JP3398567B2 - In-cylinder direct injection internal combustion engine with variable valve timing means - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder direct injection internal combustion engine in which a liquid fuel such as gasoline is directly injected into a cylinder and burned, and more particularly, at least the valve timing of an intake valve is changed. The present invention relates to a direct injection type internal combustion engine, which is equipped with a valve timing varying means capable of performing the above.

[0002]

2. Description of the Related Art As an engine belonging to an internal combustion engine using gasoline as a fuel, an intake port internal combustion engine for injecting fuel into an intake port has been put into practical use about 20 years ago, and it is now worldwide. It has become the mainstream of gasoline engines.
A general intake port injection type internal combustion engine 1 is shown in FIG.
1 illustrates a schematic structure of one cylinder. The structure of the main body of the intake port injection type internal combustion engine 1 is also the same as that of a well-known conventional gasoline engine. The engine 1 includes a cylinder block 3 forming a cylinder 2 therein and a cylinder head attached to the cylinder block 3. 4, a cylinder head 4 is formed with an intake port 5 and an exhaust port 6, and a combustion chamber 8 is provided between the top surface of a piston 7 slidingly engaged in the cylinder 2 and the cylinder head 4. It is formed. And combustion chamber 8
An intake valve 9 is provided at the opening of the intake port 5 with respect to
An exhaust valve 10 is provided at the opening of the exhaust port 6.

The intake port injection type internal combustion engine 1, as its name implies, is capable of injecting a liquid fuel such as gasoline into the intake port 5, a so-called intake port fuel injection valve 11 (abbreviated as "port injection"). Valve 11 ”), and the opening and closing of the in-port injection valve 11 is controlled by an electronic control unit (ECU) 12. ECU1
2 is an injection timing based on a signal indicating an operating state of the engine, which is input from an air flow meter 14 provided in an intake passage 13 communicating with the intake port 5, a crank angle sensor 16 provided on a crank shaft 15 of the engine, and the like. Or injection time, that is, the injection amount is calculated, and a drive signal is output to output the injection valve 11 in the port.
Open the valve. In FIG. 4, 17 is an accelerator pedal operated by the driver, 18 is a throttle valve that opens and closes the intake passage 13 to adjust the intake amount, 19 is a fuel tank, and 20 is a fuel tank.
Is a fuel pump for pressurizing the fuel to a pressure higher than the injection pressure, and 21 is a spark plug.

In the intake port injection type internal combustion engine 1, since the injection valve 11 in the port injects fuel into the intake port 5, the injected fuel adheres to the inner wall of the intake port 5 to form the fuel oil film 22. Form. In the operating state in which the in-port injection valve 11 increases the fuel injection amount, the thickness of the fuel oil film 22 is in the range corresponding to the operating state of the engine 1,
Since a part of the fuel injected from the in-port injection valve 11 adheres to the inner wall surface of the intake port 5 until reaching the range,
Inside the cylinder 2 that actually includes the combustion chamber 8 (referred to as "in the cylinder")
The amount of fuel supplied to
The amount injected from is reduced by the amount attached to the inner wall surface of the intake port 5.

When the operating condition changes and the in-port injection valve 11 reduces the fuel injection amount, the fuel oil film 22
Since the fuel continues to evaporate from the fuel oil film 22 until the thickness corresponding to the new operating condition is reached, the amount of fuel actually supplied into the cylinder is the amount injected from the in-port injection valve 11 at that time. More than. Therefore, the intake port injection type internal combustion engine still has some problems in response to control and performance at cold start.

