JP4501743B2 - In-cylinder direct injection spark ignition internal combustion engine controller - Google Patents

Description

  The present invention relates to an in-cylinder direct injection spark ignition internal combustion engine that directly injects fuel into a cylinder, and more particularly to control of the injection timing and ignition timing.

Patent Document 1 discloses that when an exhaust purification catalytic converter is in an unwarmed state lower than an activation temperature, fuel is injected during the compression stroke, and the ignition timing is retarded from the compression top dead center. Technology is disclosed.
JP 2001-336467 A

  In order to raise the exhaust gas temperature and reduce HC in order to achieve early activation of the catalyst when the internal combustion engine is cold, it is desirable to retard the ignition timing as much as possible, but if the ignition timing is significantly retarded Since the combustion stability deteriorates, it cannot be retarded from a certain limit determined from the viewpoint of combustion stability. In the conventional technique such as Patent Document 1, it is difficult to ensure stable combustion, particularly under conditions such as cold, and the retard limit of the ignition timing determined from the combustion stability is relatively advanced, which is sufficient. The ignition timing delay cannot be realized.

  The present invention provides a control device for an in-cylinder direct injection spark ignition internal combustion engine that includes a fuel injection valve that directly injects fuel into a cylinder and that includes an ignition plug. When it is necessary to raise the exhaust gas temperature, such as when the engine is cold, the fuel injection is performed as the top dead center injection operation mode. The injection start timing is before the compression top dead center and the injection end timing is after the compression top dead center. In this manner, the ignition is performed in a period straddling the compression top dead center, and ignition is performed after the compression top dead center delayed from the injection start timing. In particular, at the time of a transient in which the load increases at a speed equal to or higher than a predetermined change speed during the top dead center injection operation mode, at least a part of the fuel is injected during the intake stroke.

  FIG. 1 illustrates a fuel injection period and an ignition timing in the top dead center injection operation mode of the present invention together with a change in in-cylinder pressure. As shown in FIG. 1A, the injection start timing ITS is a compression top dead center. Before (TDC), the injection end timing ITE is after the compression top dead center (TDC). The length of the injection period T during that time corresponds to the injection amount. The ignition timing ADV is after compression top dead center (TDC), and is a timing delayed by a predetermined crank angle (for example, 10 ° CA to 25 ° CA) from the injection start timing ITS. This delay period D generally correlates with the distance from the fuel injection valve to the spark plug.

  The injection start timing ITS and the injection end timing ITE are controlled so that the period before the compression top dead center in the first half and the period after the compression top dead center in the second half are substantially equal with the compression top dead center (TDC) as the center. You may make it do.

  FIG. 2 shows the piston position change amount and the combustion chamber volume change amount due to the piston stroke in one cycle of the internal combustion engine. As shown in the figure, the amount of change per unit crank angle is the largest near the middle position of the stroke, and is very small near the bottom dead center (BDC) and near the top dead center (TDC). Therefore, in the vicinity of the compression top dead center where the fuel injection is performed in the present invention, the piston position change and volume change are very small, and a stable field that is not affected by the piston movement or the like can be formed.

  In the cylinder, a relatively large gas flow such as a swirl flow or a tumble flow is generated in the intake stroke and remains in the compression stroke. However, a large flow such as a swirl flow or a tumble flow is When the piston reaches near the compression top dead center and the combustion chamber becomes narrow, it collapses rapidly. FIG. 3 shows a change in flow velocity of a large flow in the combustion chamber under various engine speeds. As shown in the figure, a swirl flow or a tumble flow having a strength corresponding to the rotation speed is generated. Collapses rapidly before reaching compression top dead center (360 ° CA). Therefore, in the present invention, the fuel spray injected near the compression top dead center is not moved by a large flow such as a swirl flow or a tumble flow, and always forms a spray in a stable manner on the spark plug. Is possible.

  On the other hand, the energy of a relatively large flow such as the swirl flow or the tumble flow described above transitions to minute turbulence as the flow collapses. Therefore, the minute disturbance in the combustion chamber increases rapidly just before the compression top dead center. FIG. 4 shows the intensity of the minute turbulence caused by the collapse of the flow shown in FIG. 3 as a so-called turbulent flow rate converted to a flow velocity, and as shown in the figure, immediately before the compression top dead center. , Disturbances increase greatly. Such minute disturbances contribute to the activation of the combustion field, and a combustion improving action is obtained.

