JP3823612B2 - Direct-injection spark ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
In a conventional direct-injection spark-ignition internal combustion engine, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-19046, an ignition plug that faces the combustion chamber from substantially the center of the cylinder head combustion chamber wall surface, and a cylinder head combustion chamber wall surface A fuel injection valve that faces the combustion chamber from the side of the intake valve side, and injects fuel from the fuel injection valve in the compression stroke to improve fuel efficiency under low, medium speed and low load conditions. Stratified combustion is performed by the mixing ratio.
[0003]
Here, by setting the intake port, stratified combustion is generated by generating a forward tumble flow (tumble flow in the direction from the fuel injection valve directly to the ignition plug) as a tumble flow of intake air (longitudinal swirl flow) in the combustion chamber. During the stratified operation in which the fuel is discharged, the fuel is reliably transported to the vicinity of the spark plug while preventing the fuel from diffusing, and the fuel can be stratified.
[0004]
However, in such a direct-injection spark-ignition internal combustion engine, when the engine is operated at a low speed and a low load condition such as in an idling range, it is easy to cause a combustion failure and, moreover, to deteriorate the operability of the engine. There was a problem.
[0005]
This is because the rotational speed of the intake air is weakened because the engine speed is low, and the tumble flow is attenuated and collapsed during the compression stroke. For this reason, the air-fuel mixture is not stratified, and combustion tends to become unstable.
[0006]
In order to deal with such problems, for example, Japanese Patent Application Laid-Open No. 7-19054 discloses a fuel spray configuration in which a convex portion adjacent to the fuel spray is provided on the cylinder head combustion chamber wall surface between the fuel injection valve and the spark plug. A fuel stratification has been disclosed in the vicinity of the ignition gap by utilizing the so-called Coanda effect that changes the pressure.
[0007]
Here, the Coanda effect refers to a tendency that a jet of gas or liquid tends to flow near the direction along the curved surface of the wall, even if the direction of the jet axis is separated from the direction of the curved wall.
[0008]
[Problems to be solved by the invention]
However, in order to use the Coanda effect, the convex portion of the wall surface and the spray outer shape need to be close to each other.
[0009]
Therefore, if the convex shape of the wall surface is determined according to the low rotation range during stratification operation where the Coanda effect is to be used, homogeneous combustion is performed by injecting fuel in the high rotation range during stratification operation or in the intake stroke. During operation, the fuel spray and the convex portion interfere with each other, resulting in an increase in unburned fuel (HC) and a deterioration in fuel consumption.
[0010]
That is, there is a problem that the combustion stability at the time of low rotation stratification operation and the reduction of unburned components at the time of high rotation stratification operation or homogeneous operation are not compatible.
In view of such conventional problems, an object of the present invention is to achieve both combustion stability during low rotation stratification operation and reduction of unburned fuel during high rotation stratification operation and homogeneous operation.
[0011]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, the spark plug that faces the combustion chamber from the approximate center of the cylinder head combustion chamber wall surface, and the fuel that faces the combustion chamber from the side of the cylinder head combustion chamber wall surface on the intake valve side. A direct injection spark ignition internal combustion engine for injecting fuel from a fuel injection valve in a compression stroke under at least a predetermined operating condition to cause stratified combustion, and a fuel injection valve and an ignition plug A fuel pressure (fuel pressure) at the time of fuel injection is provided so as to provide a convex portion adjacent to the fuel spray on the cylinder head combustion chamber wall between and the fuel spray form by the convex portion according to engine operating conditions. Alternatively, control means for controlling at least one of the in-cylinder pressure (back pressure) is provided.
[0012]
When the fuel pressure at the time of fuel injection is lowered, the spray particles become coarse, the flow velocity of the surrounding air decreases, and the Coanda effect cannot be obtained. Further, when the in-cylinder pressure at the time of fuel injection is increased, the spray external angle becomes narrower, the distance from the convex portion of the wall surface of the combustion chamber increases, and the Coanda effect cannot be obtained. Therefore, by controlling these, the use / non-use of the Coanda effect is controlled according to the engine operating conditions.
[0013]
The invention according to claim 2 is characterized in that, during the stratified operation in which stratified combustion is performed, the control means sets a high fuel pressure at a low speed and a low fuel pressure at a high speed according to the engine speed. To do.
