JP4428226B2 - 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 relates to 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. Is requested as the top dead center injection operation mode, and the fuel injection is performed in a period spanning the compression top dead center so that the injection start timing is before the compression top dead center and the injection end timing is after the compression top dead center. And ignition is performed after compression top dead center delayed from the injection start timing. In particular, the top dead center injection operation mode is not continued until the catalyst temperature reaches the catalyst activation temperature, but before the catalyst temperature reaches the catalyst activation temperature, it depends on the inlet temperature and the internal temperature of the catalytic converter. The release is made based on the determination of the temperature state of the catalytic converter.

  FIG. 1 illustrates the fuel injection period and ignition timing in the top dead center injection operation mode of the present invention together with the change in the in-cylinder pressure. The injection start timing ITS is before the compression top dead center (TDC), and the injection end timing ITE is After 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 in which the ignition timing is greatly retarded as described above, the exhaust gas temperature is very high compared to the conventional technology such as Patent Document 1, so that the catalytic converter has the temperature In the process of rising, the temperature gradient inside the catalytic converter tends to become very steep. That is, there is a concern that only the upstream portion such as the monolithic ceramic catalyst carrier rapidly becomes high in temperature and the thermal strain increases. In addition, since the exhaust temperature becomes very high, even if it is determined that the catalyst temperature has reached the activation temperature and the top dead center injection operation mode is stopped, the heat capacity of the exhaust system parts upstream of the catalytic converter and the catalyst itself The internal temperature of the catalytic converter continues to rise due to reaction heat or the like, and the internal temperature of the catalytic converter may overshoot to the catalyst deterioration temperature.

Therefore, in the present invention, the top dead center injection operation mode is not continued until the catalyst temperature reaches the catalyst activation temperature, and the catalyst according to the inlet temperature and the internal temperature of the catalytic converter before the catalyst temperature reaches the catalyst activation temperature. The release is made based on the determination of the temperature state of the converter.

Further, in one aspect of the present invention, the internal temperature as above fill port temperature is higher releases the TDC injection operation mode at a low stage.

Thus, by determining the timing of releasing the top dead center injection operation mode from the inlet temperature and the internal temperature of the catalytic converter, it is possible to avoid excessive overshoot of the internal temperature and occurrence of an excessive thermal gradient.

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, and when the internal combustion engine is cold, the exhaust gas temperature is raised and the catalyst is activated early. The amount of HC emission can be reduced. Since the top dead center injection operation mode is canceled at an appropriate timing before the catalyst temperature reaches the catalyst activation temperature, thermal deterioration due to excessive overshoot of the catalyst temperature, damage to the catalyst carrier due to extreme temperature gradient, etc. Can be avoided.

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

5 and 6 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, and FIG. Shows the system configuration of the entire organization as a reference example .

  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. That is, the fuel injection valve 15 is located on the side of the combustion chamber 5 on the intake valve 6 side, and is disposed so as to inject fuel along a direction orthogonal to a piston pin (not shown) on the plan view. In the cross-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 reference example is, for example, an in-line four-cylinder engine, and is used for exhaust purification using a monolithic ceramic catalyst carrier in the exhaust passage 21 to which the exhaust port 9 of each cylinder is connected. A catalytic converter 22 is provided, and an air-fuel ratio sensor 23 such as an oxygen sensor is disposed upstream thereof. 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. In this embodiment, the fuel pressure is always kept constant. The ignition plug 10 of each cylinder is connected to an ignition coil 34.

  The fuel injection timing, injection amount, injection rate, 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. Furthermore, in this embodiment, in order to determine the temperature state of the catalytic converter 22, a catalyst inlet temperature sensor 38 disposed at the inlet portion of the catalytic converter 22 is provided.

  In the internal combustion engine configured as described above, normal stratified combustion operation and homogeneous combustion operation are performed after the warm-up is completed.

  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, in the state where the warm-up of the internal combustion engine is not completed, the top dead center injection operation mode is basically set in order to activate the catalytic converter 22, that is, promote the temperature rise and reduce the HC emission amount. . In this top dead center injection operation mode, 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 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. 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, since the exhaust gas temperature is obtained extremely high, the catalytic converter 22 is rapidly heated from the upstream side, and the thermal distortion of the catalytic converter 22 or excessive temperature rise occurs. There are concerns. Therefore, in the reference example , the mode is switched while monitoring the temperature state of the catalytic converter 22 by the processing as shown in FIG.

  First, in step 1, the inlet temperature T of the catalytic converter 22 detected by the catalyst inlet temperature sensor 38 is read, and the rate of change, that is, the amount of change dT per unit time is obtained. Next, whether or not the catalyst is active in step 2 is determined from, for example, the cooling water temperature at the start of the engine or the catalyst inlet temperature T at the start. If the catalyst is already in an active state as in warm-up restart, the routine proceeds to step 5 and the above-described normal stratified combustion operation or homogeneous combustion operation is performed.

  If the catalyst is in an inactive state as in the cold start, the process proceeds to step 3 to execute the above-described top dead center injection operation mode. As a result, the exhaust temperature rises rapidly.