  In other words, the field in the combustion chamber near the compression top dead center where the fuel is injected does not have a large flow that moves the spray, and there are many minute disturbances that activate the combustion, It is a very stable place against the movement of the piston. Therefore, stable combustion is possible with the ignition timing retarded from the compression top dead center, and the retard limit of the ignition timing that is limited in terms of combustion stability is on the retard side. For this reason, the exhaust gas temperature can be raised significantly by a large retardation of the ignition timing, and the HC emission amount is reduced.

  Here, in the top dead center injection operation mode as described above, when the load suddenly increases due to a sudden increase in the accelerator opening or the input of an auxiliary machine load, the fuel injection around the compression top dead center as described above is performed. Even if the injection amount is increased, the torque rise is relatively slow, which is not preferable in terms of torque response. Further, when the fuel injection amount exceeds a certain level, an excessively rich mixture of air-fuel mixture is generated, which causes the deterioration of smoke.

Therefore, in the present invention, during a transition in which the load increases at a speed equal to or higher than a predetermined change speed during the top dead center injection operation mode , at least a part of the fuel is injected during the intake stroke only for a predetermined period . That is, as shown in FIG. 1B, a part of the fuel is injected as the early injection I2 during the intake stroke prior to the main injection I1 in the period over the compression top dead center. Alternatively, the entire amount of fuel is injected during the intake stroke.

  Thus, the energy of the fuel injected during the intake stroke as the early injection I2 is converted into torque with higher efficiency than the main injection. Accordingly, the torque response during the transition is improved. Then, the fuel injected by the early injection I2 diffuses into the cylinder before the injection timing of the main injection I1, and the fuel by the main injection I1 is injected here, so that an excessive air-fuel mixture lump and smoke is generated. Is suppressed.

  In the present invention, it is desirable to increase the intake stroke injection, that is, the injection amount of the early injection I2, as the load increasing rate is larger. In this case, it is desirable that the injection amount of the intake stroke injection be equal to or longer than a predetermined minimum injection time of the fuel injection valve.

  As the load increases, the total fuel injection amount corresponding to the load itself increases, but the injection amount of the main injection I1 increases as the total fuel injection amount increases while the early injection I2 is additionally performed. Or may be kept constant without being changed, or may be decreased in consideration of the injection amount of the early injection I2.

  The intake stroke injection, that is, the early injection I2 according to the present invention may be performed at the beginning of the transition, and thereafter, it is desirable to gradually decrease the injection amount of the early injection I2 with time. Note that the injection amount of the main injection I1 is gradually increased as the injection amount of the early injection I2 decreases.

  Further, at the time of transition, the ignition timing can be corrected together with the intake stroke injection. Thereby, it is possible to finely adjust the torque of the internal combustion engine with good responsiveness.

  According to the present invention, stable combustion can be obtained in a state where the ignition timing is significantly retarded from the compression top dead center. For example, when the internal combustion engine is cold, the exhaust gas temperature is raised and the catalyst is accelerated. Activation can be achieved and HC emissions can be reduced. When the load increases rapidly, at least a part of the fuel is injected during the intake stroke, so that the torque response can be improved and the deterioration of smoke can be avoided.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  5 to 7 show an embodiment of a direct injection type spark ignition internal combustion engine to which the present invention is applied. In particular, FIGS. 5 and 6 show the configuration of one cylinder. Indicates the system configuration of the entire organization.

