JPH06288282A - Direct injection type spark ignition engine - Google Patents

Abstract

PURPOSE:To control properly injection pressure of fuel in a fuel injection valve so as to improve ignition performance, in a direct injection type spark ignition engine for allowing injection of fuel while making the fuel injection valve to point to the vicinity of a sparking plug there by the injection hole of the fuel injection valve is arranged in a fuel chamber. CONSTITUTION:Laser beam having a wave length absorbed selectively by gasoline is led in a combustion chamber, and passed into a space in the combustion chamber positioned in the vicinity of a sparking plug. lntensity of transmitting beam is detected by a photoelectric transfer element, and an air-fuel ratio in the vicinity of the sparking plug just before ignition is calculated on the basis of the intensity of transmitting beam and internal cylinder pressure (S7). When calculated air-fuel ratio is in a condition leaner than a prescribed lean limit air-fuel ratio, injection pressure is increased (S8 S9), and on the other hand, when the calculated air-fuel ratio is in condition richer than a prescribed rich limit air-fuel ratio, injection pressure is reduced (S10 S11).

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 injection pressure control for controlling the air-fuel ratio near the ignition plug immediately before ignition.

[0002]

2. Description of the Related Art A premixed spark ignition engine having a carburetor and a fuel injection valve in an intake pipe has a problem that output characteristics and exhaust composition are deteriorated due to delay in fuel transportation, especially during transient operation. In order to solve the above problem, there has been considered a direct injection spark ignition engine having a structure in which the injection hole of the fuel injection valve faces the combustion chamber and the fuel injection valve performs fuel injection during the compression stroke (Japanese Patent Application No. 4- 17738).

[0003]

By the way, in order to stabilize the ignition performance when performing lean combustion in the direct injection type spark ignition engine, the air-fuel ratio near the spark plug should be made higher than that in other combustion chamber regions. Stratification is effective, and for such stratification, it is conceivable that the fuel is injected toward the vicinity of the spark plug.

If the fuel injection is performed by directing it toward the vicinity of the spark plug, the fuel may directly cover the electrode part of the spark plug, causing smoldering or misfire.
Here, in a direct injection type fuel injection valve, the injection pressure is a major factor that determines the arrival distance of the combustion spray, so the injection pressure of the injection pressure that can thicken the air-fuel ratio in the vicinity of the spark plug within the range that does not cause fog of the spark plug. Settings are required.

However, due to the irregular gas flow formed in the combustion chamber and the influence of the in-cylinder pressure, the arrival distance of the fuel spray is not constant, and the fuel is injected under a constant injection pressure. If so, there is a problem that the desired air-fuel ratio cannot be stably formed in the vicinity of the spark plug. That is, if the set injection pressure is too high and the reaching distance is too long, the spark plug is fogged, and if the set injection pressure is too small and the reaching distance is too short, a mixture of air-fuel ratio that can ignite is formed near the spark plug. It may not be possible to cause misfire. Therefore, it has been difficult to maximize the air-fuel ratio in the vicinity of the spark plug while avoiding the spark plug fogging.

Therefore, in order to optimize the injection pressure in the direct injection spark ignition engine, the local air-fuel ratio in the vicinity of the spark plug in the combustion chamber is detected, and the air-fuel ratio in the vicinity of the spark plug is targeted based on the detection result. It is desirable to control the injection pressure so that the air-fuel ratio is achieved. As a method for detecting the local air-fuel ratio in the vicinity of the spark plug, conventionally, as disclosed in JP-A-1-247740, combustion light is extracted by an optical fiber embedded in the spark 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 detection of the local air-fuel ratio based on the above combustion light, the air-fuel ratio is detected by the combustion light generated by the ignition combustion, and the air-fuel ratio immediately before ignition, which shows the appropriateness of the injection pressure more accurately, is detected. Since it cannot be detected, it is impossible to accurately detect the change in the reaching distance 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. 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 problems, and the fuel injection valve is arranged so that the injection hole faces the combustion chamber and the fuel spray from the injection hole is directed near the ignition plug. It is an object of the present invention to provide a direct injection spark ignition engine that can perform injection pressure control that can optimize the air-fuel ratio near the spark plug immediately before ignition.