In order to deal with this problem, an in-cylinder direct injection internal combustion engine has been proposed in which fuel is directly injected into the cylinder of the engine, that is, into the cylinder including the combustion chamber, in place of the intake port injection internal combustion engine. ing. Japanese Unexamined Patent Publication No. 4-183945 discloses an example thereof. In the in-cylinder direct injection internal combustion engine, a fuel injection valve is attached to the cylinder head, and fuel injected from the fuel injection valve is directly supplied into the cylinder. Therefore, since the fuel injected from the fuel injection valve does not directly adhere to the inner wall surface of the intake port, the responsiveness is deteriorated due to the fuel oil film adhered to the intake port unlike the internal combustion engine of the intake port injection type. Etc. should basically not happen.

However, as is often done in the conventional intake port injection type internal combustion engine, the intake valve and the direct injection type internal combustion engine are also used for the purpose of improving engine performance such as engine output and exhaust characteristics. In order to variably control the opening timing of the exhaust valve, it is considered to provide a valve timing changing means in the drive mechanism of the intake valve and the exhaust valve. Therefore, in-cylinder equipped with such valve timing changing means In a direct-injection internal combustion engine, when a backflow of intake air from the cylinder into the intake port, that is, a blowback occurs due to operating conditions, the fuel injected into the cylinder, particularly the fuel oil film adhering to the wall of the combustion chamber or cylinder A portion of the relatively heavy fuel that forms the fuel flows back into the intake port and adheres to the inner wall surface of the intake port to form a fuel oil film that is relatively difficult to evaporate. In addition to causing similar problems to the internal combustion engine with responsiveness and poor starting performance, some of the exhaust gas remaining in the cylinder flows back into the intake port along with the intake air during blowback. Therefore, the interaction with the heavy fuel oil film causes deposits on the inner wall surface of the intake port due to the components of the exhaust gas, blocking the opening of the EGR passage to the intake port, and hindering the smooth operation of the throttle valve. May cause problems such as

Further, in the in-cylinder direct injection internal combustion engine, during the valve overlap period when the valve timing of the intake valve with respect to the exhaust valve is controlled to the advance side in this way, from the in-cylinder to the intake port. When not only relatively heavy fuel is blown back, but also when the valve timing of the intake valve is controlled toward the retard side, the piston starts rising from the bottom dead center at the end of the intake stroke and the intake valve actually closes. Even when the supercharging effect due to the inertia of the intake air flow disappears at the end of the period up to, the fuel is blown back from the cylinder to the intake port.

The problem of blowback also occurs in the conventional intake port injection type internal combustion engine 1 as shown in FIG. 4 (a). The engine 1 is also provided with a valve timing varying means as is conventionally done for the purpose of improving engine performance, and the valve timing of the intake valve 9 as shown by Ta in the upper part of FIG. Is advanced, a relatively large valve overlap period Vo is generated between the exhaust valve 10 and the exhaust valve 10, so that the exhaust valve 10 and the intake valve 9 are simultaneously opened in the exhaust stroke in which the piston 7 rises. When it occurs, the cylinder 2 containing the combustion chamber 8
Blow-back of intake air or the like occurs from the inside (inside the cylinder) to the intake port 5.

Therefore, in the conventional intake port injection type internal combustion engine equipped with the variable valve timing means,
As shown in the lower part of FIG. 4B, the valve overlap period Vo is almost zero like the valve timing Td, and the exhaust valve 10 and the intake valve 9 are simultaneously opened in the ascending stroke of the piston 2 to blow back. Under an operating condition in which fuel injection cannot occur, the fuel injection from the in-port injection valve 11 can be performed in any stroke, and the valve opening timing of the intake valve 9 is controlled to advance. Under operating conditions such as Ta where the valve overlap period Vo is long and blowback to the intake port 5 is likely to occur, fuel injection is performed substantially only in the intake stroke after top dead center. It is common to control the timing to prevent harmful blowback to the intake port.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional intake port injection type internal combustion engine and the improved direct injection type internal combustion engine. By preventing backflow of some intake air and exhaust gas from the cylinder of the engine to the intake port, and preventing fuel oil film and deposits from adhering to the inner wall surface of the intake port, there are no secondary problems. In addition, the engine control response and cold startability are higher than those of the intake port injection type internal combustion engine. By improving the combustion state, it is possible to improve fuel efficiency, reduce emissions, and increase output torque. It is an object of the present invention to provide a novel in-cylinder direct injection internal combustion engine.