  As shown in FIGS. 5 and 6, a piston 3 is slidably disposed in a cylinder 2 formed in the cylinder block 1, and a cylinder head 4 fixed to the upper surface of the cylinder block 1 and the piston 3 A combustion chamber 5 is formed between them. The cylinder head 4 is formed with an intake port 7 that is opened and closed by an intake valve 6 and an exhaust port 9 that is opened and closed by an exhaust valve 8. A pair of intake valves 6 and a pair of exhaust valves 8 are provided for one cylinder, and an ignition plug 10 is disposed at the center of the ceiling surface of the combustion chamber 5 surrounded by these four valves. . Further, in this embodiment, the intake port 7 is provided with a partition wall 11 that divides the intake port 7 into two upper and lower flow paths so that the tumble flow can be strengthened depending on the operating state. A tumble control valve 12 that opens and closes the lower flow path at the upstream end is provided. As can be easily understood by those skilled in the art, the tumble flow is strengthened when the lower flow path is closed by the tumble control valve 12, and the tumble flow is weakened when the tumble control valve 12 is opened. The tumble control valve 12 is not necessarily essential in the present invention, and can be omitted. Alternatively, a known swirl control valve may be provided.

  A fuel injection valve 15 for directly injecting fuel into the cylinder is disposed below the intake port 7 of the cylinder head 4, more specifically at a position between the pair of intake ports 7. The fuel injection valve 15 is arranged so as to inject fuel along a direction orthogonal to a piston pin (not shown) in the plan view, and is arranged so as to be directed obliquely downward in the sectional view of FIG. However, the downward inclination angle is relatively small, that is, the fuel is injected in a direction close to the horizontal.

  On the other hand, the top of the piston 3 has a convex shape along the inclination of the ceiling surface of the combustion chamber 5 that forms a pent roof type, and a concave portion 16 having a substantially rectangular shape in plan view is formed at the center. Yes. The bottom surface of the recess 16 forms an arc surface having a predetermined radius of curvature or a curved surface approximating an arc so as to follow the tumble flow.

  As shown in FIG. 7, the internal combustion engine of this embodiment is, for example, an in-line four-cylinder engine, and a catalytic converter 22 for purifying exhaust gas is provided in an exhaust passage 21 to which an exhaust port 9 of each cylinder is connected. An air-fuel ratio sensor 23 such as an oxygen sensor is disposed on the upstream side. The intake passage 24 to which the intake port 7 of each cylinder is connected is provided with an electronically controlled throttle valve 25 that is opened and closed by a control signal on the inlet side. An exhaust gas recirculation passage 26 is provided between the exhaust passage 21 and the intake air passage 24, and an exhaust gas recirculation control valve 27 is interposed in the middle. Further, the tumble control valves 12 of the respective cylinders are configured to be simultaneously opened and closed by a negative pressure type tumble control actuator 29 that is operated by a suction negative pressure introduced via a solenoid valve 28.

  The fuel injection valve 15 is supplied with the fuel adjusted to an appropriate pressure by the fuel pump 31 and the pressure regulator 32 via the fuel gallery 33. Therefore, when the fuel injection valve 15 of each cylinder is opened by the control pulse, an amount of fuel corresponding to the valve opening period is injected. The ignition plug 10 of each cylinder is connected to an ignition coil 34.

  The fuel injection timing, injection amount, ignition timing, etc. of the internal combustion engine are controlled by the control unit 35. The control unit 35 includes a detection signal of an accelerator opening sensor 30 that detects the amount of depression of an accelerator pedal, a detection signal of a crank angle sensor 36, a detection signal of an air-fuel ratio sensor 23, and a detection of a water temperature sensor 37 that detects a cooling water temperature. Signals, etc. are input.

  In the internal combustion engine configured as described above, when the warm-up is completed, for example, when the cooling water temperature exceeds 80 ° C., normal stratified combustion operation and homogeneous combustion operation are performed.

  That is, in a predetermined region on the low speed and low load side, as a normal stratified combustion operation mode, fuel injection is performed at an appropriate time in the compression stroke, with the tumble control valve 12 basically closed. Ignition is performed before the top dead center. In this operation mode, fuel injection always ends before compression top dead center. The fuel injected toward the piston 3 during the compression stroke is collected in the vicinity of the spark plug 10 using a tumble flow swirling along the recess 16 and ignited there. Therefore, stratified combustion with an average air-fuel ratio lean is realized.

  Further, in a predetermined region on the high speed and high load side after the warm-up is completed, fuel injection is performed during the intake stroke under the condition that the tumble control valve 12 is basically opened as a normal homogeneous combustion operation mode. And ignition is performed at the MBT point before the compression top dead center. In this case, the fuel becomes a homogeneous air-fuel mixture in the cylinder and is basically operated near the stoichiometric air-fuel ratio.