[0009]

Therefore, in the direct injection type 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 arranged in the vicinity of the spark plug. This is a direct injection spark ignition engine, which is configured as shown in FIG. In FIG. 1, the transmitted light intensity detecting means faces a combustion chamber in the vicinity of the spark plug, and arranges a pair of optical elements consisting of a light emitting side and a light receiving side so as to face each other with a predetermined gap, and the light emitted from the light source is arranged to It is a means for guiding the photoelectric conversion element through the optical element.

Further, the in-cylinder pressure detecting means detects the in-cylinder pressure of the engine, and the air-fuel ratio calculating means determines the in-cylinder pressure detected by the in-cylinder pressure detecting means in the transmitted light intensity detecting means. Calculate the air-fuel ratio near the spark plug. The injection pressure control means controls the fuel injection pressure in the fuel injection valve based on the air-fuel ratio immediately before ignition calculated by the air-fuel ratio calculation means.

Here, in addition to the above-mentioned structure, a required injection amount calculation means for calculating the required fuel injection amount based on the engine operating condition and a required fuel injection amount calculated by the required injection amount calculation means are injected. Injection time calculation means for calculating a required injection time based on the fuel injection pressure controlled by the injection pressure control means, and the injection under the 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 controlling the opening of 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 of the optical element, the fuel existing in the space is attenuated.

The attenuation changes depending on the fuel concentration, and the fact that it changes depending on the fuel concentration also changes depending on the pressure in the combustion chamber (cylinder pressure). Therefore, based on the output of the photoelectric conversion element in which the transmitted light that has passed through the gap enters through the optical element and the in-cylinder pressure detected by the in-cylinder pressure detecting means, the cause of the in-cylinder pressure is excluded and the vicinity of the spark plug is eliminated. The fuel concentration (air-fuel ratio) is detected.

Here, the air-fuel ratio detection is performed through the absorption of light by the fuel existing in the vicinity of the spark plug in the combustion chamber, and the air-fuel ratio near the spark plug before ignition can be detected. . Therefore, based on the detection result of the air-fuel ratio, the injection pressure by the fuel injection valve is controlled so that the air-fuel ratio in the vicinity of the ignition plug immediately before ignition, which is affected by the gas flow and fluctuates, becomes a predetermined air-fuel ratio. An air-fuel mixture having an air-fuel ratio that can obtain high ignitability while avoiding fuel fog is formed near the spark plug.

Further, when the injection pressure is controlled as described above, the injection amount per unit time changes according to the change of 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]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a diagram showing the system configuration of this embodiment. In FIG. 2, the engine 1 has an electromagnetic fuel injection valve 2 arranged so that its injection hole faces the combustion chamber 3 and sucked into the combustion chamber 3 via the intake valve 4 during the intake stroke. A direct injection type spark ignition engine in which fuel is injected from the fuel injection valve 2 to form air-fuel mixture during the compression stroke, and the air-fuel mixture is ignited and burned by spark ignition by a spark plug 5.

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

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 set pressure variable type pressure regulator whose regulated pressure changes according to an injection pressure control signal from the control unit 10. The pressure regulator 9 adjusts the opening area of the return passage for returning the fuel into the fuel tank 7 from the middle of the fuel supply passage to a predetermined injection pressure by changing the opening area by electronic control, for example. The pressure difference between the fuel pressure (injection pressure) supplied to the fuel cell and the pressure in the combustion chamber where the fuel is injected, and the control unit 10 detects the pressure difference in the return passage 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 shown in FIG. 3, it is directed to the vicinity of the spark plug 5, so that stratification can be performed in the combustion chamber in which an air-fuel ratio that is richer than the others is formed in the vicinity of the spark plug.
That is, in the case of performing lean combustion in the direct injection spark ignition engine of the present embodiment, even if the lean air-fuel ratio in which the ignition stability is poor as the average air-fuel ratio in the combustion chamber, the fuel is directed toward the spark plug 5. By injecting, the air-fuel ratio in the vicinity of the spark plug is made thicker than the others, thereby ensuring ignition stability.