[0014]
In the invention according to claim 3, the control means sets the low in-cylinder pressure at the time of low rotation and the high in-cylinder pressure at the time of high rotation according to the engine speed during the stratified operation in which stratified combustion is performed. Features.
[0015]
The invention according to claim 4 is characterized in that the control means sets a low fuel pressure during a homogeneous operation in which fuel is injected from a fuel injection valve in an intake stroke to perform homogeneous combustion.
[0016]
In the invention according to claim 5, in the homogeneous operation, the control means increases the fuel pressure in a region where the fuel injection amount is insufficient due to the low fuel pressure, and injects the fuel during the intake valve opening period. It is characterized by.
[0017]
The invention according to claim 6 is characterized in that the control means sets a high in-cylinder pressure during a homogeneous operation in which fuel is injected from a fuel injection valve in an intake stroke to perform homogeneous combustion.
[0018]
【The invention's effect】
According to the first aspect of the present invention, the fuel pressure (fuel pressure) or the in-cylinder pressure (back pressure) at the time of fuel injection is changed so as to change the magnitude of the Coanda effect by the convex portion of the combustion chamber wall surface according to the engine operating conditions. The use / non-use of the Coanda effect can be controlled by controlling at least one of the pressure (pressure), thereby improving the combustion stability by using the Coanda effect under a weak gas flow condition, and coanda under a strong gas flow condition. It is possible to reduce the unburned fuel content by not using the effect.
[0019]
According to the invention of claim 2, during the stratification operation, the Coanda effect is utilized during the low rotation stratification operation by setting the high fuel pressure at the low rotation and the low fuel pressure at the high rotation according to the engine speed. Thus, the combustion stability can be improved, and the unburned portion can be reduced without using the Coanda effect during the high rotation stratification operation.
[0020]
According to the third aspect of the present invention, during the stratified operation, the Coanda effect is achieved during the low rotation stratified operation by setting the low in-cylinder pressure during the low rotation and the high in-cylinder pressure during the high rotation according to the engine speed. Combustion stability can be improved by using, and unburned components can be reduced by not using the Coanda effect during high rotation stratification operation.
[0021]
According to the invention which concerns on Claim 4, by making low fuel pressure at the time of a homogeneous operation, a Coanda effect can be avoided and unburned part reduction can be aimed at.
According to the fifth aspect of the present invention, in the region where the fuel injection amount is insufficient due to the low fuel pressure during homogeneous operation, the fuel pressure is increased to eliminate the output decrease due to the fuel shortage, while the intake valve is opened. By injecting the fuel during the period, the intake valve protruding into the combustion chamber prevents the Coanda effect and can reduce the unburned amount.
[0022]
According to the invention which concerns on Claim 6, by making it the high in-cylinder pressure at the time of a homogeneous operation, unburned part reduction can be aimed at without using the Coanda effect. In this case, since the fuel pressure can be increased, the output is not reduced due to fuel shortage.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of a direct injection spark ignition internal combustion engine showing an embodiment of the present invention, and FIG. 2 is a schematic plan view of the same internal combustion engine.
[0024]
A combustion chamber 4 is formed by the cylinder head 1, the cylinder block 2 and the piston 3.
The cylinder head 1 is provided with two intake valves 6 and two exhaust valves 7 facing each other so as to surround a spark plug 5 that faces the inside of the combustion chamber 4 from the center of the wall surface of the cylinder head combustion chamber. 8 is an intake port and 9 is an exhaust port.
[0025]
The cylinder head 1 is also provided with a fuel injection valve 10 facing the combustion chamber 4 from the side of the cylinder head combustion chamber wall on the intake valve 6 side (between the two intake valves 6 and 6 and below). The fuel is injected obliquely downward into the combustion chamber 4 directly from the fuel injection valve 10.
[0026]
Here, by setting the intake port 8, the air sucked from the intake valve 6 is directed toward the exhaust valve 7, whereby the exhaust valve 7 is converted into the combustion chamber 4 as a tumble flow (vertical swirl flow). A forward tumble flow (that is, a tumble flow in the direction from the vicinity of the fuel injection valve 10 directly to the vicinity of the spark plug 5) is generated that flows downward on the side and flows upward on the intake valve 6 side. A recess (slope groove) 11 for promoting the tumble flow is formed on the crown surface of the piston 3.
[0027]
The cylinder head 1 is also adjacent to the upper portion of the fuel spray from the fuel injection valve 10 between the fuel injection valve 10 and the spark plug 5 and on the cylinder head combustion chamber wall between the two intake valves 6 and 6. Thus, the convex part 12 which has a curved surface is provided.
