JP2006017062A - Control device for cylinder direct injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize temperature rise of exhaust gas temperature and reduction of HC emission quantity at a time of cold engine by compatibly achieving great ignition timing delay and stabilization of combustion. <P>SOLUTION: Normal stratified combustion operation and homogeneous combustion operation is performed under a warming up completion condition where cooling water temperature of the internal combustion engine exceeds 80°. Top dead center injection operation is performed to promote activation of a catalyst converter and reduction of HC emission amount under a cold engine condition where cooling water temperature is 80° or less. Injection start timing ITS is before compression top dead center TDC and Injection completion timing ITE is after compression top dead center TDC and fuel injection is performed over compression top dead center in top dead center injection operation. Ignition timing ADV is after compression top dead center and ignition is done at timing delayed from ignition start timing ITS by 15-20°CA. Since swirl flow and tumble flow collapse at compression top dead center and stable condition is formed, combustion stability is improved and great ignition timing delay can be done. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

In Patent Document 1, when the exhaust gas-purifying catalytic converter is in an unwarmed state lower than the activation temperature, the entire fuel injection amount is divided into two injections, an early injection and a late injection. A technique is disclosed in which early injection is performed during the intake stroke, late injection is performed during the compression stroke, and the ignition timing is retarded from the MBT point.
JP 2000-45843 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 above-described conventional technology, it is difficult to ensure stable combustion, particularly under conditions such as cold, the ignition timing delay limit determined from the combustion stability is relatively advanced, and the ignition timing is sufficiently retarded. 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 during operation, fuel injection is performed across the compression top dead center so that the injection start time is before the compression top dead center and the injection end time is after the compression top dead center. The ignition is performed during the period and after compression top dead center delayed from the injection start timing.

  For example, it is desirable that the ignition timing be delayed by 15 ° CA to 20 ° CA from the injection start timing.

  It is also possible to control 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 substantially equal.

  FIG. 1 exemplifies the fuel injection period and ignition timing of the present invention together with the in-cylinder pressure change. The injection start timing ITS is before compression top dead center (TDC), and the injection end timing ITE is compression top dead center (TDC). Later. 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, 15 ° CA to 20 ° 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.

  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 significantly increased by a large retardation of the ignition timing, and the HC emission amount is reduced.

  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.

  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, a partition wall 11 is provided in the intake port 7 so as to partition the intake port 7 into two upper and lower flow paths so that the tumble flow can be strengthened depending on the operation 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.

  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 a predetermined 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, fuel injection is performed at an appropriate time in the compression stroke, with the tumble control valve 12 basically closed, and the compression is increased. Ignition is performed at the time before 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. In a predetermined region on the high speed and high load side, as a normal homogeneous combustion operation, fuel injection is performed during the intake stroke with the tumble control valve 12 basically open, and before compression top dead center. Ignition is performed at the MBT point. 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, to promote the temperature rise and reduce the HC emission amount. Let it be an injection operation. In the top dead center injection operation, as shown in FIG. 1 described above, 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). Fuel injection is performed across the points. The ignition timing ADV is after compression top dead center (TDC), and is ignited at a timing delayed by 15 ° CA to 20 ° 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.

  By thus performing fuel injection across the compression top dead center and delaying the ignition timing from the compression top dead center, it becomes possible to achieve both a large retardation of the ignition timing and ensuring combustion stability. A sufficient increase in exhaust gas temperature and a reduction in HC emissions can be achieved.

  FIG. 8 shows combustion stability in the case of the present embodiment in which fuel injection is performed across the compression top dead center as described above, and in the case of conventional fuel injection in which fuel injection ends before the compression top dead center. This is a comparison of the retard limit of the ignition timing that is limited above the degree. That is, if the ignition timing is retarded as shown in the curve in the figure, the combustion stability deteriorates. Therefore, the ignition timing retardation is limited by the limit of the combustion stability, and a slight margin is expected in practical use. The position of the broken line is limited. Here, in the conventional fuel injection, the retardation is limited to the position of the broken line a with respect to the same combustion stability limit. On the other hand, in the present embodiment in which fuel injection is performed across the compression top dead center, it is possible to retard to the position of the broken line b.

  FIG. 9 shows the relationship between the ignition timing ADV and the exhaust temperature, and the exhaust temperature can be further increased by delaying the ignition timing ADV from the compression top dead center. The set point of the ignition timing ADV in this embodiment is set to a point as close as possible to the combustion stability limit, which is the limit at which the combustion stability deteriorates.