Further, the direct injection spark ignition engine 1 is provided with the following structure for detecting the local air-fuel ratio in the vicinity of the spark plug 5 in the combustion chamber 3. That is, the spark plug 5 is integrally provided with a pair of optical elements for guiding the light beam into the combustion chamber 3 and taking out the light beam transmitted through the inner space of the combustion chamber 3 to the outside. The pair of optical elements provided integrally with the spark plug 5 are as shown in FIGS.
As shown in, 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 spark plug 5, and an optical provided at the tip facing the inside of the combustion chamber 3. surface
The optical element 12 on the light emitting side that reflects the laser beam toward the other optical element 13 by 12a and the optical element 12 are disposed to face each other with a predetermined gap, and are reflected by the optical surface 12a at the tip of the optical element 12. The combustion chamber 3 is provided with an optical surface 13a for injecting the generated laser light and reflecting the incident light toward the base end side of the spark plug 5.
It is provided with an optical element 13 on the light receiving side that is provided at the front end facing inward and guides the laser light reflected by the optical surface 13a to the outside.

That is, the tips of the pair of optical elements 12 and 13 respectively face the inside of the combustion chamber 3, and the tips are arranged so as to face each other with a predetermined gap, and the optical surfaces provided at the tips. After the laser light emitted from the laser source 11 is transmitted to the gap space (the space inside the combustion chamber) between the optical elements 12 and 13 by 12a and 13a, the transmitted light is extracted to the outside.

The laser light extracted from the inside of the combustion chamber 3 through the optical element 13 enters a photoelectric conversion element 14, and the photoelectric conversion element 14 detects the transmitted light intensity of the laser light. Has become. Here, the optical elements 12 and 13 are arranged so as to face each other with the center electrode 5a of the spark plug 5 as the center, and with this configuration, the gap between the pair of optical elements 12 and 13 is the center electrode of the spark plug 5. It crosses the spark gap sandwiched between 5a and the ground electrode 5b. Therefore, the laser light that passes through the combustion chamber space from the optical element 12 toward the optical element 13 travels across the spark gap.

In FIG. 2, reference numeral 15 reflects the laser light emitted from the laser source 11 to the optical element 12 side, and the laser light extracted via the optical element 13 is converted into a photoelectric conversion element 14.
The laser source 11, the optical elements 12 and 13, the optical component 15, and the photoelectric conversion element 14 are optical components including a mirror and a prism for reflecting the light toward the optical axis.

Quartz, sapphire or the like can be used as the material of the optical elements 12 and 13, but sapphire is preferably used in consideration of heat resistance and pressure resistance. Furthermore, the combustion chamber 3 determined by the arrangement of the optical elements 12 and 13
It is preferable that the laser light transmission space inside the spark plug be near the spark gap of the spark plug 5, but the optical path of the laser light is not limited to the arrangement of the optical elements that cross the spark gap.
Alternatively, the optical elements 12 and 13 may be provided separately from the spark plug 5.

As the light beam emitted by the laser source 11, a laser beam having a wavelength that is selectively absorbed by the gasoline fuel used is used. Specifically, it is infrared light, and in this embodiment, laser light having a wavelength of 3.39 μm included in the infrared light region is used. The gasoline fuel used in the engine 1 generally has a property of selectively absorbing infrared light, and in the air-fuel mixture, the absorption amount increases substantially in proportion to the gasoline concentration in the air-fuel mixture. That is, when 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 it is possible to irradiate the air-fuel mixture with infrared light of a predetermined intensity and detect how much the infrared light is absorbed by the gasoline, the concentration of gasoline in the air-fuel mixture, in other words, the sky of the air-fuel mixture is detected. The fuel ratio can be detected. Here, in the present embodiment, the pair of optical elements 12 and 13 are arranged so as to face each other with the space in the combustion chamber 3 as a gap, and the laser light 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 in an amount commensurate with the concentration of gasoline in the air-fuel mixture existing in the spark gap and is attenuated by the absorption. The laser light will enter the photoelectric conversion element 14.