[0028]
The control unit 13 is input with the engine speed detected by the crank angle sensor 14, the accelerator opening (engine load) detected by the accelerator opening sensor 15, the water temperature detected by the water temperature sensor 16, and the like.
[0029]
The control unit 13 then controls the fuel injection timing of the fuel injection valve 10, the fuel injection amount, and the fuel pressure to the fuel injection valve 10 that is regulated by the pressure regulator 17 (hereinafter referred to as fuel pressure) according to the engine operating conditions detected by these. ), Controlling the ignition timing of the spark plug 5 and the opening degree of the electric throttle valve 18. In particular, under a predetermined operating condition (stratified region), the fuel injection timing of the fuel injection valve 10 is set to the compression stroke to cause stratified combustion, and under other operating conditions (homogeneous region), the fuel injector The fuel injection timing of 10 is set to the intake stroke, and homogeneous combustion is performed.
[0030]
Next, control using the convex portion 12 will be described.
The convex portion 12 is for generating the Coanda effect, and a conceptual diagram of the Coanda effect is shown in FIG.
[0031]
The fuel injected from the fuel injection valve 10 advances while entraining surrounding air as it advances. Thus, a form of air flow along the spray is formed. Here, if a combustion chamber wall is formed on the air flow side, an air flow is formed along the wall. The spray is deflected in such a manner that the spray is drawn to the formed flow.
[0032]
Therefore, by providing the convex portion 12 adjacent to the fuel spray on the cylinder head combustion chamber wall surface between the fuel injection valve 10 and the spark plug 5, the tumble flow is generated in the compression stroke in the low rotation stratification region where the gas flow is weak. Even if it decays or collapses, the fuel spray can be transported to the vicinity of the spark plug 5 by the Coanda effect.
[0033]
However, if the above-mentioned Coanda effect is desired in the low rotation stratification region where the gas flow is weak, the gas flow becomes strong in the high rotation stratification region, so that in the homogeneous region, the spray spreads due to the homogenization of the spray, Due to the spray interference on the convex portion 12, there is a concern about an increase in unburned fuel (HC) and a deterioration in fuel consumption.
[0034]
On the other hand, the Coanda effect has almost no effect when the fuel pressure is lowered as shown in FIG. This is because as the fuel pressure decreases, the spray particles become coarse, the flow velocity of the surrounding air decreases, and the Coanda effect cannot be obtained.
[0035]
Therefore, in the first embodiment, as shown in the conceptual diagram of the fuel pressure control in FIG. 4, in the low rotation stratification region including the idle, the high rotation stratification region in which the gas flow is sufficiently obtained using the Coanda effect as the high fuel pressure. In the homogeneous region, a low stratification region is obtained as a low fuel pressure, and unburned fuel is suppressed.
[0036]
FIG. 4 is a flowchart of fuel pressure control in the first embodiment, and corresponds to fuel pressure control means.
In step 101, the engine speed indicating the engine operating conditions, the engine load (accelerator opening), the water temperature, etc. are read.
[0037]
In step 102, it is determined whether the region is a stratified region or a homogeneous region based on the read engine operating conditions.
In the case of the homogeneous region, the process proceeds to step 104 where low fuel pressure control is performed by the pressure regulator 17. That is, the fuel pressure is controlled so as not to cause the Coanda effect.
[0038]
In the case of the stratified region, the process proceeds to step 103, and it is determined whether the region using the Coanda effect (mainly the low rotation region) or not using the region (high rotation region) according to the engine speed and load.
[0039]
In the case of the region using the Coanda effect (mainly in the low rotation region), the routine proceeds to step 105 where high pressure control is performed by the pressure regulator 17. That is, the fuel pressure is increased to such an extent that the Coanda effect is produced.
[0040]
In the case where the Coanda effect is not used (high rotation region), the process proceeds to step 104 described above, and the fuel pressure is controlled to a low level that does not cause the Coanda effect.
[0041]
FIG. 6 shows a spray form when the Coanda effect is used / not used.
In the region using the Coanda effect (low rotation region), as shown in FIG. 6A, the high fuel pressure fuel spray from the fuel injection valve 10 is deflected to the spark plug 5 side by the Coanda effect by the convex portion 12. Even if the gas flow is weak, it reaches the spark plug 5.
