Control apparatus for cylinder fuel injection internal combustion engines

Abstract

A control apparatus for a cylinder fuel injection internal combustion engine in which a compression stroke injection mode for carrying out fuel injection mainly in a compression stroke and a suction stroke injection mode for carrying out fuel injection mainly in a suction stroke can be selected in accordance with the operational condition of the engine. The apparatus aiming at enabling a suitable suction correcting amount to be set for each operational mode of the engine and the improvement of drivability thereby being improved.

Description

This application claims the benefit under 35 U.S.C. § 371 of prior PCT International Application No. PCT/JP97/01441, which has an International filing data of Apr. 24, 1997, which designated the United States of America, the entire contents of which are hereby incorporated by references.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a control unit for in-cylinder injection internal combustion engine which can select, according to an engine operation state, a compression stroke injection mode for mainly injecting fuel at a compression stroke and an intake stroke injection mode for mainly injecting fuel at an intake stroke; and, in particular, to a control unit for in-cylinder injection internal combustion engine which can optimally correct an intake amount.

2. Background Art

A throttle valve is installed in an intake passage of an engine such as an internal combustion engine. There has been developed a configuration of an intake system in which a bypass passage bypassing the throttle-valve-installed portion is formed such that its both end portions communicate with the intake passage, and the bypass passage is equipped with a bypass valve.

Commonly employed as such a bypass valve is, for example, a bypass valve for idle speed control which is used for adjusting the intake amount so that the engine can maintain a predetermined idling rotational speed.

Independently of a throttle valve whose opening degree is adjusted in response to a driver's operation for stepping on an accelerator pedal, the opening degree of the idle speed control bypass valve is appropriately adjusted, while feeding back the engine rotational speed, in order to keep the engine rotational speed at a predetermined idle rotational speed, and independently of the driver's accelerator pedal operation, the intake amount is adjusted so as to maintain the idle rotational speed.

Also, there has been developed a configuration of an intake system in which, separately from the bypass passage for idle speed control and the bypass valve, a bypass passage for bypassing the throttle-valve-installed portion of the intake passage is formed so as to be used for controlling the air/fuel ratio of the air/fuel mixture supplied to a combustion chamber not only upon idling, and this bypass passage is equipped with a bypass valve [predetermined relationship (between operation state and intake correction amount)] according to these data.

Namely, as shown in FIG. 5, a target engine load Pe (target Pe) is initially set, according to a map, from a throttle opening degree θth detected by the throttle sensor or the engine rotational speed Ne based on the output of the non-depicted accelerator opening sensor and the information detected by the crank angle sensor (block B1) On the other hand, based on the information from the air conditioner switch, when the air conditioner is on, an air-conditioner-related correction amount ΔPeac is set from the engine rotational speed Ne according to a map (block B2). Based on the information from the power steering switch, when the power steering is on, a power-steering-related correction amount ΔPeps is set from the engine rotational speed Ne according to a map (block B3). Based on the information from the inhibitor switch, upon starting, an inhibitor-related correction amount ΔPeinh is set from the engine rotational speed Ne according to a map (block B4).

Also, though not depicted, for the shift position sensor 121 and the atmospheric pressure sensor 122, correction amounts corresponding to their respective parameters are set.

Then, according to these specific correction amounts ΔPeac, ΔPeps, ΔPeinh, and the like, the target Pe is appropriately corrected. Thus corrected target Pe is appropriately filtered through a switch S1 (block B5), and a control amount Pos concerning a valve opening degree corresponding to a required air amount (or target intake air amount) Q is set, according to a map, from thus obtained target Pe and the engine rotational speed Ne.

As shown in block B7, in order to set the control amount Pos, from a plurality of maps, the one corresponding to the engine operation state is selectively used, and a signal is outputted through switches S2 and S3 in response to the engine operation state. Here, maps are provided for three modes, as the engine operation states, comprising the later lean mode that yields the leanest burn, the earlier lean mode that yields the next leanest burn thereto, and an EGR-actuated state in the stoichiometric operation mode; and the required air amount is set only in these modes.

In the case where the idle operation state is established, by a switch S4, a control amount #1ABV valve in this case) for a required air amount (or target intake air amount) #1ABVQ based on feedback of the engine rotational speed is set as shown in block B8.