Further, the fact that the absorption amount of the laser light (infrared light) is proportional to the gasoline concentration means that the absorption amount also changes due to the pressure (cylinder pressure) change 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 calculation characteristic (conversion map) of the air-fuel ratio in advance, it is possible to calculate the air-fuel ratio around the spark gap of the spark plug 5 during the intake stroke in which the air-fuel mixture is sucked up to the ignition timing. 7).

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, causing smoldering and misfire. It is desired that the air-fuel ratio near the spark plug 5 is made as rich as possible to improve the ignition performance. However, due to the irregular gas flow formed in the combustion chamber and the influence of the in-cylinder pressure, the reaching distance of the fuel spray is not constant, and the set injection pressure of the fuel injection valve 2 is excessive and the reaching distance is too long. If it is too long, fogging of the spark plug will occur, and if the set injection pressure is too small and the reaching distance is too short,
An air-fuel mixture with an ignitable air-fuel ratio cannot be formed in the vicinity of the spark plug 5, resulting in misfire.

Therefore, the control unit 10 detects the air-fuel ratio in the vicinity of the spark plug 5 immediately before ignition by the above-mentioned configuration, and adjusts the pressure so that the air-fuel ratio in the vicinity of the spark plug 5 becomes the target air-fuel ratio based on the detection result. The injection pressure adjusted by the device 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, an air flow meter.
The detection signal from 18 is input, the air-fuel ratio is calculated based on the output of the photoelectric conversion element 14 and the detection signal of the in-cylinder pressure sensor 16, and the pressure regulator 9 is calculated based on the calculation result.
The injection pressure adjusted by is controlled, and the pulse width of the injection pulse signal given to the fuel injection valve 2 according to the injection pressure control is set.

Next, the state of air-fuel ratio detection and injection control by the control unit 10 will be described in detail with reference to the flowchart of FIG. In the present 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 controlled by the control unit 10 as shown in the flow chart of FIG. It is equipped with 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 according to the engine operating condition based on the information on the rotation and the air amount (load). Calculate correspondingly.

Further, in S4, the ignition timing is obtained from the map based on the information on the rotation and the load. In the next S5, the basic injection pressure Po, which is set in advance in accordance with the operating conditions such as the engine speed, is set and adjusted by the pressure adjuster 9 to the basic injection pressure Po. still,
In detail, the basic injection pressure Po is a target differential pressure between the injection pressure and the in-cylinder pressure, but in the following, the explanation will be simplified simply as an injection pressure.

Then, in S6, the fuel injection valve 2 is controlled to open at a predetermined injection timing according to the set basic injection pulse width (injection time corresponding to the required injection amount calculated corresponding to the basic injection pressure Po). , Make fuel injection.
In S7, the air-fuel ratio calculated based on the transmitted light intensity of the laser light 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. Obtain the fuel ratio Ao.

In S8, the air-fuel ratio Ao is compared with the lean limit value Amin of the ignitable air-fuel ratio. Then, when the air-fuel ratio Ao in the vicinity of the spark plug 5 immediately before ignition is leaner than the lean limit value Amin, the routine proceeds to S9, where correction is performed to increase the injection pressure by a predetermined value. In the correction control of the injection pressure, 1/10 of the basic injection pressure Po
It is advisable to change the pressure of about 0 stepwise.

That is, when the air-fuel ratio in the vicinity of the spark plug 5 immediately before ignition is leaner than the desired air-fuel ratio, the injection pressure is lower than required, so that the fuel spray reaches the vicinity of the injection valve as required. It can be inferred that they have not. Therefore, by performing a correction to increase the injection pressure, the arrival distance of the fuel injected from the injection valve 2 is extended, the air-fuel ratio near the spark plug 5 immediately before ignition is made richer, and good ignition is obtained. Ignition is performed in a fuel ratio atmosphere.

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

That is, the atmosphere of the spark plug 5 has a rich limit value A.
In a rich atmosphere exceeding max, the distance reached by the fuel injected from the fuel injection valve 2 is too long and the spark plug 5
Since it is estimated that the fuel spray directly hits and causes wetting, the reaching distance is shortened by lowering the injection pressure, and the air-fuel ratio near the spark plug 5 immediately before ignition is made lean.