[0042]
In the region where the Coanda effect is not used (high rotation region), as shown in FIG. 6B, the Coanda effect does not occur in the low fuel pressure fuel spray from the fuel injection valve 10, but reaches the spark plug 5 by gas flow. It becomes like this.
[0043]
Next, a second embodiment of the present invention will be described.
FIG. 7 is a conceptual diagram of fuel pressure control of the second embodiment.
In the second embodiment, the fuel pressure is controlled more finely, and in particular, in the stratification region, the fuel pressure is finely controlled according to the engine speed.
[0044]
FIG. 8 is a flowchart of fuel pressure control in the second embodiment, which corresponds to fuel pressure control means.
In step 101, the engine speed indicating the engine operating conditions, the engine load (accelerator opening), the water temperature, etc. are read.
[0045]
In step 102, it is determined whether the region is a stratified region or a homogeneous region based on the read engine operating conditions.
In the case of the homogeneous region, the process proceeds to step 106, the fuel pressure map for the homogeneous region is referred to, the fuel pressure is set according to the engine speed and the load, and the fuel pressure is controlled by the pressure regulator 17 in step 107. . In this case, the fuel pressure is controlled so as not to cause the Coanda effect.
[0046]
In the case of the stratified region, the process proceeds to step 108, the fuel pressure map for the stratified region is referred to, and the fuel pressure is set so that the high fuel pressure is mainly set on the low rotation side according to the engine speed and the load. Thus, the fuel pressure is controlled by the pressure regulator 17. In this case, the fuel pressure is increased to such an extent that the Coanda effect is generated on the low rotation side, and the fuel pressure is controlled to a low level that does not cause the Coanda effect on the high rotation side.
[0047]
As an effect, it is possible to finely set the magnitude of the Coanda effect according to the engine operating conditions, and it is possible to optimize the compatibility between engine stability and unburned fuel.
[0048]
Next, a third embodiment of the present invention will be described.
FIG. 9 is a conceptual diagram of the Coanda effect as in FIG. 3, and here, particularly the influence of the Coanda effect due to the in-cylinder pressure (hereinafter referred to as back pressure) during fuel injection is shown. Especially in the case of a holo-cone (hollow cone) spray, the spray external angle becomes narrower by increasing the back pressure. Therefore, even if the convex portion 12 is provided on the wall surface of the combustion chamber and the Coanda effect is obtained under a predetermined back pressure, the Coanda effect cannot be obtained by increasing the back pressure. Since the Coanda effect depends on the flow velocity along the curved wall surface, the spray external angle becomes narrower as the back pressure rises, and when the spray is separated by increasing the distance from the convex portion 12 of the combustion chamber wall surface, the effect cannot be obtained. Because.
[0049]
Therefore, in the third embodiment, as shown in the conceptual diagram of the fuel pressure / back pressure control in FIG. 10, in the low rotation stratification region including the idle, the Coanda effect is used as the high fuel pressure / low back pressure, and the gas flow is controlled. In the high rotation stratification region that can be obtained sufficiently, high fuel pressure and high back pressure are obtained by eliminating the Coanda effect, so that a wide stratification region is obtained, and in the homogeneous region, fuel is unburned as low fuel pressure and low back pressure. To reduce the minutes.
[0050]
FIG. 11 is a flowchart of fuel pressure / back pressure control in the third embodiment, which corresponds to fuel pressure and back pressure control means.
In step 101, the engine speed indicating the engine operating conditions, the engine load (accelerator opening), the water temperature, etc. are read.
[0051]
In step 102, it is determined whether the region is a stratified region or a homogeneous region based on the read engine operating conditions.
In the case of the homogeneous region, the process proceeds to step 111, the fuel pressure map for the homogeneous region is referred to, the fuel pressure is set to a relatively low fuel pressure according to the engine speed and load, and in step 112, the pressure regulator 17 Control the fuel pressure. In this case, the fuel pressure is controlled so as not to cause the Coanda effect.
[0052]
In the case of the stratified region, the process proceeds to step 113, the fuel pressure map for the stratified region is referred to, the fuel pressure is set to a relatively high fuel pressure according to the engine speed and the load, and in step 114, the pressure regulator 17 Control the fuel pressure. In this case, the fuel pressure is increased to such an extent that the Coanda effect is produced under a low back pressure.
[0053]
In the case of the stratified region, the routine further proceeds to step 115, where it is determined whether the region using the Coanda effect (mainly the low rotation region) or not using the region (high rotation region) according to the engine speed and load.