[0012]

The present invention provides a cylinder direct injection internal combustion engine as set forth in each of the claims as a means for solving the above problems.

In the in-cylinder direct injection internal combustion engine according to the first aspect, the throttle valve and the throttle valve control means are respectively provided in the intake passage after branching toward each cylinder, and the valve overlap period is provided. Since the throttle valve control means controls the opening degree of each throttle valve to the valve closing side, the blowback from the cylinder to the intake port, which is likely to occur during the valve overlap period, is reliably prevented for each cylinder. Prevents fuel oil film and deposits from adhering to the inner wall surface of the. As a result, higher performance can be obtained in control response and cold startability of the engine than in the conventional intake port internal combustion engine. Further, the combustion state is improved, and it is possible to improve fuel efficiency, reduce emissions, and increase output torque.

In this case, the throttle valve control means is light,
The opening of each throttle valve is controlled to the closing side during the valve overlap period at medium load, but at high load, the throttle valve opening is closed only when the valve overlap period is long. However, when the valve overlap period is short, blowback is unlikely to occur, so the valve may not be controlled to close.

The throttle valve control means in the direct injection type internal combustion engine according to the third aspect of the invention causes blowback during the period from the bottom dead center at the end of the intake stroke to the intake valve closing at light and medium loads. At that time, the opening of the throttle valve is controlled to the closing side to prevent blowback, but blowback does not easily occur during the same period by aiming at inertial intake at high load, so the throttle valve should be opened during that period. Keep it fully open. This surely prevents blowback from the inside of the cylinder to the intake port for each cylinder,
Higher performance is obtained in control response and cold startability of the engine than in the conventional intake port internal combustion engine. Also,
It is possible to improve the combustion state, improve fuel efficiency, reduce emissions, and increase output torque.

The throttle valve control means in the direct injection type internal combustion engine of the present invention has a condition in which blowback is likely to occur, that is, in a high load operation state, when the valve overlap period is large, and in a light and medium load operation state. The throttle valve opening of each cylinder is controlled to the closing side during the entire valve overlap period and from the bottom dead center to the closing of the intake valve, so blowback is reliably prevented in any operating state. can do. The valve timing varying means in the direct injection type internal combustion engine of the present invention is designed to reduce the fuel consumption and emissions at light and medium loads, and to increase the output torque at high loads, at least the valve timing of the intake valve. It is desirable to set to control to the optimum value. In addition to the above, the throttle valve control means in the in-cylinder direct injection internal combustion engine of the present invention determines the period in which the blowback from the cylinder to the intake port increases for each cylinder, and is provided for each cylinder only for that period. The throttle valve openings can be set so as to be controlled to the valve closing side.

The cylinder direct injection type internal combustion engine according to claim 7 is provided with the throttle valve control means for controlling the opening degree of the throttle valve of each cylinder to the closing side at the beginning of the intake stroke. By fully closing the throttle valve of each cylinder at the beginning of the intake stroke, a negative pressure is generated in the cylinder, and the fuel injected by this is vaporized and atomized,
Since the fuel oil film formed on the wall surface in the cylinder is also vaporized and reduced, a homogeneous air-fuel mixture is formed in the cylinder, the combustion state is improved, the fuel efficiency is improved, and the emission is also reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a first embodiment of the present invention. (A) is an in-cylinder direct injection internal combustion engine 31 (this is abbreviated as "in-cylinder direct injection engine 31").
FIG. 4 is a cross-sectional view illustrating the schematic structure of one cylinder of FIG. 4, which should be compared with FIG. 4A showing an example of a conventional intake port internal combustion engine 1. (B) is a conceptual plan view of the entire cylinder direct injection engine 31. The in-cylinder direct injection engine 31 shown in FIG. 1 has the same basic configuration as the internal combustion engine as that of the conventional engine 1. Therefore, in FIG. The overlapping description is omitted by adding. That is, 2 is a cylinder, 3 is a cylinder block, 4 is a cylinder head,
5 is an intake port, 6 is an exhaust port, 7 is a piston, 8 is a combustion chamber, 9 is an intake valve, 10 is an exhaust valve, 12 is an electronic control unit (ECU), 13 is an intake passage, 14 is an air flow meter, 15 Is a crankshaft, 16 is a crank angle sensor, 1
7 is an accelerator pedal, 18 is a throttle valve, 19 is a fuel tank, 20 is a fuel pump, and 21 is a spark plug.