  Thereafter, in step 4, based on the catalyst inlet temperature T and its change rate dT, it is determined whether or not the temperature state of the catalytic converter 22 has reached a predetermined stage before the catalyst is fully activated. Specifically, from the catalyst inlet temperature T and the change rate dT, it is repeatedly determined whether the region is in the permission condition or the prohibition condition of the characteristic as shown in FIG. The point injection operation mode is continued. When the prohibited condition region is entered, the process proceeds from step 4 to step 5 to cancel the top dead center injection operation mode and shift to normal control. The above-mentioned prohibition condition region is set so that the catalyst temperature that rises later even after the release of the top dead center injection operation mode does not excessively overshoot beyond the full activation temperature. The higher the dT, the higher the dead center injection operation mode is canceled when the catalyst inlet temperature T is lower. Accordingly, excessive overshoot of the catalyst temperature and thermal distortion due to an extreme temperature gradient are prevented.

  Hereinafter, the temperature change of the catalytic converter 22 will be described. FIG. 10 shows, as an example, changes in the inlet temperature (approximately equal to the exhaust gas temperature) and the internal temperature of the catalytic converter after the cold start, and the broken line shows the characteristics when the normal combustion operation is continued after the start. Indicates the characteristics when the top dead center injection operation mode is continued after the start. As shown in the figure, in the top dead center injection operation mode, the exhaust temperature (inlet temperature) rises sharply after startup, and the time required until the internal temperature reaches the catalyst activation temperature (complete activation temperature) T1 is greatly reduced. The However, paying attention to the temperature difference between the inlet temperature and the internal temperature (in other words, the temperature gradient of the catalyst carrier), the temperature difference ΔT when the internal temperature reaches the catalyst activation temperature T1 is the top dead center injection indicated by the solid line. The rapid heating in the operation mode is larger than the gentle heating shown by the broken line. That is, when the temperature is rapidly increased in the top dead center injection operation mode, the thermal distortion generally tends to increase.

  FIG. 11 shows a comparative example when the top dead center injection operation mode is canceled when the internal temperature reaches the catalyst activation temperature T1. In this case, even after canceling the top dead center injection operation mode, the internal temperature of the catalytic converter continues to rise due to the heat capacity of the exhaust system components upstream of the catalytic converter, the reaction heat of the catalyst itself, etc. The internal temperature may overshoot to the catalyst deterioration temperature.

On the other hand, FIG. 12 shows the temperature change of the catalytic converter in the case of the reference example , and the top dead center injection operation mode is canceled before the internal temperature reaches the catalyst activation temperature T1. At this time, the internal temperature is, for example, temperature T2 lower than the catalyst activation temperature T1, and after the top dead center injection operation mode is released, the temperature further rises from this temperature T2, but does not reach the catalyst deterioration temperature. Further, since the inlet temperature quickly decreases with the release of the top dead center injection operation mode, the temperature difference ΔT between the internal temperature and the inlet temperature when the internal temperature reaches the catalyst activation temperature T1 is shown in FIG. It becomes smaller than the case of FIG.

In the above reference example , the inlet temperature T of the catalytic converter 22 is directly detected by the catalyst inlet temperature sensor 38. However, since the inlet temperature T correlates with the intake air amount of the internal combustion engine, this intake air amount. It is also possible to estimate the inlet temperature T based on.

Next, FIGS. 13 to 15 show a first embodiment of the present invention. In this embodiment, in order to determine the temperature state of the catalytic converter 22, as shown in FIG. In addition to the catalyst inlet temperature sensor 38 disposed at the inlet portion 22, a catalyst temperature sensor 39 disposed at the center in the longitudinal direction of the monolith ceramic catalyst carrier is provided. Therefore, the internal temperature TC of the catalytic converter 22 is detected together with the catalyst inlet temperature T.

  In this embodiment, the mode is switched while monitoring the temperature state of the catalytic converter 22 by the processing as shown in FIG.

  First, in step 1, the inlet temperature T of the catalytic converter 22 detected by the catalyst inlet temperature sensor 38 and the internal temperature TC of the catalytic converter 22 detected by the catalyst temperature sensor 39 are read. Next, whether or not the catalyst is active in step 2 is determined from, for example, the internal temperature TC at the time of engine start, the cooling water temperature, or the like. If the catalyst is already in an active state as in warm-up restart, the routine proceeds to step 5 and the above-described normal stratified combustion operation or homogeneous combustion operation is performed.

  If the catalyst is in an inactive state as in the cold start, the process proceeds to step 3 to execute the above-described top dead center injection operation mode. As a result, the exhaust temperature rises rapidly.

