JP2917737B2 - Direct injection spark ignition engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct-injection spark ignition engine, and more particularly to an injection pressure control for controlling an air-fuel ratio near a spark plug immediately before ignition.

[0002]

2. Description of the Related Art In a premixed spark ignition engine having a carburetor and a fuel injection valve in an intake pipe, there is a problem that output characteristics and exhaust composition are deteriorated due to a delay in fuel transport especially during transient operation. In order to solve the above problem, a direct injection type spark ignition engine in which the injection hole of the fuel injection valve faces the combustion chamber and fuel is injected during the compression stroke by the fuel injection valve has been proposed (Japanese Patent Application No. Hei. 17738).

[0003]

In order to stabilize the ignition performance when performing lean combustion in the direct-injection spark ignition engine, the air-fuel ratio in the vicinity of the spark plug is made higher than in the other combustion chamber region. It is considered that stratification is effective, and for such stratification, it is conceivable that fuel injection is performed in the vicinity of the spark plug.

Here, if the fuel injection is performed by directing the fuel toward the vicinity of the spark plug, the fuel may directly cover the electrode portion of the spark plug, which may cause smoldering or misfire.
Here, in a direct injection type fuel injection valve, the injection pressure is a major factor that determines the reach of the combustion spray. Therefore, the injection pressure of the fuel injection valve that can increase the air-fuel ratio in the vicinity of the ignition plug within a range that does not cause fogging of the ignition plug. Setting is required.

[0005] However, irregular gas flows are formed in the combustion chamber, and due to the effect of the in-cylinder pressure, the reach of the fuel spray is not constant, and the fuel is injected under a constant injection pressure. This causes a problem that the desired air-fuel ratio cannot be stably formed in the vicinity of the ignition plug. That is, if the set injection pressure is too large and the reach is too long, fogging of the spark plug occurs.If the set injection pressure is too small and the reach is too short, an air-fuel ratio mixture that can be ignited is formed near the spark plug. It is not possible to cause a misfire. For this reason, it has been difficult to maximize the air-fuel ratio near the ignition plug while avoiding fogging of the ignition plug.

Therefore, in order to optimize the injection pressure in the direct injection spark ignition engine, the local air-fuel ratio near the spark plug in the combustion chamber is detected, and the air-fuel ratio near the spark plug is set to a target based on the detection result. It is desired to control the injection pressure so as to achieve the air-fuel ratio. As a method of detecting the local air-fuel ratio in the vicinity of the ignition plug, conventionally, as disclosed in Japanese Patent Laid-Open No. 1-247740, combustion light is extracted by an optical fiber embedded in the ignition plug, and the extracted combustion light is photoelectrically converted. There is a configuration in which the local air-fuel ratio near the spark plug is detected by conversion.

However, in the above-described detection of the local air-fuel ratio based on the combustion light, the air-fuel ratio is detected by the combustion light generated by the ignition combustion, and the air-fuel ratio immediately before the ignition, which indicates the injection pressure more appropriately, is determined. Since it cannot be detected, the change in the reach of the fuel spray due to the gas flow as described above, in other words, the air-fuel ratio formed in the vicinity of the spark plug cannot be detected with high accuracy, and the spark plug cannot be detected. There is a problem that it is difficult to stably obtain high ignitability while avoiding fogging.

The present invention has been made in view of the above-mentioned problems, and a fuel injection valve is provided such that an injection hole faces a combustion chamber and fuel spray from the injection hole is directed to a vicinity of an ignition plug. It is an object of the present invention to provide a direct injection type spark ignition engine capable of performing injection pressure control that can set an air-fuel ratio near an ignition plug immediately before ignition to an optimum value.

[0009]

Therefore, in the direct injection spark ignition engine according to the present invention, the injection hole of the fuel injection valve faces the combustion chamber, and the injection hole is disposed so as to face the vicinity of the spark plug. This is a direct injection spark ignition engine and is configured as shown in FIG. In FIG. 1, a transmitted light intensity detecting means is arranged such that a pair of optical elements each including a light emitting side and a light receiving side are opposed to each other with a predetermined gap facing a combustion chamber near an ignition plug, and light emitted from a light source is transmitted to the pair of optical elements. This is a means having a configuration for leading to a photoelectric conversion element via an optical element.

