.

  When the internal combustion engine 1 is in a cold state, the in-cylinder temperature is low. When the in-cylinder temperature is low, the fuel (injected fuel) injected from the fuel injection valve 13 tends to adhere to the inner wall surface of the cylinder 2 and the piston 14. Most of the fuel (in-cylinder attached fuel) adhering to the inner wall surface of the cylinder 2 and the piston 14 is discharged from the cylinder without being burned without being used for combustion. At that time, if the exhaust gas purification device 7 has not been heated to the activation temperature range, the unburned components (HC, smoke, PM, etc.) described above are released into the atmosphere without being purified.

  In particular, when the internal combustion engine 1 is started at a low temperature, etc., the period from the start of the internal combustion engine 1 to the activation of the exhaust gas purification device 7 becomes longer and the amount of fuel adhering to the cylinder increases, so it is discharged into the atmosphere. The amount of unburned components may be excessive.

  On the other hand, in the attached fuel reduction control, the ECU 19 advances the operation timing (ignition timing) of the spark plug 12 before MBT when the in-cylinder attached fuel amount increases, thereby reducing the in-cylinder attached fuel amount. Accordingly, the amount of unburned components discharged from the cylinder 2 is also reduced.

  According to the earnest experiment and verification by the inventors of the present application, when the ignition timing is advanced before MBT, as shown in FIG. It has been found that the amount of unburned components is reduced.

  Although this mechanism has not been clearly clarified, it is thought to be due to the following mechanism.

  FIG. 3 shows the case where the ignition timing is advanced before MBT (ST1 in FIG. 3), the case where the ignition timing is set to MBT (ST2 in FIG. 3), and the ignition timing is compression top dead center. It is a figure which shows the result of having measured the state in the cylinder 2 in each when it is set to (TDC) (ST3 in FIG. 3). The solid line in FIG. 3 indicates the case where the ignition timing is over-advanced, the broken line indicates the case where the ignition timing is set to MBT, and the dashed line indicates the case where the ignition timing is set to compression top dead center (TDC). Yes.

  In FIG. 3, when the ignition timing is over-advanced, combustion occurs before the compression top dead center, compared to when the ignition timing is set to MBT and when the ignition timing is set to compression top dead center (TDC). The amount of air-fuel mixture produced increases. For this reason, the peak of the heat energy generated by the combustion of the air-fuel mixture (see the heat generation rate, generated heat amount, and combustion mass ratio in FIG. 3) shifts to before the compression top dead center.

Therefore, a cylinder in the period from the compression stroke to the expansion stroke is obtained by a synergistic effect of the temperature increase / pressure increase effect due to the combustion of the air-fuel mixture and the compression effect due to the upward movement of the piston 14 (operation from the bottom dead center to the top dead center). The peak values of internal pressure and in-cylinder temperature are significantly increased. As a result, it is considered that vaporization and oxidation of the fuel adhering to the cylinder 2 and / or the fuel before adhering to the cylinder 2 are promoted.

  Therefore, the ECU 19 causes the ignition timing to be over-advanced when the amount of in-cylinder attached fuel is expected to increase (in other words, when the condition for increasing the amount of in-cylinder attached fuel is satisfied). As a case where the amount of in-cylinder attached fuel is expected to increase, when the internal combustion engine 1 is cold-started, or when the internal combustion engine 1 is in a warm-up operation state, the actually measured value of the in-cylinder attached fuel amount exceeds the allowable amount. A case where the estimated value of the in-cylinder attached fuel amount exceeds the allowable amount or the like can be exemplified.

  As a method for actually measuring the amount of fuel adhering to the cylinder, a method for optically measuring the liquid film thickness in the cylinder 2 and a method for actually measuring it, or a sensor for measuring the conductivity in the cylinder 2 can be used. A method for converting the measured value of the sensor into the in-cylinder attached fuel amount can be exemplified.

  The method for estimating the amount of fuel adhering to the cylinder includes at least the cooling water temperature, the cumulative fuel injection amount from the time of engine startup, the cumulative intake air amount from the time of engine startup, the current fuel injection amount, the intake pressure, and the air-fuel ratio. A method of estimating from the correlation between one and the amount of in-cylinder attached fuel can be exemplified.