In addition to the above, in FIG. 1, numeral 23 is a throttle position sensor for detecting the opening degree of the throttle valve 18, and numeral 24 is a valve timing for opening and closing the intake valve 9 and the exhaust valve 10. A possible valve timing varying means (hereinafter abbreviated as "VVT 24") is shown.

The in-cylinder direct injection engine 31 shown in FIG. 1 does not have an in-port injection valve in the intake port 5 but directly injects fuel into the cylinder 2 (in the cylinder) including the combustion chamber 8. The in-cylinder direct fuel injection valve 32 (which will be abbreviated as "in-cylinder direct injection valve 32") is provided. In addition to the throttle valve 18 provided in the common intake passage 13, the intake port 5 from each intake passage 13
As shown in FIG. 1 (b), an independent throttle valve 33 is provided for each cylinder in the intake passage after branching toward each side, and in the illustrated case, the intake port 5 itself. The throttle valve 33 is controlled to be opened and closed independently for each cylinder by the throttle valve control means. The throttle valve control means is an operating means provided for each cylinder, that is, a hydraulic actuator 34 in the illustrated example, a solenoid valve 35 for operating the hydraulic actuator 34, and an electronic control device common to each cylinder for controlling the solenoid valve 35. (ECU) 12.

In the direct injection type internal combustion engine 31 of the present invention, for the purpose of improving the performance of the engine, the timing of opening and closing the intake valve 9 and the exhaust valve 10 is controlled by the valve timing varying means (VVT) 24. You can change it freely. In the case of the embodiment shown in FIG.
Although the VT 24 is controlled by the ECU 12, it may be configured to be controlled by other means. In order to determine the operating state of the in-cylinder direct injection engine 31, the ECU 12 is provided with a throttle valve opening Tha indicating the magnitude of the load from the crank angle sensor 16 and the engine speed Ne and the crank angle Ca, and the throttle position sensor 23. Signal is input.

In the operating state of the in-cylinder direct injection engine 31, the ECU 12 operates the VVT 24 so that the fuel consumption and emission are reduced at light and medium loads, and the output torque is increased at high load. The valve timing of the intake valve 9 (and the exhaust valve 10) is controlled to an optimum value. Then, in the in-cylinder direct injection engine 31 of this embodiment, the ECU 12 determines, for each cylinder, a period in which a large amount of air is blown back from the cylinder 2 into the intake port 5, such as the valve overlap period Vo. The characteristic feature is that the throttle valve 33 provided for each cylinder is independently closed for that period of time to operate so as to block the blowback.

As a specific control method for obtaining such an operation, an example of a control map set in a ROM (not shown) in the ECU 12 is shown in FIG. 2 (a). In the operating state of the in-cylinder direct injection engine 31, the opening degree Tha of the throttle valve 18
According to the operating conditions specified as points on the chart of FIG. 2 (a) from the engine speed Ne of the engine 31 and fuel consumption and emissions can be reduced at light and medium loads, and at high loads. The optimum valve overlap amount Vos that can increase the output torque is preset as a region on this chart.