The functional section for setting the amount corresponding to the required air amount Q, #1ABVQ, through the above-mentioned blocks B7 and B8 is equivalent to the required air amount setting means (intake correction amount setting means) 110.

In response to thus obtained control amount Pos or #1ABVPos, setting of the opening position of the air bypass valve 6 or duty cycle (block B10) and setting of the air bypass valve 14 (block B11) are effected, whereby the air bypass valves 6 and 14 are controlled so as to attain predetermined states.

Meanwhile, in the compression stroke injection mode (later lean) in the in-cylinder injection engine, since ultra-lean burning is effected, the air/fuel ratio is set very high, whereby the intake air amount is quite large in relation to the engine-generated torque. Consequently, the intake amount is corrected in a region where the magnitude of intake vacuum is relatively low. In the intake stroke injection mode, by contrast, since operation is performed under the earlier lean mode or stoichiometric mode with a relatively high air/fuel ratio, the intake air amount is not relatively large in relation to the engine-generated torque, whereby the intake amount is corrected in a region where the magnitude of intake vacuum is relatively large.

For example, the solid line shown in FIG. 2 indicates intake air amount Q in relation to intake opening area S. As depicted, the intake air amount control (intake correction amount control) in the compression stroke injection mode (later lean) is performed in a region where the intake opening area S is relatively large, whereas the intake air amount control (intake correction amount control) in the intake stroke injection mode is performed in a region where the intake opening area S is relatively small. Here, the intake opening area S corresponds to the engine load state and is determined according to the opening degrees of the throttle valve (intake throttle valve) 15 and the ABVs (intake amount correcting means) 6 and 14.

In FIG. 2, point X1 indicates a point where the intake opening area S and the intake air amount Q correspond to each other when engine torque TA is generated in the intake stroke injection mode, whereas point X2 indicates a point where the intake opening area S and the intake air amount Q correspond to each other when engine torque TA substantially the same as that at point X1 is generated in the compression stroke injection mode.

As depicted, when the intake opening area S is increased by a predetermined amount S1 at the point X1 in the intake stroke injection mode, the intake correction amount increases by Q1. By contrast, when the intake opening area S is increased by the predetermined amount S1 at the point X2 in the compression stroke injection mode as in the case of the point X1, the intake correction amount increases by Q2. This intake correction amount Q2 is smaller than the intake correction amount Q1 in the case of the point X1.

The intake amount control in the intake stroke injection mode is effected in a region where the intake opening area S is relatively small. Since this region is an area where the magnitude of intake vacuum downstream the throttle valve 15 is relatively large, the intake opening area S and the intake air amount Q increase substantially linearly. By contrast, the intake amount control in the compression stroke injection mode is effected in a region where the intake opening area S is relatively large. Since this region is an area where the magnitude of intake vacuum downstream the throttle valve 15 is relatively small, the intake opening area S and the intake air amount Q deviate from their linear relationship of increase, whereby the intake air amount Q does not increase so much as the intake opening area S increases. Here, the dotted line in FIG. 2 indicates a case where the intake opening area S and the intake air amount Q maintain a linear relationship therebetween.

Here, in the case where the intake opening area S and the control amount Pos concerning the valve opening degree are substantially in proportion to each other, in order to increase the intake opening area S by a predetermined amount S1, it is sufficient for the control amount Pos to be increased by a correction control amount P1. In the case where the intake opening area S and the control amount Pos concerning the valve opening degree are not in proportion to each other, an approximate expression of their relationship or the like may be used to compute a correction control amount P2 from the intake opening area S, and the control amount Pos may be increased by thus computed correction control amount P2.

Thus, since the intake air amount changing in relation to the intake opening area varies; when the same map (relationship between the engine operation state and the control amount Pos) is used for the control amount concerning the valve opening degree for adjusting the intake opening area in both intake stroke injection mode and compression stroke injection mode, an optimal intake correction amount may not be set for each operation mode, thus deteriorating drivability.

Therefore, in this apparatus, different maps (relationships between the engine operation state and control amount Pos) are respectively set for the intake stroke injection mode and the compression stroke injection mode, so that the intake correction control is performed according to the map for each mode.