  In the case where the amount of in-cylinder attached fuel is expected to increase as described above, if the ignition timing is excessively advanced, the in-cylinder attached fuel can be reduced and the unburned component discharged from the cylinder 2 can be reduced. It can also be reduced.

  By the way, since the unburned component discharged from the cylinder 2 decreases as the ignition timing advance amount increases, it is preferable to increase the ignition timing advance amount as the in-cylinder attached fuel amount increases.

  However, if the advance amount of the ignition timing is increased when the internal combustion engine 1 is in a homogeneous combustion operation, the spark plug 12 may operate before the fuel and intake air in the cylinder 2 are mixed uniformly. If the spark plug 12 is operated before the fuel and air are uniformly mixed, poor ignition and misfire are likely to occur.

  FIG. 4 is a diagram showing the results of measuring the relationship between the in-cylinder temperature peak value and the injection timing. In FIG. 4, a broken line (MBT) indicates a measurement result when the ignition timing is set to MBT, and a one-dot broken line (over-advance angle A) indicates a measurement result when the ignition timing is over-advanced before MBT. The solid line (over-advance angle B) indicates the measurement result when the ignition timing is further advanced from the above-described over-advance angle A.

  The peak of the in-cylinder temperature when the ignition timing is set to MBT is highest when the injection timing is set during the intake stroke. On the other hand, the peak of the in-cylinder temperature when the ignition timing is over-advanced before MBT is highest when the injection timing is set during the compression stroke.

  Therefore, a method of setting the injection timing during the compression stroke when the ignition timing is excessively advanced (that is, a method of causing the internal combustion engine 1 to perform stratified combustion operation) can be considered. However, when the ignition timing over-advanced angle and the stratified charge combustion operation of the internal combustion engine 1 are simply combined, the timing at which the combustible mixture reaches the vicinity of the spark plug 12 (in other words, a combustible mixture layer forms near the spark plug 12). May be out of synchronization with the ignition timing.

Therefore, in the attached fuel reduction control in the present embodiment, the ECU 19 causes the internal combustion engine 1 to perform stratified combustion when the ignition timing is over-advanced, and a combustible air-fuel mixture layer near the over-advanced ignition timing and the ignition plug 12. The injection timing is adjusted so as to be synchronized with the timing at which the is formed. Hereinafter, the injection timing at which the ignition timing at which the advance angle is advanced and the timing at which the combustible air-fuel mixture layer is formed in the vicinity of the ignition plug 12 will be referred to as “adapted injection timing”.

  The suitable injection timing can be obtained based on the required time ΔT until the fuel injected from the fuel injection valve 13 reaches the vicinity of the spark plug 12 and the over-advanced ignition timing. That is, the timing obtained by subtracting the required time ΔT from the ignition timing that has been over-advanced can be regarded as the appropriate injection timing.

  The required time ΔT described above depends on the strength of the swirling flow (the number of times the swirling flow swirls per crankshaft rotation) and the fuel injection pressure. For example, the stronger the swirl flow, the faster the swirl speed. Therefore, the stronger the swirl flow, the shorter the required time ΔT. Further, the higher the fuel injection pressure, the faster the moving speed of the injected fuel. Thus, the higher the fuel injection pressure, the shorter the required time ΔT.

  The ECU 19 may appropriately calculate the required time ΔT based on the strength of the swirling flow and the fuel injection pressure, but the relationship between the required time ΔT and the strength of the swirling flow and the fuel injection pressure is experimentally determined in advance. It is also possible to obtain a map of the relationship between them.

  When the attached fuel reduction control is performed by such a procedure, the timing at which the combustible mixture reaches the vicinity of the spark plug 12 and the ignition timing can be synchronized. Therefore, when the internal combustion engine 1 is cold, the peak of the in-cylinder temperature can be increased as much as possible while preventing poor ignition of fuel and misfire. As a result, it is possible to suitably reduce unburned components discharged from the internal combustion engine 1.

  Hereinafter, the execution procedure of the adhered fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing an attached fuel reduction control routine in the present embodiment. This attached fuel reduction control routine is a routine stored in advance in the ROM or the like of the ECU 19 and is periodically executed by the ECU 19.

  In the attached fuel reduction control routine, the ECU 19 first determines in S101 whether or not the ignition timing over-advancement execution condition is satisfied. In other words, the ECU 19 determines whether or not a condition that the amount of in-cylinder attached fuel is expected to increase is satisfied.