  On the other hand, when the cooling water temperature of the internal combustion engine is 80 ° C. or lower, that is, when the warm-up is not completed, the top dead center is used to activate the catalytic converter 22, that is, promote the temperature rise and reduce the HC emission amount. It becomes the injection operation mode. In the top dead center injection operation mode, as shown in FIG. 1A, the injection start timing ITS is before the compression top dead center (TDC), and the injection end timing ITE is after the compression top dead center (TDC). Thus, fuel injection is performed across the compression top dead center. The ignition timing ADV is after compression top dead center (TDC), and is ignited at a timing delayed by 10 ° CA to 25 ° CA from the injection start timing ITS. During this delay period, the fuel spray just reaches the vicinity of the spark plug 10 and forms a combustible air-fuel mixture in the vicinity of the spark plug 10, so that ignition combustion is surely performed and stratified combustion is performed. At this time, the fuel injection amount is controlled so that the average air-fuel ratio becomes the stoichiometric air-fuel ratio.

  In this embodiment, the fuel injection timing is controlled so that the injection start timing ITS becomes a predetermined crank angle, and the injection end timing ITE is determined by the injection start timing ITS and the fuel injection amount (injection time). . The injection start timing ITS and the injection end timing ITE are obtained based on the fuel injection amount so that the period before the compression top dead center and the period after the compression top dead center in the fuel injection period are equal. Is also possible.

  As described above, the field in the combustion chamber near the compression top dead center where fuel is injected in this top dead center injection operation mode does not have a large flow that causes the spray to move due to the collapse of the large flow, Along with the collapse of the large flow, there are many minute disturbances that activate the combustion, and the field becomes very stable against the movement of the piston. Then, by performing fuel injection at a high pressure in a stable field where there is no such a large flow, minute turbulence can be positively generated in the cylinder by the energy of the spray itself. Therefore, stable combustion is possible with the ignition timing retarded from the compression top dead center, and the retard limit of the ignition timing that is limited in terms of combustion stability is on the retard side. For this reason, the exhaust gas temperature can be raised significantly by a large retardation of the ignition timing, and the HC emission amount is reduced.

  Here, when the load suddenly increases, more specifically, at the time of a transient in which the load increases at a speed equal to or higher than a predetermined change speed, as shown in FIG. 1B, the main injection I1 in the period across the compression top dead center Prior to this, during the intake stroke, part of the fuel is injected as early injection I2. The injection amount of the early injection I2 varies depending on the load increasing speed. As shown in FIG. 8, the larger the load increasing speed, for example, the change rate ΔTVO of the throttle valve opening TVO, the greater the injection amount of the early injection I2. It is done. In the region where the change rate ΔTVO is small, the fuel injection valve 15 is limited to a predetermined minimum injection time determined in terms of responsiveness, control accuracy, and the like, and the injection amount of the early injection I2 does not decrease any further.

  Further, the injection amount of the main injection I1 when performing the early injection I2 is obtained by subtracting the injection amount of the early injection I2 from the total fuel injection amount commensurate with the required torque.

  As one of the sudden increases in load, when dealing with an auxiliary load applied on and off, the injection amount of the early injection I2 may be given as a constant value determined for each auxiliary device. That is, when a certain auxiliary machine is turned on, a predetermined amount of early injection I2 is performed for a short time immediately after the switching.

  Further, the final torque of the internal combustion engine can be finely adjusted with good responsiveness by correcting the ignition timing.

  Although FIG. 9 shows the operation mode during cold operation, as shown in FIG. 9, the top dead center injection operation mode is canceled in the high load region and the high speed region even during cold operation. As the normal mode, normal stratified combustion operation or homogeneous combustion operation is performed.

  FIG. 10 is a flowchart showing an outline of the control of this embodiment. First, in step 1, it is determined whether or not a prohibition condition for the top dead center injection operation mode is satisfied. For example, when the cooling water temperature exceeds 80 ° C., or in the high load region or high speed region shown in FIG. 9, the top dead center injection operation mode is prohibited. Operate or perform homogeneous combustion operation. If the top dead center injection operation mode is not prohibited, the process proceeds to step 3 to determine whether or not it is within a predetermined period after a sudden increase in load. If “NO” here, the process proceeds to a step 4 to perform the operation in the top dead center injection operation mode, in particular, only the main injection I1.