Here, different maps (relationships) may be set respectively for the intake stroke injection mode and the compression stroke injection mode concerning not only the relationship between the engine operation state (engine rotational speed Ne and engine load information Pe in particular) and the control amount Pos, but also correction amounts based on other data, i.e., those from the shift position sensor 121, atmospheric pressure sensor 122, air conditioner switch 123, power steering switch 124, idle switch 38, and the like, so as to perform the intake correction control.

For example, FIG. 3 shows a state of control for the idle speed Ne effected when the air conditioner switch 123 is turned on from its off state. Here, the corresponding intake amount is adjusted from Q1 to Q3 in the case of the earlier lean (intake stroke injection), whereby the idle speed Ne is controlled so as to increase from Ni1 to Ni2. In the later lean (compression stroke injection), on the other hand, the intake amount is adjusted from Q2 to Q4, whereby the idle speed Ne is controlled so as to increase from Nil to Ni2.

As depicted, between the intake stroke injection mode and the compression stroke injection mode, not only the basic intake amount varies but also the intake correction amount differs, i.e., becomes α and β respectively in the intake stroke injection mode and the compression stroke injection mode. Accordingly, for the intake correction amount control based on the air conditioner switch information, it is preferred that different maps (relationships) be set respectively for the intake stroke injection mode and the compression stroke injection mode.

As a method other than that mentioned above, a common intake correction amount may be set among the individual operation modes, and a mode-related coefficient (gain) may be set for each mode, so that thus set intake correction amount is adjusted in terms of gain by its mode-related coefficient, thus setting a final intake correction amount (used for control).

In the following, with reference to FIG. 5, respective controls for the injector, ignition coil, and EGR will be explained.

In order to drive the injector, it is necessary to set the injection starting timing and injection terminating timing of the injector. Here, an injector driving time Tinj and the injection terminating timing of the injector are set, and based thereon, as the injection starting timing of the injector is counted backward, the injector driving timing is determined. These settings are effected by the ECU 16 according to the engine operation state.

In order to set the injector driving time Tinj, an air/fuel ratio is initially set (block B12), according to a map, from the corrected target Pe after filtering (block B6) and the engine rotational speed Ne. Also, in this case, different setting maps are provided for four modes comprising the EGR-actuated state in the later lean mode, EGR-stopped state in the later lean mode, earlier lean mode, and open-loop mode; and the one corresponding to the engine operation mode is selectively used.

From thus obtained air/fuel ratio A/F and an intake amount Qpb detected by the air flow sensor, the injector driving time Tinj is computed (block B13).

This injector driving time Tinj is corrected in terms of unequal injector ratios among cylinders (block B14) and dead times among cylinders (block B15). On the other hand, a deceleration injection time TDEC is computed from the target Pe and the engine rotational speed Ne (block B16). When the operation is in both decelerated state and later lean, of the injector driving time Tinj obtained at the block B13 and the deceleration injection time TDEC, the smaller value is selected through a switch S5 (block B17) and is determined as the injector driving time.

Also, since the air/fuel ratio A/F changes as the above-mentioned intake air amount is corrected, the injector driving time is corrected as the intake air amount is corrected, so as to attain a constant air/fuel ratio A/F, thereby preventing exhaust gas performances from deteriorating.

Also, the injection terminating timing of the injector is set (block B18), according to a map, from the corrected target Pe after filtering (block B6) and the engine rotational speed Ne. In this case, different setting maps are provided for four modes comprising the EGR-actuated state in the later lean mode, EGR-stopped state in the later lean mode, earlier lean mode, and open-loop or stoichiometric feedback operation mode; and the one corresponding to the engine operation mode is selectively used.

In the case of later lean mode, thus obtained injection terminating timing is corrected in terms of water temperature so as to yield an injection terminating timing.

Based on thus obtained injector driving time Tinj and injection terminating timing, the injector is driven.

Also, the ignition timing of the spark plug effected by the ignition coil is set (block B20), according to a map, from the corrected target Pe after filtering (block B6) and the engine rotational speed Ne. In this case, different setting maps are provided for five modes comprising the EGR-actuated state in the later lean mode, EGR-stopped state in the later lean mode, earlier lean mode, EGR-actuated state in stoichiometric feedback operation, and EGR-stopped state in open-loop or stoichiometric feedback operation. Thus obtained ignition timing is subjected to various kinds of retard corrections (block B 21), and the ignition coil is controlled on the basis thereof.