  If a negative determination is made in S101, the ECU 19 once ends the execution of this routine. On the other hand, if an affirmative determination is made in S101, the ECU 19 proceeds to S102.

  In S102, the ECU 19 obtains the strength of the swirling flow (the number of times the swirling flow swirls per crankshaft rotation). The strength of the swirl flow can be calculated using the engine speed Ne, the intake air amount (measured value Ga of the air flow meter 6), and the opening / closing timing of the intake valve 8 as parameters.

  In S103, the ECU 19 reads the fuel injection pressure (the measured value Fp of the fuel pressure sensor 20).

  In S104, the ECU 19 determines the ignition timing at the excessive advance angle. As this determination method, it may be determined based on the in-cylinder attached fuel amount, or may be determined so that the combustion end timing of the air-fuel mixture is in the vicinity of the compression top dead center.

  In S105, the ECU 19 specifies the suitable injection timing based on the strength of the swirling flow and the fuel injection pressure obtained in S102 and S103. Specifically, as described above, the ECU 19 obtains the required time ΔT using the strength of the swirling flow and the fuel injection pressure as parameters. Next, the ECU 19 obtains the suitable injection timing by subtracting the required time ΔT from the over-advanced ignition timing.

  Thus, when the ECU 19 executes the attached fuel reduction control routine of FIG. 5, the over-advance angle means and the setting means according to the present invention are realized. As a result, in the internal combustion engine 1 provided with the fuel injection valve 13 capable of direct fuel injection into the cylinder 2, it is possible to reduce unburned components discharged from the cylinder while preventing poor fuel ignition and misfire. it can.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, the example in which the suitable injection timing is determined based on the strength of the swirling flow and the fuel injection pressure has been described. By the way, when the swirl flow is weak or the fuel injection pressure is low, the required time ΔT may become excessively long. In such a case, the suitable injection timing is set at an early stage, but there is a possibility that the convergence property of the swirling flow is lowered before the injected fuel reaches the vicinity of the spark plug 12.

  If the convergence of the swirl flow decreases before the injected fuel reaches the vicinity of the spark plug 12, the injected fuel may be diffused and dispersed in a wide range in the cylinder 2 before reaching the vicinity of the spark plug 12. There is. As a result, the fuel concentration in the vicinity of the spark plug 12 becomes too thin, and there is a possibility that the ignitability and the combustion stability will be reduced.

  Therefore, in the adhered fuel reduction control of this embodiment, the ECU 19 determines that the suitable injection timing determined based on the strength of the swirling flow and the fuel injection pressure is earlier than the predetermined timing (in other words, the required time ΔT is predetermined). When longer than the time), the swirl flow was strengthened.

  Here, the predetermined timing described above is determined based on the earliest injection timing among the injection timings (injection timings at which stratified combustion can be established) in which the converging property of the swirling flow is maintained. Further, the predetermined time is determined based on the longest required time among the required times during which the swirl flow can be converged (the required time during which stratified combustion can be established).

  When the swirl flow is strengthened, the convergence property of the swirl flow is enhanced. For this reason, the injected fuel is not dispersed or diffused before reaching the vicinity of the spark plug 12. As a result, a combustible mixture layer can be formed in the vicinity of the spark plug 12.

  As a method for enhancing the swirl flow, a method of retarding the valve opening timing of the intake valve 8 and / or reducing the lift amount of the intake valve 8 using the variable valve mechanism 100 can be exemplified. When the opening timing of the intake valve 8 is retarded and / or the lift amount of the intake valve 8 is decreased, the inflow speed when the intake air flows into the cylinder 2 is increased. In this case, the swirling speed of the swirling flow is increased. As a result, the number of times the swirling flow turns per crankshaft rotation increases.

When the swirl flow is strengthened, the timing at which the injected fuel reaches the vicinity of the spark plug 12 is advanced. Therefore, it is desirable for the ECU 19 to re-determine the appropriate injection timing based on the strength of the swirling flow after strengthening.

  Hereinafter, the execution procedure of the adhered fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing an attached fuel reduction control routine in the present embodiment. In FIG. 6, the same reference numerals are assigned to the same processes as those in the attached fuel reduction control routine (see FIG. 5) of the first embodiment described above.