As shown by the hatched area in the diagram of FIG. 2 (a), the range of operating conditions where the blowback is large is as follows:
A low rotation speed and a small opening of the throttle valve 18,
In the medium load region Bf, in the diagram showing the valve timing and the fuel injection timing of FIG. 2B, the fuel injection timing (intake stroke injection Fis and compression stroke injection Fic in the cylinder direct injection engine 31 is shown. ) Is after the top dead center at which the intake stroke starts, the fuel injected from the in-cylinder direct injection valve 32 into the cylinder 2 is not directly blown back to the intake port 5, but as described above, The blowback of heavy fuel adhering to the inner wall surface of the cylinder 2 including the chamber 8 becomes a problem.

Therefore, in this embodiment, the ECU 12
However, based on the signal from the throttle position sensor 23 (throttle valve opening Tha) and the signal from the crank angle sensor 16 (engine speed Ne, crank angle Ca), the operating state of the target cylinder at that time is Area B that increases
ECU 12 immediately operates the solenoid valve 35 during the valve overlap period Vo to determine whether the independent throttle valve 3 provided in the target cylinder is operated.
By fully closing 3 by the hydraulic actuator 34, it is possible to prevent the heavy fuel attached to the inner wall surface of the cylinder 2 including the combustion chamber 8 of the cylinder from blowing back to the intake port 5.

During this period, since both the intake valve 9 and the exhaust valve 10 are open, even if the intake port 5 side is closed by the independent throttle valve 33, there is no fear that fuel consumption will deteriorate due to an increase in pumping loss. . Also, when the load is high, the difference between the intake pressure and the exhaust pressure becomes small, so
Since the blowback is less than that under a medium load, the independent throttle valve 33 is fully closed as described above only when the valve overlap period Vo is large. Alternatively, a condition may be set in which the independent throttle valve 33 is not closed.

Next, from the bottom dead center at the end of the intake stroke, the intake valve 9
A method for suppressing blowback in the period Is until the valve is closed will be described with reference to FIG. During this period, as shown in the upper part of FIG. 3, in order to increase the output torque in the high load operation state, inertia intake (supercharging) is performed before the closing timing of the intake valve 9. Since the period is provided, the valve timing is controlled centering on the closing timing of the intake valve 9 in the high load operation state, so that the intake air is not blown back during this period Is during high load.

However, in the light and medium load operating states, as shown in the middle part of FIG. 3, the valve timing is set to the valve timing in order to reduce emissions and improve fuel efficiency by performing internal EGR within the valve overlap period Vo. When the amount of overlap is set as the center, the flow velocity of the intake flow becomes low and the inertia becomes weak at light and medium loads, so the fuel injected in the intake stroke (intake stroke injection F
is), the heavy fuel attached to the inner wall surface of the cylinder 2 including the combustion chamber 8 is blown back to the intake port 5 in the period Is from the bottom dead center to the intake valve closing.

Therefore, at the time of high load, the independent throttle valve 33 is fully opened during the period from the bottom dead center to the intake valve closing, that is, the period Is for inertial intake, to sufficiently perform inertia supercharging. During the medium load, the independent throttle valve 33 is fully closed during the period Is from the bottom dead center to the intake valve closing to prevent the blowback. At this time, the torque for compressing the intake air increases, which may cause deterioration of fuel efficiency. However, the compression end temperature rises and the fuel spray floating in the cylinder including the combustion chamber 8 is increased. Since the atomization (vaporization) of (1) advances and the combustion is improved, the fuel efficiency as a whole does not deteriorate.

Thus, in the high load operation state, only when the valve overlap period Vo is large,
In the light and medium load operation state, the entire valve overlap period Vo and the period Is from the bottom dead center to the closing of the intake valve 9 Is
In the above, by fully closing the independent throttle valve 33 provided in the intake port 5 of the target cylinder, the injected fuel and the heavy fuel adhering to the inner wall surface of the cylinder 2 including the combustion chamber 8 are exhausted. At the same time, it is possible to reliably prevent the air from being blown back into the intake port 5.