Further, the in-cylinder pressure detecting means detects the in-cylinder pressure of the engine, and the air-fuel ratio calculating means based on the output of the photoelectric conversion element in the transmitted light intensity detecting means and the in-cylinder pressure detected by the in-cylinder pressure detecting means. Calculate the air-fuel ratio near the spark plug. Then, the injection pressure control means controls the fuel injection so that the air-fuel ratio immediately before ignition calculated by the air-fuel ratio calculation means becomes the target air-fuel ratio.
Controlling the fuel injection pressure at the firing valve to reach the fuel spray
To change .

Here, in addition to the above configuration, the required fuel injection amount calculating means for calculating the required fuel injection amount based on the engine operating conditions and the required fuel injection amount calculated by the required fuel injection amount calculating means are injected. An injection time calculating means for calculating a required injection time based on the fuel injection pressure controlled by the injection pressure control means, and the injection being performed under a fuel injection pressure controlled by the injection pressure control means at a predetermined injection timing. It is preferable to provide an injection control means for opening and controlling the fuel injection valve for the injection time calculated by the time calculation means.

[0012]

According to this structure, in the transmitted light intensity detecting means, the light emitted from the light source is guided to the photoelectric conversion element through the gap between the pair of optical elements facing the combustion chamber near the ignition plug. When passing through the gap between the optical elements, the fuel is attenuated by the fuel existing in the space.

The attenuation varies depending on the fuel concentration, and the fact that the attenuation varies depending on the fuel concentration also varies depending on the pressure in the combustion chamber (in-cylinder pressure). Therefore, based on the output of the photoelectric conversion element, through which the transmitted light passing through the gap enters via the optical element, and the in-cylinder pressure detected by the in-cylinder pressure detecting means, the factors of the in-cylinder pressure are excluded and the vicinity of the ignition plug is removed. Fuel concentration (air-fuel ratio) is detected.

Here, the detection of the air-fuel ratio is performed through the absorption of light by the fuel existing near the spark plug in the combustion chamber, and the air-fuel ratio near the spark plug before ignition can be detected. . Therefore, near the spark plug just before ignition
The injection by the fuel injection valve is performed so that the air-fuel ratio becomes the target air-fuel ratio.
By controlling the injection pressure, the reaching distance of the fuel spray is controlled so that an air-fuel mixture having an air-fuel ratio that provides high ignitability while avoiding fuel fogging of the spark plug is formed near the spark plug.

If the injection pressure is controlled as described above, the injection amount per unit time changes according to the change in the injection pressure, and the injection time corresponding to the required injection amount changes. The injection time required to inject the required injection amount is calculated based on the injection pressure.

[0016]

Embodiments of the present invention will be described below. FIG. 2 is a diagram illustrating the system configuration of the present embodiment. In FIG. 2, the engine 1 has a new electromagnetic fuel injection valve 2 with its injection hole facing the combustion chamber 3 and suction into the combustion chamber 3 via the intake valve 4 during the intake stroke. This is a direct-injection spark ignition engine in which fuel is injected from the fuel injection valve 2 during a compression stroke to form air-fuel mixture, and the air-fuel mixture is ignited and burned by spark ignition by a spark plug 5.

The exhaust gas of the direct-injection spark ignition engine 1 is discharged from the combustion chamber 3 through an exhaust valve 6, and further discharged to the atmosphere through a catalyst and a muffler (not shown). The fuel injection valve 2 is supplied with gasoline fuel which is suction-fed from the fuel tank 7 by a fuel pump 8 and adjusted to a predetermined injection pressure by a pressure regulator 9. The fuel injection valve 2 is controlled to open in response to an injection pulse signal having a predetermined pulse width sent at a predetermined injection timing from a control unit 10 incorporating a microcomputer, and the fuel adjusted to the predetermined injection pressure is supplied into the combustion chamber 3. To be injected.

That is, the injection amount of the fuel injection valve 2 is determined by the injection pressure and the pulse width of the injection pulse signal corresponding to the injection time. The pressure regulator 9 is a pressure regulator of a variable set pressure type whose regulation pressure changes according to an injection pressure control signal from the control unit 10. The pressure regulator 9 changes the opening area of the return passage for returning the fuel into the fuel tank 7 from the middle of the fuel supply passage by electronic control and adjusts it to a predetermined injection pressure. The control unit 10 senses the pressure difference between the fuel pressure (injection pressure) supplied to the engine and the pressure in the combustion chamber, which is the location where the fuel is injected, based on the comparison result between the pressure difference and the target pressure. Control the opening area.

