JP2006250050A - In-cylinder direct injection spark ignition internal combustion engine controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the temperature of exhaust gases when an engine is cool by making compatible the largely spark-retarded angle of an ignition timing with the stability of combustion. <P>SOLUTION: When the engine completes warmup operation, normal stratified combustion operation and homogeneous combustion operation are performed. When the engine is cool, a fuel injection is performed on both sides of a top dead center so that, as a top dead center injection operation mode, an injection start timing ITS is positioned before the top dead center in a compression stroke and an injection end timing ITE is positioned after the top dead center. An ignition timing ADV is positioned after the top dead center. At the top dead center in the compression stroke, swirls and tumbles are attenuated and very small disturbance is activated. Since a change in the position of a piston is also small, stable combustion can be realized. Furthermore, since a part of the fuel is injected as an early injection I2 during the compression stroke or intake stroke before the main injections I1 on both sides of the top dead center, a combustion period is increased and the temperature of the exhaust gases are further increased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 includes a fuel injection valve that directly injects fuel into a cylinder, an ignition plug, and spray injected from the fuel injection valve when the piston is near top dead center. It is premised on an in-cylinder direct injection spark-ignition internal combustion engine that can reach the spark plug without any operation. The injection is performed in a period straddling 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, and after the compression top dead center delayed from the injection start time. In addition to performing ignition, a part of the fuel is injected as an early injection prior to the main injection in a period across the compression top dead center.

  FIG. 1 exemplifies the fuel injection period and ignition timing in the top dead center injection operation mode of the present invention together with the in-cylinder pressure change. As shown in the figure, main injection I1 and early injection I2 preceding this are performed. However, in the present invention, combustion is basically established by the main injection I1. In the main injection I1, 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). 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 significantly increased by a large retardation of the ignition timing, and the HC emission amount is reduced.

  Here, as a basic property of the internal combustion engine, in order to reduce the generation of HC, the spray injected near the compression top dead center as the main injection I1 collides with the combustion chamber wall surface (including the piston top surface). It is desirable to ignite before reaching the spark plug and before the spray reaches the combustion chamber wall surface. That is, it is desirable in terms of HC reduction that the spray burns without adhering anywhere on the wall surface of the combustion chamber. However, when the spray burns without interfering with the wall surface of the combustion chamber in this way, the exhaust gas temperature is lower than when the combustion is completed in a relatively short time due to the energy of the spray itself and the combustion proceeds slowly. Become. In other words, by retarding the ignition timing from the compression top dead center, the exhaust gas temperature becomes sufficiently high, but if the spray burns without adhering anywhere on the wall surface of the combustion chamber, Since the process is completed in a short time, the exhaust gas temperature cannot be maximized.

  Therefore, in the present invention, as shown in FIG. 1, a part of the fuel is injected as the early injection I2 prior to the main injection I1 in the period across the compression top dead center. This early injection I2 may be performed during the intake stroke before the bottom dead center, or may be performed during the compression stroke, as shown.

  Since the fuel injected as the early injection I2 in the intake stroke or the compression stroke is diffused in the cylinder before the injection timing of the main injection I1 in this way, when the combustion is started by being ignited by the spray by the main injection I1. In addition, the combustion chamber as a whole burns relatively slowly. Therefore, a higher exhaust gas temperature can be obtained.

  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. In particular, exhaust gas temperature can be maximized by supplying a part of the fuel into the cylinder in advance as early injection.

  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 (see FIG. 7). 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. .

  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) on the plan view, and is arranged obliquely downward on the cross-sectional view of FIG. However, the direction of the spray is slightly different from the center line of the fuel injection valve 15 itself, and the spray does not collide with the top surface of the piston 3 even when the piston 3 is near the top dead center. The fuel is injected along a plane orthogonal to the cylinder axis so as to pass through the space. In particular, as shown in FIGS. 5 and 6, the shape of the spray f is such that it has a flat fan-shaped spray shape extending substantially along a plane orthogonal to the cylinder axis, and the inner wall surface of the combustion chamber 5 (the top surface of the piston 3 So that the spray reaches the vicinity of the spark plug 10 without colliding anywhere (including a portion of the spray reaches the vicinity of the spark plug 10 at a timing at which all the spray does not collide anywhere on the inner wall surface of the combustion chamber). It has become. In order to realize such a spray shape, a multi-hole fuel injection valve having a large number of fine injection holes is used as the fuel injection valve 15.

  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 fuel that has been adjusted to an appropriate pressure by the fuel pump 31 and the pressure regulator 32 via a 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, and ignition is performed at a time before compression top dead center. In this operation mode, fuel injection always ends before compression top dead center. Here, stratified combustion with an average air-fuel ratio lean is realized.