The method of suppressing blowback by controlling the independent throttle valve 33 of each cylinder by the ECU 12 has been described above.
3 makes it possible to improve the performance of the engine.
An example thereof will be described as a second embodiment of the present invention. Generally, in the direct injection type internal combustion engine, the fuel injection timing is limited as compared with the internal combustion engine of the intake port injection type. Therefore, since the time from injection to ignition is short, it is difficult to completely atomize the fuel, and since the fuel is directly injected into the cylinder, a heavy fuel oil film is formed on the inner wall surface of the cylinder 2 including the combustion chamber. It is generally said that it is difficult to form a homogeneous air-fuel mixture in a direct injection type internal combustion engine, which is a direct injection type internal combustion engine, as compared with an internal combustion engine of the intake port injection type.

Therefore, in the second embodiment, FIG.
In the in-cylinder direct injection engine 31 similar to the first embodiment shown in (a) and (b), as shown in FIG. 5, the independent throttle valve 33 is fully closed in the initial period Vcs of the intake stroke. As a result, a negative pressure is generated in the cylinder, and the injection period F
It promotes vaporization of the fuel injected at is and the fuel oil film adhering to the wall surface in the cylinder, and forms a homogeneous air-fuel mixture. EC
Due to such control of the independent throttle valve 33 by U12, even if the pumping loss is slightly increased, the fuel is atomized further and the homogeneous fuel-air mixture is formed due to the reduction of the fuel oil film adhering to the wall surface in the cylinder. The effect of improving the combustion state, that is, the effect of improving fuel efficiency and reducing emissions can be obtained.

In each of the above-described embodiments, as the throttle valve control means provided for opening / closing the independent throttle valve 33, the ECU 12, the solenoid valve 35 controlled by the ECU 12, and the operating means including the hydraulic actuator 34 are provided. Although illustrated, the operating means for the independent throttle valve 33 is not limited to this, and it is needless to say that a general actuator such as one using air pressure or an electric motor can be used for this purpose. Yes.
Further, the independent throttle valves 33 of each cylinder do not necessarily have to be controlled independently, and if there are different throttle valves 33 of different cylinders such as 90-degree phase, combine them appropriately. Thereby, it is also possible to drive in different phases by means of a common actuating means, which makes it possible to reduce the number of actuating means.

[Brief description of drawings]

FIG. 1 illustrates a configuration of a cylinder direct injection internal combustion engine as a first embodiment of the present invention, in which (a) is a vertical sectional front view of one cylinder, and (b) is an overall plan view. is there.

2A and 2B are diagrams for explaining a control method in the first embodiment, where FIG. 2A is an example of a control map set in the ECU, and FIG. 2B is a line showing valve timing and fuel injection timing. It is a figure.

FIG. 3 is a diagram showing a valve timing and a valve closing timing of a throttle valve independent of each cylinder for each operating state in order to specifically show a control method in the first embodiment.

FIG. 4 illustrates a configuration of an internal combustion engine with an intake port injection as a conventional technique, in which (a) is a vertical sectional front view of one cylinder, and (b) is a diagram showing valve timing and fuel injection timing. Is.

FIG. 5 is a diagram showing, as a second embodiment of the present invention, a method of controlling an independent throttle valve different from the above-mentioned control method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Injection port internal combustion engine (conventional technology) 2 ... Cylinder 5 ... Intake port 7 ... Piston 8 ... Combustion chamber 9 ... Intake valve 10 ... Exhaust valve 11 ... Intake port fuel injection valve (prior art) 12 ... Electron Control unit (ECU) 16 ... Crank angle sensor 18 ... Throttle valve 22 ... Fuel oil film (conventional technology) 23 ... Throttle position sensor 24 ... Valve timing variable means (VVT) 31 ... In-cylinder direct injection internal combustion engine (direct in-cylinder) Injection engine) 32 ... In-cylinder direct fuel injection valve (in-cylinder direct injection valve) 33 ... Independent throttle valve for each cylinder 34 ... Hydraulic actuator 35 ... Electromagnetic valve Bf ... Region where much blowback occurs Fic ... Compression stroke injection Fis ... Intake stroke injection Is ... period from bottom dead center to intake valve closing (period for inertial intake) Tb ... base timing Vcs ... initial period Vo of intake stroke Vo ... valve overlap Up period Vos ... Optimal valve overlap amount