Also, the flow rate of the EGR is set (block B22), according to a map, from the corrected target Pe after filtering (block B6) and the engine rotational speed Ne. In this case, the setting maps are provided for four modes comprising the later lean mode in the D range, later lean mode in the N range, stoichiometric feedback operation mode in the D range, and stoichiometric feedback operation mode in the N range.

Thus obtained flow rate of the EGR is corrected in terms of water temperature (block B23), and a control amount (duty cycle) corresponding to the opening degree is set (block B24), so as to control the flow rate of the EGR. Here, for the water temperature correction (block B23), maps corresponding to engine operation states (two modes comprising the later lean mode and stoichiometric feedback operation mode here) are used.

The control unit for in-cylinder injection internal combustion engine as an embodiment of the present invention sets different maps (relationships between engine operation state and control amount Pos) respectively for the intake stroke injection mode and compression stroke injection mode, and the intake correction amount is controlled on the basis thereof, whereby the intake correction amount can be optimally corrected in each operation mode, thus improving drivability in each operation mode.

Also, as different maps (relationships) are set respectively for the intake stroke injection mode and the compression stroke injection mode concerning not only the relationship between the engine operation state (engine rotational speed Ne and engine load information Pe in particular) and the control amount Pos, but also correction amounts based on other data, i.e., those from the shift position sensor 121, atmospheric pressure sensor 122, air conditioner switch 123, power steering switch 124, idle switch 38, and the like, so as to perform the intake correction control; the intake correction amount can be optimally corrected in each operation mode, thus improving drivability in each operation mode as well.

Such a technique for setting different maps (relationships) respectively for the intake stroke injection mode and compression stroke injection mode is quite effectively employed upon idling operation of an engine having a high intake-controlling effect in particular.

Though the above-mentioned embodiment explains a case where the intake air amount is corrected by use of bypass valves, similar effects can also be obtained when such a technique is applied to an electric-motor-driven throttle valve which is driven by an electric motor such as that mentioned above.

Capability of Exploitation in Industry

An appropriate intake amount correction can be effected for each operation mode such as compression stroke injection mode and intake stroke injection mode in an in-cylinder injection internal combustion engine, thus allowing drivability to improve in the in-cylinder injection internal combustion engine. Consequently, the present invention is suitable for an engine for a vehicle such as automobile. It can simultaneously satisfy various requirements for a vehicle engine such as improvement in drivability due to stable burning, reduction of operation cost due to lower fuel consumption, environmental protection due to acceleration of exhaust gas purification, and the like, thus being quite useful.

Claims

1. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and is adapted to select, according to an operation state of said internal combustion engine, a compression stroke injection mode for mainly injecting fuel at a compression stroke and an intake stroke injection mode for mainly injecting fuel at an intake stroke,

said control unit comprising:

load correlation value detecting means for detecting a load correlation value of said internal combustion engine;

rotational speed detecting means for detecting an engine rotational speed of said internal combustion engine;

target load level setting means for setting a target load level according to the load correlation value detected by said load correlation value detecting means and the engine rotational speed detected by said rotational speed detecting means;

target air/fuel ratio setting means for setting a target air/fuel ratio at a first air/fuel ratio which is on a fuel-leaner side of a stoichiometric air/fuel ratio when said compression stroke injection mode is selected, and at a second air/fuel ratio which is on a fuel-richer side of said first air/fuel ratio when said intake stroke injection mode is selected;

intake amount correcting means for changing an amount of intake supplied to said internal combustion engine;

intake correction amount setting means for setting, according to the target load level set by said target load level setting means, a first intake correction amount required in said compression stroke injection mode or a second intake correction amount required in said intake stroke injection mode; and

intake amount correction control means for controlling operation of said intake amount correcting means according to said first or second intake correction amount set by said intake correction amount setting means.

2. The control unit for an in-cylinder injection internal combustion engine of claim 1, wherein said intake amount correction control means sets said first intake correction amount required for said first air/fuel ratio in said compression stroke injection mode greater than said second intake correction amount required for said second air/fuel ratio in said intake stroke injection mode.