  On the other hand, if “YES” in the step 3, the process proceeds to a step 5, and the operation by the early injection I2 and the main injection I1 is performed. Specifically, at the first time, the injection amount of the early injection I2 is determined on the basis of the change rate ΔTVO of the throttle valve opening TVO, and the injection amount of the main injection I1 is considered in consideration of the injection amount of the early injection I2. To decide. Then, the early injection I2 is performed during the intake stroke, and the main injection I1 is performed during the period across the compression top dead center. From the second time onward, the injection amount of the early injection I2 is gradually decreased from the initial value, and the injection amount of the main injection I1 is gradually increased correspondingly, and each injection is similarly performed at a predetermined timing.

The characteristic view which showed an example of the fuel-injection period and ignition timing of this invention. The characteristic figure of the piston position change amount and volume change amount during a cycle. The characteristic figure which shows the change in the cycle of a big flow. The characteristic view which shows the change in the cycle of a minute disturbance. Sectional drawing which shows one Example of a direct injection type spark ignition internal combustion engine. FIG. FIG. 2 is a configuration explanatory view showing the system configuration of the entire internal combustion engine. The characteristic view which shows the relationship between the injection quantity of the early injection I2, and the change speed (DELTA) TVO of the throttle valve opening degree TVO. The characteristic view which shows the operation mode at the time of the cold machine with respect to engine operation conditions. The flowchart which shows the outline of control.

Explanation of symbols

3 ... Piston 5 ... Combustion chamber 10 ... Spark plug 15 ... Fuel injection valve

Claims (9)

In a control device for a direct injection type spark ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a cylinder and having an ignition plug, the top dead center injection operation mode is set in a predetermined operating state. , Fuel injection is performed in a period straddling the compression top dead center such that the injection start time is before the compression top dead center and the injection end time is after the compression top dead center, and the compression top dead is delayed from the injection start time. performs ignition after a point, during a transient the upper load in dead point injection operation mode is increased at a predetermined rate of change or a rate of only a predetermined period, so that injected during the intake stroke at least a portion of the fuel The in- cylinder direct injection is characterized in that, after the intake stroke injection is performed at the beginning of the transition, the injection amount of the intake stroke injection is gradually decreased as time elapses. Injected spark ignition Institutions of the control device.   2. The control apparatus for a direct injection type spark ignition internal combustion engine according to claim 1, wherein the amount of intake stroke injection is increased as the load increase rate is increased.   3. The control apparatus for a direct injection type spark ignition internal combustion engine according to claim 2, wherein the injection amount of the intake stroke injection is equal to or longer than a predetermined minimum injection time of the fuel injection valve. The control device for a direct injection type spark ignition internal combustion engine according to any one of claims 1 to 3 , wherein the ignition timing is corrected together with the intake stroke injection at the time of transition. The in-cylinder direct injection spark ignition internal combustion engine control device according to any one of claims 1 to 4 , wherein the intake stroke injection is performed at the time of input of an auxiliary machine load as a transition time. The in-cylinder direct injection type according to any one of claims 1 to 5 , wherein the top dead center injection operation mode is executed when a temperature increase of the exhaust gas temperature is required as a predetermined operation state. Control device for spark ignition internal combustion engine. The in-cylinder direct injection type according to any one of claims 1 to 6 , wherein the ignition timing is a timing delayed by 10 ° CA to 25 ° CA from an injection start timing of main injection straddling the compression top dead center. Control device for spark ignition internal combustion engine. The in-cylinder according to any one of claims 1 to 7 , wherein a period before the compression top dead center and a period after the compression top dead center in the fuel injection period of the main injection straddling the compression top dead center are substantially equal. Control device for a direct injection spark ignition internal combustion engine. The control device for a direct injection type spark ignition internal combustion engine according to any one of claims 1 to 8 , wherein the average air-fuel ratio is substantially the stoichiometric air-fuel ratio.

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