[0054]
In the case of the region using the Coanda effect (mainly the low rotation region), the routine proceeds to step 116 where the opening degree of the electric throttle valve 18 is corrected to the closed side and set to a low back pressure. That is, the back pressure is reduced to such an extent that the Coanda effect is produced.
[0055]
Although not included in the flow, in the case where the Coanda effect is used (mainly in the low rotation range), the fuel injection timing is advanced to the extent that stability is obtained, that is, the injection start timing is You may make it move to a bottom dead center side, and you may make it inject at the compression stroke initial stage. This is because the back pressure during fuel injection is lower in the early stage of the compression stroke.
[0056]
In the case where the Coanda effect is not used (high rotation range), the process proceeds to step 117, the opening degree of the electric throttle valve 18 is corrected to the open side, and the high back pressure is set. That is, the back pressure is controlled so as not to cause the Coanda effect.
[0057]
As a result, in the low rotation stratification region including idle, a stable region is secured by the Coanda effect, and even under other operating conditions, an increase in unburned fuel (HC) due to the interference between the spray and the convex portion 12 and a deterioration in fuel consumption. Can be suppressed. In particular, by adding back pressure control, it is possible to suppress unburned content in a wider range.
[0058]
When the back pressure is increased, the amount of intake air increases, and when the target air-fuel ratio is constant, the amount of fuel is increased and the torque increases. Therefore, a torque step is generated as compared with the case of low back pressure. However, there is a torque step even when switching between the stratified operation and the homogeneous operation, and since this is adjusted by the accelerator operation, there is no particular problem.
[0059]
Next, a fourth embodiment of the present invention will be described.
FIG. 12 is a conceptual diagram of fuel pressure / back pressure control according to the fourth embodiment.
In the fourth embodiment, the fuel injection amount is insufficient in the homogeneous region because there is a possibility that a desired injection rate may not be obtained at high load (particularly the WOT region) by reducing the fuel pressure in the homogeneous region. In the (fuel shortage region), in order to increase the fuel pressure and further suppress the Coanda effect, the fuel injection timing is delayed and the fuel is lifted during the opening period of the intake valve 6 at a timing after the valve lift of the intake valve 6 occurs. Is to inject. This is because if the intake valve 6 is lifted and positioned in the cylinder, it interferes with the Coanda effect.
[0060]
FIG. 13 is a flowchart of fuel pressure / back pressure control in the fourth embodiment, which corresponds to fuel pressure and back pressure control means.
Steps 101, 102, and 111 to 117 are the same as the flow of the third embodiment (FIG. 11), and steps 118 and 119 are added.
[0061]
In the case of the homogeneous region, the fuel pressure is set to a low fuel pressure. In step 118, it is determined whether or not the fuel is in a shortage region (WOT region).
As a result, in the case of the fuel shortage region, the routine proceeds to step 119, where the fuel pressure is increased and the intake valve opening-time injection in which fuel is injected during the opening period of the intake valve 6 is set. That is, the fuel pressure is set high so that a sufficient injection rate is obtained, and the fuel injection is started after the intake valve 6 is opened so that the Coanda effect does not occur, while the intake valve 6 is open. To finish the injection.
[0062]
With the above control, it is possible to suppress an increase in unburned fuel due to the Coanda effect while securing the injection rate in the WOT region. Therefore, unburned fuel can be suppressed without causing a decrease in output due to fuel shortage.
[0063]
Next, a fifth embodiment of the present invention will be described.
In the fifth embodiment, in the conceptual diagram of the fuel pressure / back pressure control in FIG. 10, the high fuel pressure and the high back pressure are set in the homogeneous region instead of the low fuel pressure and the low back pressure.
[0064]
FIG. 14 is a flowchart of fuel pressure / back pressure control in the fifth embodiment, which corresponds to fuel pressure and back pressure control means.
Steps 101, 102, 113 to 117 are the same as those in the third embodiment (FIG. 11), and different parts will be described.
[0065]
If the result of determination in step 102 is a homogeneous region, the process proceeds to step 111 ', the fuel pressure map for the homogeneous region is referenced, the fuel pressure is set to a relatively high fuel pressure according to the engine speed and load, At 112 ′, the fuel pressure is controlled.
[0066]
And it progresses to step 120, the opening degree of the electric control throttle valve 18 is correct | amended to an open side, and it sets to high back pressure. That is, the back pressure is controlled so as not to cause the Coanda effect.