Here, the spray direction of the fuel injection valve 2 is as follows.
As shown in FIG. 3, it is directed to the vicinity of the spark plug 5, so that stratification in the combustion chamber can be performed in which a denser air-fuel ratio is formed near the spark plug than the others.
That is, in the case where lean combustion is performed by the direct injection spark ignition engine of the present embodiment, even if the average air-fuel ratio in the combustion chamber is a lean air-fuel ratio having poor ignition stability, the fuel is directed toward the ignition plug 5. By injecting, the air-fuel ratio in the vicinity of the ignition plug is made richer than the others, so that ignition stability can be ensured.

The direct-injection spark ignition engine 1 has the following configuration for detecting the local air-fuel ratio in the vicinity of the ignition plug 5 in the combustion chamber 3. That is, the ignition plug 5 is integrally provided with a pair of optical elements for guiding the light beam into the combustion chamber 3 and extracting the light beam transmitted through the space inside the combustion chamber 3 to the outside. The pair of optical elements provided integrally with the ignition plug 5 are shown in FIGS.
As shown in (1), the laser light emitted from the external laser source (light source) 11 is guided to a position facing the inside of the combustion chamber 3 at the tip of the ignition plug 5, and an optical element provided at the tip facing the combustion chamber 3 surface
An optical element 12 on the light emitting side that reflects laser light toward the other optical element 13 by 12a is disposed to face the optical element 12 with a predetermined gap therebetween, and is reflected by an optical surface 12a at the tip of the optical element 12. The optical surface 13a which receives the laser light thus incident and reflects the incident light toward the base end side of the ignition plug 5
And a light receiving side optical element 13 for guiding the laser light reflected by the optical surface 13a to the outside.

That is, the front ends of the pair of optical elements 12 and 13 face the combustion chamber 3, respectively, and the front ends are opposed to each other with a predetermined gap therebetween, and the optical surfaces provided at the respective front ends are provided. The laser light emitted from the laser source 11 is transmitted through the gap space (space in the combustion chamber) between the optical elements 12 and 13 by the laser beams 12a and 13a, and the transmitted light is extracted to the outside.

The laser light taken out of the combustion chamber 3 through the optical element 13 is incident on a photoelectric conversion element 14, and the transmitted light intensity of the laser light is detected by the photoelectric conversion element 14. It has become. Here, the optical elements 12 and 13 are opposed to each other with the center electrode 5a of the ignition plug 5 as a center. With this configuration, the gap between the pair of optical elements 12 and 13 is It crosses the spark gap sandwiched between 5a and the ground electrode 5b. Therefore, the laser light transmitted from the optical element 12 to the optical element 13 in the combustion chamber space travels across the spark gap.

In FIG. 2, reference numeral 15 designates a laser beam emitted from the laser source 11 reflected by the optical element 12 and a laser beam extracted via the optical element 13 reflected by the photoelectric conversion element 14.
The laser source 11, the optical elements 12, 13, the optical component 15, and the photoelectric conversion element 14 constitute the transmitted light intensity detecting means of the present embodiment.

As the material of the optical elements 12 and 13, quartz or sapphire can be used, but sapphire is preferably used in consideration of heat resistance and pressure resistance. Further, the combustion chamber 3 determined by the arrangement of the optical elements 12 and 13
It is preferable that the transmission space of the laser light in the inside is in the vicinity of the spark gap of the ignition plug 5, but the optical path of the laser light is not limited to the arrangement of the optical element crossing the spark gap.
Further, a configuration in which the optical elements 12 and 13 are provided separately from the ignition plug 5 may be employed.

As a light beam emitted by the laser source 11, a laser beam having a wavelength selectively absorbed by gasoline fuel to be used is used. Specifically, the light is infrared light. In this embodiment, a laser light having a wavelength of 3.39 μm included in the infrared light region is used. The gasoline fuel used for the engine 1 generally has a property of selectively absorbing infrared light, and the amount of absorption in a mixture increases substantially in proportion to the gasoline concentration in the mixture. That is, assuming that the incident light intensity is I _O , the gasoline concentration is C, and the absorption coefficient is K, the absorption amount I of infrared light by gasoline can be expressed as I = I _O exp ^−KC .