3. The control unit for an in-cylinder injection internal combustion engine of claim 1, wherein said intake amount correction control means sets a control amount of said intake amount correcting means required in each of said injection modes according to a parameter which is in correlation with an intake opening area adjusted in accordance with a state of load of said internal combustion engine.

4. The control unit for an in-cylinder injection internal combustion engine of claim 3, wherein said intake amount correction control means sets a first control amount of said intake amount correcting means for obtaining a predetermined air amount required in said compression stroke injection mode greater than a second control amount of said intake amount correcting means for obtaining said predetermined air amount required in said intake stroke injection mode.

5. The control unit for an in-cylinder injection internal combustion engine of claim 1, further comprising: operation environmental state detecting means for detecting at least one of a shift state of a transmission coupled to said internal combustion engine, operation state of an accessory directly or indirectly driven by said internal combustion engine, and an atmospheric pressure.

6. The control unit for an in-cylinder injection internal combustion engine of claim 5, further comprising: target load level correcting means which determines a target environmental load level according to an operation environmental state detected by said operation environmental state detecting means, and determines a corrected target load level from said target environmental load level and the target load level set by said target load level setting means,

wherein said intake correction amount setting means sets, according to the corrected target load level determined by said target load level correcting means, said first or second intake correction amount required in said compression stroke injection mode or intake stroke injection mode.

7. The control unit for an in-cylinder injection internal combustion engine of claim 6, wherein said target load level correcting means computes an environmental load correction amount corresponding to each operation environmental state detected by said operation environmental state detecting means and the engine rotational speed detected by said rotational speed detecting means.

8. The control unit for an in-cylinder injection internal combustion engine of claim 5, wherein said load correlation value detecting means is constituted by throttle valve opening detecting means for detecting an opening degree of a first throttle valve disposed in an intake passage of said internal combustion engine.

9. The control unit for an in-cylinder injection internal combustion engine of claim 8, wherein said intake correction amount setting means sets, when said throttle valve opening detecting means detects a full open state of said throttle valve, a first intake correction amount corresponding to a predetermined change in an operation environmental state detected by said operation environmental state detecting means in said compression stroke injection mode greater than a second intake correction amount corresponding to said predetermined change in the operation environmental state in said intake stroke injection mode.

10. The control unit for an in-cylinder injection internal combustion engine of claim 5, further comprising: environmental intake amount correcting means which determines an environmental correction intake amount according to an operation environmental state detected by said operation environmental state detecting means, determines a third intake correction amount from said environmental correction intake amount and said first intake correction amount required in said compression stroke injection mode and set by said intake correction amount setting means, and determines a fourth intake correction amount from said environmental correction intake amount and said second intake correction amount required in said intake stroke injection mode and set by said intake correction amount setting means.

11. The control unit for an in-cylinder injection internal combustion engine of claim 10, wherein said environmental intake amount correcting means computes an environmental correction intake amount corresponding to each operation environmental state detected by said operation environmental state detecting means and the engine rotational speed detected by said rotational speed detecting means.

12. The control unit for an in-cylinder injection internal combustion engine of claim 10, wherein said intake correction amount setting means sets said first intake correction amount required for said first air/fuel ratio in said compression stroke injection mode greater than the second intake correction amount required for said second air/fuel ratio in said intake stroke injection mode.

13. The control unit for an in-cylinder injection internal combustion engine of claim 10, wherein said intake amount correction control means sets a first control amount of said intake amount correcting means for obtaining a predetermined air amount required in said compression stroke injection mode greater than a second control amount of said intake amount correcting means for obtaining said predetermined air amount required in said intake stroke injection mode.

14. The control unit for an in-cylinder injection internal combustion engine of claim 1, including an air bypass passage which bypasses a first throttle valve disposed in an intake passage of said internal combustion engine and communicates with said intake passage upstream and downstream said first throttle valve, and an electric air bypass valve for opening and closing the air bypass passage,

wherein said intake amount correction control means controls said air bypass valve such that an intake amount supplied through said air bypass passage becomes said first or second intake correction amount.

15. The control unit for an in-cylinder injection internal combustion engine of claim 14, wherein said intake amount correction control means sets a first opening control amount of said air bypass valve for obtaining a predetermined air amount required in said compression stroke injection mode greater than a second operation opening control amount of said air bypass valve for obtaining said predetermined air amount required in said intake stroke injection mode.