[0067]
Thus, by setting the high back pressure at the time of homogeneous operation, it is possible to reduce the unburned amount without using the Coanda effect. In this case, since the fuel pressure can be increased, the output is not reduced due to fuel shortage.
[0068]
As a method of changing the back pressure at the time of fuel injection, in addition to correcting and controlling the opening degree of the electric throttle valve 18, when a variable valve device for the intake valve 6 is provided, the intake valve closing timing is controlled. By moving the intake valve closing timing to the top dead center side, the intake air amount is reduced, the back pressure is reduced, and by reducing the intake valve closing timing to the bottom dead center side, the intake air amount is increased, High back pressure is also possible.
[Brief description of the drawings]
FIG. 1 is a system diagram of a direct-injection spark-ignition internal combustion engine showing an embodiment of the present invention. FIG. 2 is a schematic plan view of the same internal combustion engine. FIG. 3 is a conceptual diagram showing the Coanda effect and the influence of fuel pressure. ] Schematic diagram of fuel pressure control according to the first embodiment. [FIG. 5] Flow chart of fuel pressure control according to the first embodiment. [FIG. 6] A diagram showing a spray form when using / not using the Coanda effect. FIG. 8 is a conceptual diagram of fuel pressure control according to the second embodiment. FIG. 9 is a conceptual diagram illustrating the Coanda effect and the influence of back pressure. FIG. 10 is a conceptual diagram of fuel pressure / back pressure control according to the third embodiment. 11 is a flowchart of fuel pressure / back pressure control according to the third embodiment. FIG. 12 is a conceptual diagram of fuel pressure / back pressure control according to the fourth embodiment. FIG. 13 is a flowchart of fuel pressure / back pressure control according to the fourth embodiment. FIG. 14 is a flow chart of fuel pressure / back pressure control according to the fifth embodiment. Chart DESCRIPTION OF SYMBOLS
DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cylinder block 3 Piston 4 Combustion chamber 5 Spark plug 6 Intake valve 7 Exhaust valve 8 Intake port 9 Exhaust port 10 Fuel injection valve 11 Concave part 12 Convex part (Coanda effect production | generation)
13 Control unit 14 Crank angle sensor 15 Accelerator opening sensor 16 Water temperature sensor 17 Pressure regulator 18 Electric throttle valve

Claims (6)

A spark plug that faces the combustion chamber from substantially the center of the cylinder head combustion chamber wall surface, and a fuel injection valve that faces the combustion chamber from a side of the cylinder head combustion chamber wall surface on the intake valve side. In a direct-injection spark ignition internal combustion engine in which fuel is injected from a fuel injection valve in a compression stroke under conditions to cause stratified combustion,
Providing a projection close to the fuel spray on the cylinder head combustion chamber wall surface between the fuel injection valve and the spark plug,
A direct-injection spark ignition comprising a control means for controlling at least one of a fuel pressure or an in-cylinder pressure at the time of fuel injection so as to change a fuel spray form by the convex portion according to an engine operating condition. Internal combustion engine. 2. The direct eruption according to claim 1, wherein, during stratified operation in which stratified combustion is performed, the control means sets a high fuel pressure at a low speed and a low fuel pressure at a high speed according to an engine speed. Flower ignition internal combustion engine. 2. The control device according to claim 1, wherein during the stratified operation in which stratified combustion is performed, the low in-cylinder pressure is set at a low speed and the high in-cylinder pressure is set at a high speed according to an engine speed. Direct-injection spark ignition internal combustion engine. The said control means makes low fuel pressure at the time of the homogeneous operation which injects a fuel from a fuel injection valve in an intake stroke, and performs homogeneous combustion, The fuel fuel pressure as described in any one of Claims 1-3 characterized by the above-mentioned. The direct-injection spark ignition internal combustion engine described. 5. The control means increases the fuel pressure in a region where the fuel injection amount is insufficient due to a low fuel pressure during homogeneous operation, and injects fuel while the intake valve is open. Direct-injection spark ignition internal combustion engine. The said control means makes high in-cylinder pressure at the time of the homogeneous operation which injects a fuel from a fuel-injection valve in an intake stroke, and performs homogeneous combustion, The any one of Claims 1-3 characterized by the above-mentioned. A direct-injection spark-ignition internal combustion engine as described in 1.

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