Therefore, if the mixture is irradiated with infrared light of a predetermined intensity and it is possible to detect how much the infrared light has been absorbed by the gasoline, the gasoline concentration in the mixture, in other words, the emptyness of the mixture, The fuel ratio can be detected. Here, in the present embodiment, the pair of optical elements 12 and 13 are opposed to each other with a space in the combustion chamber 3 as a gap, and the laser beam passes through the gap and finally enters the photoelectric conversion element 14. Since the laser light travels across the spark gap of the spark plug 5, the laser light is absorbed by an amount corresponding to the gasoline concentration in the air-fuel mixture present in the spark gap, and is attenuated by the absorption. The laser light enters the photoelectric conversion element 14.

The fact that the amount of absorption of laser light (infrared light) is proportional to the gasoline concentration means that the amount of absorption also changes due to a change in pressure (in-cylinder pressure) in the combustion chamber. Therefore, the calibration characteristic based on the in-cylinder pressure is measured in advance (see FIG. 6), and the output of the photoelectric conversion element 14 and the in-cylinder pressure detected by the in-cylinder pressure sensor 16 as the in-cylinder pressure detecting means are used as parameters. By setting the air-fuel ratio calculation characteristics (conversion map) in advance, the air-fuel ratio around the spark gap of the spark plug 5 can be calculated from the intake stroke in which the air-fuel mixture is sucked to the ignition timing (FIG. 7).

Here, since the fuel injection by the fuel injection valve 2 is directed toward the spark plug 5, the injected fuel directly covers the electrode portion of the spark plug 5 and causes smoldering and misfire. It is desired that the air-fuel ratio near the ignition plug 5 be made as rich as possible to improve the ignition performance. However, an irregular gas flow is formed in the combustion chamber, and also due to the influence of the in-cylinder pressure, the reaching distance of the fuel spray is not constant, and the setting injection pressure of the fuel injection valve 2 is excessive and the reaching distance is large. If it is too long, the ignition plug will fog, and if the set injection pressure is too small and the reach is too short,
An ignitable air-fuel mixture cannot be formed in the vicinity of the ignition plug 5, causing a misfire.

Therefore, the control unit 10 detects the air-fuel ratio immediately before ignition in the vicinity of the ignition plug 5 by the above configuration, and adjusts the pressure based on the detection result so that the air-fuel ratio in the vicinity of the ignition plug 5 becomes the target air-fuel ratio. The injection pressure adjusted by the heater 9 is controlled. Therefore, in addition to the output of the photoelectric conversion element 14, the control unit 10 includes an in-cylinder pressure sensor 16, a crank angle sensor 17, and an air flow meter.
A detection signal is input from the sensor 18 and an air-fuel ratio is calculated based on an output of the photoelectric conversion element 14 and a detection signal of the in-cylinder pressure sensor 16.
Is controlled, and the pulse width of the injection pulse signal to be given to the fuel injection valve 2 in accordance with the injection pressure control is set.

Next, how the control unit 10 detects the air-fuel ratio and controls the injection will be described in detail with reference to the flowchart of FIG. In this embodiment, the functions of the air-fuel ratio calculation means, the injection pressure control means, the required injection amount calculation means, the injection time calculation means and the injection control means are performed by the control unit 10 as shown in the flowchart of FIG. Provided as software.

In the flowchart of FIG. 8, the engine speed Ne is calculated based on the rotation signal from the crank angle sensor 17 in S1, and the intake air amount detected by the air flow meter 18 is read in S2. Then, in S3, when the basic injection pulse width (injection time) corresponding to the required injection amount is adjusted to the basic injection pressure Po corresponding to the engine operating condition, based on the information of the rotation and the air amount (load). Calculate accordingly.

At S4, the ignition timing is obtained from the map based on the information on the rotation and the load. In the next step S5, a basic injection pressure Po set in advance according to operating conditions such as the engine speed is set, and is adjusted to the basic injection pressure Po by the pressure regulator 9. still,
The basic injection pressure Po is, in detail, a target differential pressure between the injection pressure and the in-cylinder pressure. Hereinafter, the description will be simplified simply as the injection pressure.

In S6, the fuel injection valve 2 is controlled to open at a predetermined injection timing in accordance with the set basic injection pulse width (the injection time corresponding to the required injection amount calculated corresponding to the basic injection pressure Po). , And perform fuel injection.
In S7, the air-fuel ratio calculated based on the transmitted light intensity of the laser beam and the in-cylinder pressure detected by the in-cylinder pressure sensor 16 is sampled according to the ignition timing obtained in S4, and the air-fuel ratio near the ignition plug 5 immediately before ignition is sampled. The fuel ratio Ao is obtained.