16. The control unit for an in-cylinder injection internal combustion engine of claim 1, wherein said load correlation value detecting means is constituted by accelerator opening detecting means for detecting an opening degree of an accelerator pedal which is attached to a vehicle installing said internal combustion engine therein and is operated by a driver,

wherein said internal combustion engine comprises:

a second throttle valve for electrically opening and closing an intake passage of said internal combustion engine,

target opening degree setting means for setting a target opening degree of said second throttle valve according to an opening degree of the accelerator pedal detected by said accelerator opening detecting means, and

throttle opening control means for controlling said second throttle valve so as to attain the target opening degree set by said target opening degree setting means;

wherein said intake amount correcting means is constituted by said second throttle valve and throttle opening control means.

17. The control unit for an in-cylinder injection internal combustion engine of claim 16, wherein said intake amount correction control means sets a first opening degree correction amount of said second throttle valve with respect to said target opening degree for obtaining a predetermined air amount required in said compression stroke injection mode greater than a second opening degree correction amount of said second throttle valve with respect to said target opening degree for obtaining said predetermined air amount required in said intake stroke injection mode.

18. The control unit for an in-cylinder injection internal combustion engine of claim 1, further comprising: intake amount detecting means for detecting an amount of intake supplied to said internal combustion engine,

wherein said target air/fuel ratio setting means determines the target air/fuel ratio according to the intake amount detected by said intake amount detecting means when said intake stroke injection mode is selected, and according to the load correlation value detected by said load correlation value detecting means when said compression stroke injection mode is selected.

19. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and is adapted to select, according to an operation state of said internal combustion engine, a compression stroke injection mode for mainly injecting fuel at a compression stroke and an intake stroke injection mode for mainly injecting fuel at an intake stroke,

said control unit comprising:

load correlation value detecting means for detecting a load correlation value of said internal combustion engine;

rotational speed detecting means for detecting an engine rotational speed of said internal combustion engine;

target load level setting means for setting a target load level according to the load correlation value detected by said load correlation value detecting means and the engine rotational speed detected by said rotational speed detecting means;

target air/fuel ratio setting means for setting a target air/fuel ratio at a first air/fuel ratio which is on a fuel-leaner side of a stoichiometric air/fuel ratio when said compression stroke injection mode is selected, and at a second air/fuel ratio which is on a fuel-richer side of said first air/fuel ratio when said intake stroke injection mode is selected;

intake amount correcting means for changing an amount of intake supplied to said internal combustion engine;

intake correction amount setting means for setting, according to the target load level set by said target load level setting means, an intake correction amount;

intake correction amount adjusting means for adjusting said intake correction amount according to a correction coefficient corresponding to a selected injection mode; and

intake amount correction control means for controlling operation of said intake amount correcting means according to the intake correction amount adjusted by said intake correction amount adjusting means corresponding to each injection mode.

20. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and which selectively takes, according to an operation state of said internal combustion engine, a compression-stroke injection mode to mainly inject fuel during a compression stroke and an intake-stroke injection mode to mainly inject fuel during an intake stroke, said control unit comprising:

load correlation value detecting means for detecting a load correlation value of the internal combustion engine;

rotational speed detecting means for detecting an engine rotational speed of the internal combustion engine;

target load level setting means for setting a target load level according to the load correlation value detected by said load correlation value detecting means and the engine rotational speed detected by said rotational speed detecting means;

target air/fuel ratio setting means for selectively setting, based on a predetermined relationship between various operation states of the internal combustion engine and their corresponding target air/fuel ratio values, the target air/fuel ratio to a first air/fuel ratio value, which fuel is leaner than a stoichiometric air/fuel ratio, when said compression-stroke injection mode is selected, and to a second air/fuel ratio value, which fuel is richer than said first air/fuel ratio value, when said intake-stroke injection mode is selected, according to at least one of said operation state and/or operation environmental state detected by an operation state detecting means;

intake amount adjusting means for changing an amount of intake fuel supplied to the internal combustion engine;

target intake amount setting means for setting, based on a predetermined relationship between various operational states of the internal combustion engine and their corresponding target intake amount values, the target intake amount to a first target intake amount value required in said compression stroke injection mode and a second target intake amount value required in said intake-stroke injection mode, according to the target load level set by said target load level setting means;