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

On the other hand, the air-fuel ratio Ao is determined to be lean limit value Amin and rich limit value A by the determinations in S8 and S10.
If it is determined that the current injection pressure is within the required air-fuel ratio range sandwiched by max, it is not necessary to correct the injection pressure, and therefore, steps S9 to S13 are jumped to maintain the current injection pressure, and the process proceeds to S14. Here, the characteristics of the injection pressure control in the above embodiment are shown in FIG. That is, the lean limit value Amin and the rich limit value A
If the air-fuel ratio in the vicinity of the spark plug just before ignition falls within the ignitable air-fuel ratio range sandwiched by max, the injection pressure at that time is maintained, and when the lean air-fuel ratio is below the lean limit value Amin, The injection pressure is controlled to increase within the control range (Pmax to Pmin), and when the rich air-fuel ratio exceeds the rich limit value Amax, the injection pressure is within the control range (Pmax to Pmin).
Pmin) controls the injection pressure to decrease.

In S14, it is determined whether or not the operating conditions (rotation, load) have changed, and if the operating conditions are constant and the required fuel amount is constant, the process returns to S6 and the vicinity of the spark plug 5 immediately before ignition is determined. The injection pressure is adjusted again to control the air-fuel ratio within the required range. On the other hand, when the operating condition changes and the required fuel amount changes, the process returns to S1 and the required fuel amount is calculated.

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

Further, due to the stratification of the air-fuel mixture, the air-fuel ratio becomes extremely lean in the region far from the spark 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 thermal efficiency and output can be improved. It should be noted that 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 injection pressure is adjusted by the pressure adjuster 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, but the fuel injection amount is feedback-corrected based on the detection result of the air-fuel ratio based on the transmitted light intensity of the laser light. Also good.

[0044]

As described above, according to the present invention, in the direct injection type spark ignition engine having the structure in which the fuel injection valve having the injection hole facing the combustion chamber directs the fuel toward the vicinity of the spark plug to inject the fuel, The fuel of the spark plug is detected by detecting the air-fuel ratio immediately before ignition in the vicinity of the spark plug based on the transmission intensity of the light transmitted through the combustion chamber space and controlling the injection pressure of the fuel injection valve based on the detection result. While avoiding fogging,
There is an effect that the air-fuel ratio in the vicinity of the spark plug immediately before ignition can be controlled to an air-fuel ratio that can obtain high ignitability, and the ignition performance can be enhanced especially when performing lean combustion.

[Brief description of drawings]

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

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

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

FIG. 4 is an enlarged side view of a spark plug tip portion according to the embodiment.

FIG. 5 is an enlarged bottom view of a spark plug tip portion according to 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]

 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 In-cylinder pressure sensor 17 Crank angle sensor 18 Air flow meter

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G01N 21/59 Z 7370-2J

Claims (2)

[Claims] 1. A direct injection type spark ignition engine in which a nozzle hole of a fuel injection valve faces a combustion chamber, and the nozzle hole is arranged so as to face the vicinity of the spark plug, and the combustion chamber near the spark plug. A pair of optical elements consisting of a light emitting side and a light receiving side facing each other with a predetermined gap therebetween, and transmitted light intensity detecting means for guiding the light emitted from the light source to the photoelectric conversion element via the pair of optical elements, An in-cylinder pressure detecting means for detecting the in-cylinder pressure of the engine, and an air-fuel ratio near the ignition plug 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. And an injection pressure control means for controlling the fuel injection pressure in the fuel injection valve based on the air-fuel ratio immediately before ignition calculated by the air-fuel ratio calculation means. Direct injection type spark ignition engine. 2. A required injection amount calculation 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 injection amount calculation means. An injection time calculating means for calculating the fuel injection pressure based on the fuel injection pressure controlled by the injection pressure control means; and a fuel injection pressure calculated by the injection time calculating means under the fuel injection pressure controlled by the injection pressure control means at a predetermined injection timing. 2. A direct injection spark ignition engine according to claim 1, further comprising: injection control means for controlling the opening of the fuel injection valve for a predetermined injection time.