In step S8, the air-fuel ratio Ao is compared with a lean limit value Amin of the ignitable air-fuel ratio. When the air-fuel ratio Ao near the ignition plug 5 immediately before ignition is leaner than the lean limit value Amin, the process proceeds to S9, and a correction is made to increase the injection pressure by a predetermined value. In the injection pressure correction control, 1/10 of the basic injection pressure Po is used.
It is good to change the pressure of about 0 stepwise.

That is, when the air-fuel ratio near the spark plug 5 immediately before ignition is leaner than the desired air-fuel ratio, the injection pressure is lower than required, and the fuel spray reaches the vicinity of the injection valve as required. It can be estimated that they did not. Therefore, by performing a correction that further increases the injection pressure, the reaching distance of the fuel injected from the injection valve 2 is extended, the air-fuel ratio near the ignition plug 5 immediately before ignition is further enriched, and the air that provides good ignition is obtained. The ignition is performed in the fuel ratio atmosphere.

On the other hand, when it is determined in S8 that the air-fuel ratio Ao near the ignition plug 6 immediately before ignition is richer than the lean limit value Amin, the process proceeds to S10, and this time the air-fuel ratio Ao and the ignitable air-fuel ratio are compared. Compare with the rich limit value Amax. Here, when it is determined that the air-fuel ratio Ao in the vicinity of the ignition plug 5 immediately before ignition is richer than the rich limit value Amax, the process proceeds to S11, and a correction is made to reduce the injection pressure by a predetermined value.

That is, when the atmosphere of the ignition plug 5 is the rich limit value A
In the case of a rich atmosphere exceeding max, the fuel injection distance from the fuel injection valve 2 is too long and the ignition plug 5
It is presumed that the fuel spray directly hits and causes wetting, so the injection distance is reduced by lowering the injection pressure, and the air-fuel ratio near the ignition plug 5 immediately before ignition is made lean.

If the injection pressure is changed in S9 or S11, the desired fuel cannot be injected unless the injection pulse width is corrected according to the change in the injection pressure.
A process for correcting the injection pulse width (injection time) according to the injection pressure changed in 12 is performed. Then, in S13, the S
The injection pressure P ₁ (target differential pressure) changed in 9 or S11 is set to the adjustment pressure Po in the pressure regulator 9.

On the other hand, according to the discrimination in S8 and S10, the air-fuel ratio Ao is changed between the lean limit value Amin and the rich limit value A.
If it is determined that it is within the required air-fuel ratio (target air-fuel ratio) range sandwiched by max, it is not necessary to correct the injection pressure, so that S9 to S13 are jumped to maintain the current injection pressure, and S14 is performed. Proceed to. Here, the characteristics of the injection pressure control in the above embodiment are shown in FIG. That is, the lean limit value Amin
If the air-fuel ratio in the vicinity of the spark plug immediately before ignition falls within the range of the ignitable air-fuel ratio between the ignition limit and the rich limit value Amax, the injection pressure at that time is maintained, and the lean limit value Ami
When the lean air-fuel ratio is lower than n, the injection pressure is increased and controlled within the control range (Pmax-Pmin). Injection pressure is reduced.

In step S14, it is determined whether or not the operating conditions (rotation, load) have changed. If the operating conditions are constant and the required fuel amount is constant, the process returns to step S6, and the vicinity of the ignition plug 5 immediately before the ignition is started. The injection pressure adjustment for controlling the air-fuel ratio within the required range is performed again. On the other hand, if the required fuel amount changes due to a change in the operating conditions, the process returns to S1 to calculate the required fuel amount.

According to the above embodiment, the injection pressure of the direct injection type fuel injection valve 2 is adjusted so that the air-fuel ratio near the ignition plug 5 immediately before ignition becomes an air-fuel ratio optimum for ignition. Ignition can be performed under various air-fuel ratio conditions. Therefore, even when performing lean combustion,
By injecting fuel in the vicinity of the spark plug 5 and injecting fuel, an air-fuel mixture with a richer air-fuel ratio is formed near the spark plug, and stably at a rich air-fuel ratio while avoiding fogging of the spark plug. Controllable and stable ignition performance can be obtained during lean burn.