intake correction amount setting means for setting a first intake correction amount (Q2) corresponding to said first target intake amount, which is required in said compression-stroke injection mode, and a second intake correction amount (Q1) corresponding to said second target intake amount, which is required in said intake-stroke injection mode; and

intake amount control means for controlling operation of said intake amount adjusting means, selectively based on said first target intake amount, which is set by said target intake amount setting means, and said first correction amount, which is set by said intake correction amount setting means, while the internal combustion engine takes the compression-stroke injection mode, and based on said second target intake amount, which is set by said target intake amount setting means, and said second intake correction amount, which is set by said intake correction amount setting means, while the internal combustion engine takes the intake-stroke injection mode.

21. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and which selectively takes, according to an operation state of said internal combustion engine, a compression-stroke injection mode to mainly inject fuel during a compression stroke and an intake-stroke injection mode to mainly inject fuel during an intake stroke, said control unit comprising:

load correlation value detecting means for detecting a load correlation value of the internal combustion engine;

rotational speed detecting means for detecting an engine rotational speed of the internal combustion engine;

target load level setting means for setting a target load level according to the load correlation value detected by said load correlation value detecting means and the engine rotational speed detected by said rotational speed detecting means;

target air/fuel ratio setting means for selectively setting, based on a predetermined relationship between various operation states of the internal combustion engine and their corresponding target air/fuel ratio values, the target air/fuel ratio to a first air/fuel ratio value, which fuel is leaner than a stoichiometric air/fuel ratio, when said compression-stroke injection mode is selected, and to a second air/fuel ratio value, which fuel is richer than said first air/fuel ratio value, when said intake-stroke injection mode is selected, according to at least one of said operation state and/or operation environmental state detected by an operation state detecting means;

intake amount adjusting means for changing an amount of intake fuel supplied to the internal combustion engine;

target intake amount setting means for setting, based on a predetermined relationship between various operational states of the internal combustion engine and their corresponding target intake amount values, the target intake amount, according to the target load level set by said target load level setting means;

intake correction amount setting means for setting an intake correction amount corresponding to the target intake amount set by said target intake amount setting means;

intake correction amount adjusting means for adjusting the intake correction amount set by said intake correction amount setting means, based on a correction coefficient corresponding to the injection mode being selected; and

intake amount control means for controlling operation of said intake amount adjusting means based on the adjusted intake correction amount, which is adjusted by said intake correction amount adjusting means.

22. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and which selectively takes, according to an operation state of said internal combustion engine, a compression-stroke injection mode to mainly inject fuel during a compression stroke and an intake-stroke injection mode to mainly inject fuel during an intake stroke, said control unit comprising:

operation state detecting means for detecting an operation state of the internal combustion engine and/or an operation environmental state of the internal combustion engine;

intake amount adjusting means for changing an amount of intake fuel supplied to the internal combustion engine;

intake correction amount setting means for setting an intake correction amount according to the operation state and/or the operation environmental state detected by said operation state detecting means, based on a predetermined relationship between said intake correction amount and the operation state and/or the operation environmental state, said relationship being adapted to be used while the engine is running idle, and being set independently for said compression-stroke injection mode and said intake-stroke injection mode; and

intake amount control means for controlling operation of said intake amount adjusting means, based on the intake correction amount set by said intake correction amount setting means.

23. A control unit for an in-cylinder injection internal combustion engine in which fuel is directly injected into a combustion chamber and which selectively takes, according to an operation state of said internal combustion engine, a compression-stroke injection mode to mainly inject fuel during a compression stroke and an intake-stroke injection mode to mainly inject fuel during an intake stroke, said control unit comprising:

operation state detecting means for detecting an operation state of the internal combustion engine and/or an operation environmental state of the internal combustion engine;

intake amount adjusting means for changing an amount of intake fuel supplied to the internal combustion engine;

intake correction amount setting means for setting, according to a predetermined relationship between an intake correction amount and the operation state and/or the operation environmental state of the internal combustion engine, said intake correction amount in such a manner that said intake correction amount differs between in said compression-stroke injection mode and in said intake-stroke injection mode, even with the same torque generated in said both modes; and

intake amount control means for controlling operation of said intake amount adjusting means, based on the intake correction amount set by said intake correction amount setting means.