  FIG. 10 shows the relationship between the ignition timing ADV and the HC emission amount. By delaying the ignition timing ADV from the compression top dead center, the HC emission amount can be further reduced. That is, since ignition is performed in a state in which the air-fuel mixture is stratified, unburned fuel is reduced and HC emission is reduced. If the ignition timing ADV is set too late, the combustion stability is naturally deteriorated, but the injected fuel is diffused, so that HC tends to deteriorate as shown in the figure.

  FIG. 11 shows the relationship between the fuel injection timing IT (fuel injection start timing ITS), the ignition timing ADV, and the combustion stability, and the equal combustion stability using the fuel injection start timing ITS and the ignition timing ADV as parameters. The degree lines are drawn as contour lines. The line “IT = ADV” in the drawing is a line in which the injection start timing ITS and the ignition timing ADV are equal, and the upper side means that the ignition timing ADV is relatively late. An alternate long and short dash line m indicates a line giving a time difference until the spray reaches the spark plug 10. As shown in this figure, the combustion stability is highest when the fuel injection start timing ITS is near top dead center and the ignition timing ADV is delayed to some extent. The inside of the equal combustion stability line corresponding to the combustion stability limit where the combustion stability is the limit of the allowable level is a range where combustion can be established. In this embodiment, the ignition timing ADV is set so as to be the most retarded within this range, and the fuel injection start timing ITS is set corresponding to the ignition timing ADV.

  Next, FIGS. 12 and 13 show different embodiments of the internal combustion engine to which the present invention is applied. In this embodiment, in particular, the position of the fuel injection valve 15 is changed. As a so-called direct injection type, the fuel injection valve 15 is surrounded by a pair of intake valves 6 and a pair of exhaust valves 8. It is arrange | positioned in the center part of the chamber 5 ceiling surface, and the spark plug 10 is arrange | positioned adjacent to this. Fuel is injected from the fuel injection valve 15 at an angle close to vertical, more specifically, slightly inclined toward the spark plug 10, and a part of the spray is injected into the spark plug 10. Heading near the electrode. The top of the piston 3 is a concave surface that is loose as a whole. The intake port 7 is provided with a tumble control valve 12 for enhancing the tumble flow.

  Even in the internal combustion engine having such a configuration, the above-described top dead center injection operation is possible.

  Further, as shown in FIG. 14, instead of the tumble control valve 12, a known swirl control valve 41 that opens and closes only one intake port 7 is provided, and by closing this, a swirl flow is generated in the cylinder. The present invention is also applicable to the internal combustion engine configured as described above.

  In each of the above embodiments, an example in which a tumble control valve and a swirl control valve for strengthening a tumble flow and a swirl flow are provided as necessary has been described. However, the present invention provides such gas flow strengthening means. The present invention can be similarly applied to an internal combustion engine that does not include the engine.

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 ignition timing retardation limit of a present Example compared with the thing of the conventional type fuel injection. The characteristic view which shows the relationship between ignition timing and exhaust gas temperature. The characteristic view which shows the relationship between ignition timing and HC discharge | emission amount. The characteristic view which shows the relationship between fuel injection timing, ignition timing, and combustion stability. Sectional drawing which shows the Example from which a cylinder direct injection type spark ignition internal combustion engine differs. FIG. The top view which shows the Example which provided the swirl control valve.

Explanation of symbols

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

Claims (5)

  In a control device for a direct injection type spark ignition internal combustion engine that includes a fuel injection valve that directly injects fuel into a cylinder and includes an ignition plug, the fuel injection is performed at an injection start timing in a predetermined operating state. Is performed in a period straddling the compression top dead center so that the injection end timing is after the compression top dead center before the compression top dead center, and ignition is performed after the compression top dead center delayed from the injection start timing. A control device for an in-cylinder direct injection spark ignition internal combustion engine.   2. The direct injection spark ignition internal combustion engine according to claim 1, wherein when the exhaust gas temperature is required to be raised as a predetermined operating state, the fuel injection period and the ignition timing are controlled. Control device.   3. The control device for a direct injection type spark ignition internal combustion engine according to claim 1, wherein the ignition timing is a timing delayed by 15 ° CA to 20 ° CA from the injection start timing.   The control of the direct injection spark ignition internal combustion engine according to any one of claims 1 to 3, wherein a period before the compression top dead center and a period after the compression top dead center in the fuel injection period are substantially equal. apparatus. The control device for a direct injection spark ignition internal combustion engine according to any one of claims 1 to 4, wherein the average air-fuel ratio is substantially the stoichiometric air-fuel ratio.

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