  Thereafter, in step 4, it is determined whether the temperature state of the catalytic converter 22 has reached a predetermined stage before the catalyst is fully activated based on the catalyst inlet temperature T and the internal temperature TC. Specifically, from the catalyst inlet temperature T and the internal temperature TC, it is repeatedly determined whether the region is in the permission condition or the prohibition condition of the characteristic as shown in FIG. The point injection operation mode is continued. When the prohibited condition region is entered, the process proceeds from step 4 to step 5 to cancel the top dead center injection operation mode and shift to normal control. The above-mentioned prohibition condition region is set so that the catalyst temperature that rises after the release of the top dead center injection operation mode does not excessively overshoot beyond the full activation temperature. The higher the inlet temperature T is, the higher the dead center injection operation mode is canceled when the internal temperature TC is lower. Accordingly, excessive overshoot of the catalyst temperature and thermal distortion due to an extreme temperature gradient are prevented.

  In the above embodiment, the inlet temperature T of the catalytic converter 22 is directly detected by the catalyst inlet temperature sensor 38, but the inlet temperature T correlates with the intake air amount of the internal combustion engine. It is also possible to estimate the inlet temperature T based on.

  In the above embodiment, the internal temperature TC of the catalytic converter 22 is directly detected by the catalyst temperature sensor 39. However, the internal temperature is determined from other parameters, for example, the oxygen storage capacity of the catalytic converter 22 correlated with the catalyst temperature. It is also possible to estimate TC. Specifically, as shown in FIG. 16, in addition to the upstream air-fuel ratio sensor 23 upstream of the catalytic converter 22, a downstream air-fuel ratio sensor 40 is provided downstream of the catalytic converter 22. Then, as shown in the upper part of FIG. 17, air-fuel ratio control is performed so that the air-fuel ratio (exhaust air-fuel ratio) of the internal combustion engine oscillates with an appropriate period and amplitude. For this, a general air-fuel ratio feedback control technique can be used. With respect to this change in air-fuel ratio, the air-fuel ratio detected by the upstream air-fuel ratio sensor 23 directly reflects the change in the air-fuel ratio of the engine. On the other hand, the detected air-fuel ratio of the downstream air-fuel ratio sensor 40 is the same as the signal of the upstream air-fuel ratio sensor 23 because the oxygen storage capacity is low when the catalytic converter 22 is inactive as shown in the lower part of FIG. However, as the temperature of the catalytic converter 22 rises, the oxygen storage capacity increases, and as shown in the figure, the cycle is long and the amplitude is small. Therefore, it can be detected from the relationship between the two that the catalyst has reached the activation start temperature before the complete activation.

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 flowchart which shows the mode switching process at the time of a start. The characteristic view which shows the permission / prohibition area | region of top dead center injection operation mode. The characteristic view which shows the change of the catalyst inlet_port | entrance temperature and internal temperature at the time of continuing a top dead center injection operation mode compared with the case where a normal combustion operation is continued. The characteristic view which shows the temperature change at the time of canceling | releases a top dead center injection operation mode when internal temperature reaches catalyst activation temperature. The characteristic view which shows the change of the catalyst inlet_port | entrance temperature and internal temperature by a reference example . Structure explanatory drawing which shows the 1st example. The flowchart which shows the process of this 1st Example. The characteristic view which shows the permission / prohibition area | region in the case of this 1st Example. Structure explanatory drawing which shows 2nd Example. The characteristic view which shows the detection air fuel ratio of the upstream air fuel ratio sensor in this 2nd Example, and the detection air fuel ratio of a downstream air fuel ratio sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Piston 5 ... Combustion chamber 10 ... Spark plug 15 ... Fuel injection valve 23 ... (Upstream side) Air fuel ratio sensor 38 ... Catalyst inlet temperature sensor 39 ... Catalyst temperature sensor 40 ... Downstream air fuel ratio sensor

Claims (5)

In 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, the temperature of a catalytic converter provided in an exhaust system is required to be increased. Sometimes, as a top dead center injection operation mode, fuel injection is performed in a period across 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 Ignition is performed after the compression top dead center delayed from the injection start timing, and the top dead center is determined based on the determination of the temperature state of the catalytic converter based on the inlet temperature and the internal temperature of the catalytic converter before the catalyst temperature reaches the catalytic activation temperature. A control apparatus for an in-cylinder direct injection spark ignition internal combustion engine, wherein the point injection operation mode is canceled. 2. The control apparatus for a direct injection type spark ignition internal combustion engine according to claim 1, wherein the top dead center injection operation mode is canceled when the internal temperature is lower as the inlet temperature is higher. 3. The control apparatus for a direct injection spark ignition internal combustion engine according to claim 1, wherein the inlet temperature is estimated based on an intake air amount of the internal combustion engine. 4. The control apparatus for a direct injection spark ignition internal combustion engine according to claim 1, wherein the internal temperature is estimated from an oxygen storage capacity of a catalytic converter correlated with a catalyst temperature. An upstream air-fuel ratio detecting means provided upstream of the catalytic converter and a downstream air-fuel ratio detecting means provided downstream; a change in detection signal of the upstream air-fuel ratio detecting means and downstream air-fuel ratio detection; 5. The control apparatus for a direct injection spark ignition internal combustion engine according to claim 4, wherein the oxygen storage capacity is estimated from a relationship with a change in a detection signal of the means.

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