  In the adhered fuel reduction control routine of FIG. 6, the ECU 19 proceeds to S201 after determining the suitable injection timing in S105. In S201, the ECU 19 determines whether or not the suitable injection timing determined in S105 is earlier than a predetermined timing.

  If a negative determination is made in S201, the ECU 19 once ends the execution of this routine. On the other hand, when a positive determination is made in S201, the ECU 19 proceeds to S202.

  In S202, the ECU 19 performs a process for enhancing the swirling flow. Specifically, as described above, the ECU 19 uses the variable valve mechanism 100 to retard the opening timing (IVO) of the intake valve 8 and / or reduces the lift amount of the intake valve 8. Process.

  At this time, the retard amount of the intake valve 8 and / or the decrease amount of the lift amount of the intake valve 8 may be a predetermined fixed amount, or as the difference between the suitable injection timing and the predetermined timing increases. May be a variable amount.

  When the ECU 19 finishes executing the process of S202, the ECU 19 returns to S102 to re-determine the appropriate injection timing.

  Thus, when the ECU 19 executes the attached fuel reduction control routine as shown in FIG. 6, the control means according to the present invention is realized. Therefore, even when the swirl flow is weak or the fuel injection pressure is low, the ignition timing can be over-advanced while suppressing a decrease in ignitability and a decrease in combustion stability.

<Example 3>
Next, a third embodiment of the present invention will be described with reference to FIG. Here, a configuration different from the second embodiment described above will be described, and the description of the same configuration will be omitted.

  In this embodiment, when the swirl flow is weak or the fuel injection pressure is low, the fuel injection pressure is increased instead of strengthening the swirl flow. When the fuel injection pressure is increased, the kinetic energy (movement speed) of the injected fuel increases. In this case, since the kinetic energy of the injected fuel is added to the kinetic energy of the swirling flow, the strength of the swirling flow is increased. Therefore, the same effect as when the swirl flow is enhanced can be obtained.

  Examples of a method for increasing the fuel injection pressure include a method for increasing the discharge pressure of a fuel pump (not shown), a method for increasing the valve opening pressure of a relief valve provided in a delivery pipe or a fuel supply pipe, and the like.

  Hereinafter, the execution procedure of the adhered fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing an attached fuel reduction control routine in the present embodiment. In FIG. 7, the same reference numerals are assigned to the same processes as those in the attached fuel reduction control routine (see FIG. 6) of the second embodiment described above.

  In the adhered fuel reduction control routine of FIG. 7, the ECU 19 proceeds to S301 if an affirmative determination is made in S201.

  In S301, the ECU 19 performs a process for increasing the fuel injection pressure. Specifically, as described above, the ECU 19 performs a process of increasing the discharge pressure of the fuel pump and / or a process of increasing the valve opening pressure of the relief valve provided in the delivery pipe or the fuel supply pipe.

  At this time, the amount of increase in the discharge pressure of the fuel pump and / or the valve opening pressure of the relief valve may be a predetermined fixed amount, or a variable that increases as the difference between the suitable injection timing and the predetermined timing increases. It may be an amount.

  After completing the processing of S301, the ECU 19 returns to S102 in order to re-determine the appropriate injection timing.

  Thus, when the ECU 19 executes the attached fuel reduction control routine as shown in FIG. 7, the same effects as those of the second embodiment described above can be obtained. The second embodiment described above and this embodiment can be combined as much as possible.

  For example, when the intake air amount is extremely small, there is a possibility that the swirl flow is not sufficiently strengthened even if the valve opening timing of the intake valve 8 is retarded and / or the lift amount of the intake valve 8 is reduced. In such a case, the convergence property of the swirl flow may be improved by increasing the fuel injection pressure.

  On the other hand, when the fuel injection amount is extremely small, there is a possibility that the convergence of the swirling flow cannot be sufficiently improved even if the fuel injection pressure is increased. In such a case, the convergence property of the swirling flow may be enhanced by strengthening the swirling flow.

  Further, when the intake air amount and the fuel injection amount are extremely small, there is a possibility that the convergence property of the swirling flow cannot be sufficiently improved only by either the strengthening of the swirling flow or the increase of the fuel injection pressure. In such a case, both the swirl flow enhancement and the fuel injection pressure increase may be performed.