Further, by stratification of the air-fuel mixture, the air-fuel ratio becomes extremely lean in a region far from the ignition plug 5 in the combustion chamber 3 and the self-ignition reaction leading to knocking is suppressed.
As a result, the compression ratio can be increased, and the thermal efficiency and output can be improved. The injection pressure adjustment based on the injection pressure set based on the detection result of the air-fuel ratio may be performed by drive control of the fuel pump, and the method of adjusting the injection pressure is the method by the pressure regulator 9 of the above embodiment. It is not limited to.

In the above embodiment, the detection result of the air-fuel ratio is used only for adjusting the injection pressure. However, a configuration in which the fuel injection amount is subjected to feedback correction based on the detection result of the air-fuel ratio based on the transmitted light intensity of the laser light. It is good.

[0044]

As described above, according to the present invention, in a direct injection type spark ignition engine having a fuel injection valve having an injection hole facing the combustion chamber, fuel is directed in the vicinity of the spark plug, and the fuel injection valve is located near the spark plug. air-fuel of the transmitted intensity of the light is transmitted through the combustion chamber space to detect the air-fuel ratio at the ignition immediately before the vicinity of the spark plug, in the vicinity of the spark plug ignition immediately before on the basis of the detection result
Injection pressure by the fuel injector so that the ratio becomes the target air-fuel ratio
Control the fuel spray distance by controlling
By doing so, while avoiding fuel fogging of the spark plug,
The air-fuel ratio in the vicinity of the spark plug immediately before ignition can be controlled to an air-fuel ratio at which a high ignitability can be obtained, and there is an effect that the ignition performance particularly when performing lean combustion can be enhanced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a diagram showing the direction of fuel spray in the embodiment.

FIG. 4 is an enlarged side view of the tip portion of the ignition plug in the embodiment.

FIG. 5 is an enlarged bottom view of the tip of the spark plug in the embodiment.

FIG. 6 is a diagram showing an air-fuel ratio corresponding to transmitted light intensity and in-cylinder pressure.

FIG. 7 is a diagram showing changes in in-cylinder pressure and transmitted light intensity with respect to a crank angle.

FIG. 8 is a flowchart showing injection pressure control in the embodiment.

FIG. 9 is a diagram showing characteristics of injection pressure control in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Direct injection spark ignition engine 2 Fuel injection valve 3 Combustion chamber 4 Intake valve 5 Spark plug 5a Center electrode 5b Ground electrode 7 Fuel tank 8 Fuel pump 9 Pressure regulator 10 Control unit 11 Laser source 12, 13 Optical element 14 Photoelectric conversion element 16 Cylinder pressure sensor 17 Crank angle sensor 18 Air flow meter

Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI G01N 21/61 G01N 21/61 (56) References JP-A-1-237435 (JP, A) JP-A-62-87638 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/14 310 F02D 41/02 345 F02D 41/32 F02D 45/00 364 F02D 45/00 368 G01N 21/61

Claims (2)

(57) [Claims] 1. A direct-injection spark ignition engine in which an injection hole of a fuel injection valve faces a combustion chamber, and wherein the injection hole is disposed so as to face a vicinity of a spark plug, wherein the combustion chamber is close to the spark plug. A pair of optical elements consisting of a light-emitting side and a light-receiving side facing each other are disposed facing each other with a predetermined gap, and transmitted light intensity detecting means for guiding light emitted by a light source to a photoelectric conversion element through the pair of optical elements, An in-cylinder pressure detecting means for detecting an in-cylinder pressure of the engine; and calculating an air-fuel ratio near the ignition plug based on an output of the photoelectric conversion element in the transmitted light intensity detecting means and an in-cylinder pressure detected by the in-cylinder pressure detecting means. air-fuel ratio calculating means and the target air-fuel ratio of the ignition immediately before is computed by the air-fuel ratio calculating means for
Fuel injection at the fuel injection valve so as to achieve an air-fuel ratio
A direct-injection spark ignition engine, comprising: an injection pressure control means for controlling a pressure to change a reaching distance of the fuel spray . 2. A required fuel injection amount calculating means for calculating a required fuel injection amount based on engine operating conditions; and an injection time required for injecting the required fuel injection amount calculated by the required fuel injection amount calculating means. An injection time calculating means for calculating based on the fuel injection pressure controlled by the injection pressure control means; and a fuel injection pressure calculated by the injection time control means at a predetermined injection timing under the fuel injection pressure controlled by the injection pressure control means. The direct-injection spark ignition engine according to claim 1, further comprising: injection control means for opening and controlling the fuel injection valve for a predetermined injection time.