  In a predetermined region on the high speed and high load side after completion of warm-up, fuel injection is performed during the intake stroke as a normal homogeneous combustion operation mode, and ignition is performed at the MBT point before 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. 1 described above, the main injection I1 and the early injection I2 preceding this are performed. In the main injection I1, the injection start timing ITS is before the compression top dead center (TDC), the injection end timing ITE is after the compression top dead center (TDC), and 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 by combining the early injection I2.

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

  The early injection I2 injects a part of fuel during the compression stroke or the intake stroke prior to the main injection I1, and the fuel injected as the early injection I2 is injected before the injection timing of the main injection I1. It diffuses into the cylinder (when it is injected during the compression stroke, it becomes a mass of air-fuel mixture diffused to some extent, and when it is injected during the intake stroke, it becomes a homogeneous lean air-fuel mixture). And since the combustion by the fuel of this early injection I2 is continued after being ignited by the spray by the main injection I1 and starting combustion, the combustion period becomes longer as a whole, and the exhaust gas temperature can be higher.

  FIG. 8 shows the heat generation characteristics when the entire amount of fuel is injected only by the main injection I1 as in (1) and when the early injection I2 is added prior to the main injection I1 as in (2). As shown in the figure, in the case of only the main injection I1, as shown by the solid line, the combustion is completed in a short period of time. On the other hand, when the early injection I2 is added, as shown by the broken line, the combustion period becomes longer, and accordingly, the exhaust gas temperature is increased. This is an example in which the early injection I2 is performed during the compression stroke.

  FIG. 9 shows (a) combustion stability (variation σPi of in-cylinder pressure Pi) and (b) exhaust gas when only the main injection I1 (solid line) and when the early injection I2 is added (broken line). This is a comparison of temperature characteristics. The in-cylinder pressure variation σPi indicating deterioration in combustion stability rapidly increases at a certain point (that is, combustion instability) as the ignition timing is retarded, but as shown in FIG. In the case (broken line), combustion becomes more unstable on the more advanced side. In other words, the retard of the ignition timing is limited when the early injection I2 is added. This is for the reason described above. However, as shown in (b), the exhaust gas temperature characteristics are generally higher when the early injection I2 is added (broken line) than when only the main injection I1 (solid line). Assuming that the engine is operated at each stability limit, the exhaust gas temperatures at that time are T1 and T2, respectively, and the case where the early injection I2 is added (T2) is the case where only the main injection I1 (T1) ). Therefore, the catalytic converter 22 can be activated earlier when cold.

  Next, FIG. 10 shows the HC emission amount of the internal combustion engine (so-called engine-out HC) when the early injection I2 is performed during the intake stroke (solid line) and when it is performed during the compression stroke (broken line). As shown in the drawing, as shown in the drawing, the HC discharge amount is more advantageous during the compression stroke. This is considered that when fuel is injected during the intake stroke, HC generation due to clevis or the like in the combustion chamber 5 increases.

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 change of the characteristic of the heat generation by the presence or absence of early injection. The characteristic view which shows the characteristic of combustion stability and exhaust gas temperature by this invention. The characteristic view which shows the difference in HC discharge | emission amount by the time of early injection.

Explanation of symbols

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

Claims (7)

  A fuel injection valve that directly injects fuel into the cylinder and an ignition plug, and when the piston is near top dead center, the spray injected from the fuel injection valve ignites without colliding with the wall of the combustion chamber. In a control device for an in-cylinder direct injection spark ignition internal combustion engine that can reach the plug, when the exhaust gas temperature needs to be raised, the fuel injection is performed as the top dead center injection operation mode, and the injection start timing is compressed. Before the dead center, the injection end timing is performed after the compression top dead center so that the injection end timing is after the compression top dead center, and ignition is performed after the compression top dead center delayed from the injection start timing. A control apparatus for an in-cylinder direct injection spark ignition internal combustion engine, wherein a part of fuel is injected as an early injection prior to a main injection in a period spanning a point.   The control device for a direct injection spark ignition internal combustion engine according to claim 1, wherein the early injection is performed during a compression stroke.   The control device for a direct injection type spark ignition internal combustion engine according to claim 1, wherein the early injection is performed during an intake stroke.   4. The fuel injection valve according to claim 1, wherein the fuel injection valve is disposed at a side portion of the combustion chamber, and is configured to inject fuel substantially along a plane perpendicular to the cylinder axis. A control device for an in-cylinder direct injection spark ignition internal combustion engine.   5. The control device for a direct injection type spark ignition internal combustion engine according to claim 4, wherein the fuel injection valve has a flat fan-shaped spray shape extending substantially along the plane.   6. The control of an in-cylinder direct injection spark ignition internal combustion engine according to claim 1, wherein the fuel injection valve is a multi-hole type fuel injection valve having a large number of fine injection holes. apparatus. The control device for a direct injection spark ignition internal combustion engine according to any one of claims 1 to 6, wherein the ignition is performed by the spark plug before the spray reaches the wall surface of the combustion chamber.

Images