<Example 4>
Next, a fourth embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  There is a possibility that the injection timing changes greatly at the start or during execution of the attached fuel reduction control. For example, when the execution of the attached fuel reduction control is started from a state in which the internal combustion engine 1 is in a homogeneous combustion operation, as shown in FIG. 8, prior injection timing synchronized with the intake stroke (A in FIG. 8). To a new injection timing synchronized with the compression stroke (B in FIG. 8). Thus, when the fuel injection timing is significantly changed, the generated torque of the internal combustion engine 1 changes abruptly.

On the other hand, in the attached fuel reduction control of the present embodiment, the ECU 19 performs a process for suppressing a sudden change in torque when the injection timing is changed (hereinafter referred to as “transition process”). As a specific execution method of the transition process, there is a method of gradually shifting the injection timing from the previous injection timing to the new injection timing, and the injection amount at the new injection timing while gradually decreasing the injection amount at the previous injection timing. And a method of increasing or decreasing the injection amount at the new injection timing so that the generated torque at the previous injection timing is equal to the generated torque at the new injection timing.

  When such a transition process is performed, it is possible to avoid a sudden change in the generated torque due to the execution of the attached fuel reduction control.

  Hereinafter, the execution procedure of the adhered fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing an attached fuel reduction control routine in the present embodiment. In FIG. 9, the same reference numerals are assigned to the same processes as those in the attached fuel reduction control routine (see FIG. 5) of the first embodiment described above.

  In the adhered fuel reduction control routine of FIG. 9, when the ECU 19 finishes determining the suitable injection timing in S105, the process proceeds to S401. In S401, the ECU 19 calculates a difference (torque step) Δtrq between the generated torque at the previous injection timing and the generated torque at the appropriate injection timing calculated in S105. At that time, the relationship between the engine operating conditions including the injection timing and the generated torque (for example, the correlation as shown in FIG. 8) may be mapped in advance.

  In S402, the ECU 19 determines whether or not the torque step Δtrq calculated in S401 is greater than a predetermined value α. The predetermined value α is a value corresponding to an allowable limit value of the magnitude of torque fluctuation.

  If a negative determination is made in S402 (Δtrq ≦ α), the ECU 19 once ends the execution of this routine. On the other hand, if a positive determination is made in S402 (Δtrq> α), the ECU 19 proceeds to S403.

  In S403, the ECU 19 executes the transition process as described above. The transition means according to the present invention is realized by the ECU 19 executing the process of S403.

  As described above, when the ECU 19 performs the attached fuel reduction control according to the attached fuel reduction control routine of FIG. 9, it is possible to avoid a sudden change in torque accompanying the execution of the attached fuel reduction control.

<Other embodiments>
In the first to fourth embodiments described above, the variable valve mechanism 100 has been exemplified as an embodiment of the generating means according to the present invention. However, even with the airflow control valve 31 as shown in FIG. Good.

  The airflow control valve 31 is a valve that is disposed in the intake port 3 downstream of the fuel injection valve 13 and is rotatable about a fulcrum provided on the bottom surface of the intake port 3. FIG. 10 shows a state in which the airflow control valve 31 is closed.

  When the airflow control valve 31 is closed as shown in FIG. 10, the airflow is biased upward in the intake port 3, and a tumble flow is generated in the cylinder 2. At that time, the strength (tumble ratio) of the tumble flow becomes stronger as the opening degree of the air flow control valve 31 becomes smaller.

  Therefore, the ECU 19 does not attempt to retard the opening timing (IVO) of the intake valve 8 or reduce the lift amount of the intake valve 8 when the internal combustion engine 1 is subjected to stratified combustion or to strengthen the swirl flow. You may make it reduce the opening degree of the airflow control valve 31. FIG.

Note that the airflow control valve may be disposed at the straight port in an internal combustion engine having a swirl port and a straight port per cylinder. In this case, when the opening degree of the airflow control valve is reduced, the amount of intake air flowing through the straight port decreases and the amount of intake air flowing through the swirl port increases, so that a swirl flow is generated in the cylinder. The strength (swirl ratio) of the swirl flow at that time increases as the opening of the airflow control valve decreases.

  Therefore, the ECU 19 does not attempt to retard the opening timing (IVO) of the intake valve 8 or reduce the lift amount of the intake valve 8 when the internal combustion engine 1 is subjected to stratified combustion or to strengthen the swirl flow. You may make it reduce the opening degree of an airflow control valve.