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 13/02 F02D 13/02 J (72) Inventor Kimitaka Saito 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Co., Ltd. In-house (72) Inventor Tatsuo Kobayashi 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (56) Reference JP 4-86326 (JP, A) JP 5-222940 (JP, A) Special Kaihei 9-317520 (JP, A) JP-A-3-185217 (JP, A) JP-A-4-183945 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 13 / 00 F02D 41/00-45/00 395

Claims (7)

(57) [Claims] 1. An in-cylinder direct fuel injection valve capable of directly injecting fuel into a cylinder of each cylinder, and a valve timing capable of changing at least the valve timing of an intake valve among an intake valve and an exhaust valve. In a cylinder direct injection internal combustion engine equipped with a variable means, the throttle valve provided in each intake passage after branching toward each cylinder and the opening timing of the intake valve and the exhaust valve overlap. An in-cylinder direct injection internal combustion engine provided with valve timing varying means, comprising throttle valve control means for controlling the opening degree of each of the throttle valves to a valve closing side during a valve overlap period. 2. A throttle valve control means for controlling the opening degree of the throttle valve to the valve closing side within the valve overlap period only when the valve overlap period is large under high load. An in-cylinder direct injection internal combustion engine having the valve timing varying means according to claim 1. 3. An in-cylinder direct fuel injection valve capable of directly injecting fuel into the cylinder of each cylinder, and a valve timing capable of changing at least the valve timing of the intake valve among the intake valve and the exhaust valve. In a direct-injection internal combustion engine equipped with a variable means, a throttle valve provided in each intake passage after branching toward each cylinder, and intake from a bottom dead center at the end of the intake stroke at high load Throttle valve control means is provided for keeping the throttle valves fully open during the period until the valves are closed and for controlling the opening of the throttle valves to the closing side during the periods during light and medium loads. An in-cylinder direct injection internal combustion engine equipped with valve timing varying means. 4. The valve overlap period is large in a high load operation state, and the entire valve overlap period in a light and medium load operation state, and from the bottom dead center to the closing of the intake valve. The in-cylinder direct injection internal combustion engine with valve timing varying means according to claim 3, further comprising throttle valve control means for controlling the opening degree of each of the throttle valves to a closing side during the period. organ. 5. A valve timing varying means is operated so that fuel consumption and emissions are reduced at light and medium loads, and output torque is increased at high loads, and at least the valve timing of the intake valve is set to an optimum value. The in-cylinder direct injection internal combustion engine according to any one of claims 1 to 4, further comprising valve timing varying means for controlling the valve timing. 6. The opening of the throttle valve provided for each cylinder is closed for each cylinder by determining a period during which the blowback from the cylinder to the intake port is substantially increased for each cylinder. A cylinder direct injection internal combustion engine equipped with a valve timing varying means according to any one of claims 1 to 5, further comprising a throttle valve control means for controlling the side. 7. An in-cylinder direct fuel injection valve capable of directly injecting fuel into the cylinder of each cylinder, and a valve timing capable of changing at least the valve timing of the intake valve among the intake valve and the exhaust valve. In a direct injection internal combustion engine having a variable means, a throttle valve provided in each intake passage after branching toward each of the cylinders, and an opening of the throttle valve at the beginning of the intake stroke. An in-cylinder direct injection internal combustion engine provided with valve timing varying means, characterized by comprising throttle valve control means for controlling on the valve closing side.