It is a figure which shows schematic structure of the control system of an internal combustion engine. It is a figure which shows the relationship between ignition timing and the discharge | emission amount of an unburned component. It is a figure which shows the relationship between an ignition timing and the state in a cylinder. It is a figure which shows the relationship between the peak of in-cylinder temperature, and fuel injection timing. It is a flowchart which shows the adhesion fuel reduction control routine in a 1st Example. It is a flowchart which shows the adhesion fuel reduction control routine in a 2nd Example. It is a flowchart which shows the adhesion fuel reduction control routine in a 3rd Example. It is a figure which shows the relationship between the generated torque of an internal combustion engine, and the injection timing. It is a flowchart which shows the adhesion fuel reduction control routine in a 4th Example. It is a figure which shows the other structural example of the control system of an internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Intake port 4 ... Exhaust port 5 ... Throttle valve 6 ... Air flow meter 8 .... ... Intake valve 9 ... Exhaust valve 10 ... Intake side camshaft 11 ... Exhaust side camshaft 12 ... Ignition plug 13 ... Fuel injection valve 17 ...・ Crank position sensor 18 ・ ・ ・ ・ Water temperature sensor 19 ・ ・ ・ ・ ECU
20 ... Fuel pressure sensor 30 ... Intake passage 40 ... Exhaust passage 31 ... Airflow control valve 100 ... Variable valve mechanism

Claims (5)

A fuel injection valve for injecting fuel into a cylinder of the internal combustion engine;
A spark plug for causing a spark in the cylinder;
Over-advance means for over-advancing the ignition timing of the spark plug before MBT;
Generating means for generating a swirling flow in the cylinder;
When the ignition timing is over-advanced before MBT by the over-advance means, the injection timing of the fuel injection valve is set during the compression stroke so that the combustion mode of the internal combustion engine is stratified combustion. Setting means for setting an injection timing of the fuel injection valve based on a moving speed of the fuel injected from the fuel injection valve and a state of a swirling flow generated in the cylinder;
Control means for strengthening the swirl flow by the generating means when the injection timing set by the setting means is earlier than a predetermined timing;
Control system for an internal combustion engine, wherein the obtaining Bei a. A fuel injection valve for injecting fuel into a cylinder of the internal combustion engine;
A spark plug for causing a spark in the cylinder;
Over-advance means for over-advancing the ignition timing of the spark plug before MBT;
Generating means for generating a swirling flow in the cylinder;
When the ignition timing is over-advanced before MBT by the over-advance means, the injection timing of the fuel injection valve is set during the compression stroke so that the combustion mode of the internal combustion engine is stratified combustion. Setting means for setting an injection timing of the fuel injection valve based on a moving speed of the fuel injected from the fuel injection valve and a state of a swirling flow generated in the cylinder;
If the injection timing set by the pre-Symbol setting means is earlier than a predetermined timing, a control means for increasing the moving speed of the fuel injected from the fuel injection valve,
Control system for an internal combustion engine, wherein the obtaining Bei a. Oite to claim 1 or 2, when changing the actual injection timing in accordance with the injection timing set by the setting unit further migration means for shifting gradually injection timing from the pre-injection timing to the new injection timing An internal combustion engine control system comprising: A fuel injection valve for injecting fuel into a cylinder of the internal combustion engine;
A spark plug for causing a spark in the cylinder;
Over-advance means for over-advancing the ignition timing of the spark plug before MBT;
Setting means for setting the injection timing of the fuel injection valve during the compression stroke so that the combustion mode of the internal combustion engine is stratified combustion when the ignition timing is over-advanced before MBT by the over-advance angle means When,
When changing the actual injection timing in accordance with the injection timing set by the pre-Symbol setting means, and gradual transition hand stage to increase the injection quantity in the new injection timing with gradually decreasing the injection amount in pre-injection timing ,
Control system for an internal combustion engine, wherein the obtaining Bei a. 4. When the actual injection timing is changed according to the injection timing set by the setting means according to claim 1, the injection amount at the previous injection timing is gradually decreased and the new injection timing is changed. A control system for an internal combustion engine, further comprising transition means for gradually increasing an injection amount.

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