JP2803371B2 - Idling control system for in-cylinder injection internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idling control apparatus for a direct injection internal combustion engine.

[0002]

2. Description of the Related Art A fuel injection valve for injecting fuel into a combustion chamber is provided, and fuel injected from the fuel injection valve is burned under excess air at the time of engine idling operation. The fuel injection amount is a function of the engine speed and is increased as the engine speed decreases, and the engine idling speed is controlled to the target speed based on the change in the fuel injection amount resulting from the change in the engine speed. 2. Description of the Related Art A direct injection internal combustion engine is known (see Japanese Patent Application Laid-Open No. 2-169834). In this internal combustion engine, when the engine idling speed is higher than the target speed, the fuel injection amount is reduced, so that the idling speed is reduced. When the idling speed is lower than the target speed, the fuel injection amount is increased. As a result, the idling speed increases, and thus the idling speed is automatically controlled to the target speed.

In the internal combustion engine in which the injected fuel is burned under excess air during the idling operation of the engine, no throttle valve is provided in the intake passage, or a throttle valve is provided in the intake passage. Even if the throttle valve is operated, the throttle valve cannot be closed to the idling opening of the premixed internal combustion engine even during idling operation in order to make the air in the combustion chamber excessive.
As described above, when the throttle valve is not provided in the intake passage, or even if the throttle valve is provided in the intake passage, the throttle valve is closed to the idling opening degree in the premixed internal combustion engine during idling operation. If not, the intake air amount Q supplied into the engine cylinder per unit time during idling operation increases in proportion to the increase in the engine speed N. Therefore, the intake air amount Q / N supplied to the engine cylinder per cycle is substantially constant regardless of the engine speed N.

Accordingly, in an internal combustion engine in which the injected fuel is burned under an excess of air during idling operation, the idling operation is performed while the intake air amount Q / N supplied to the engine cylinder is maintained substantially constant during idling operation. When the rotation speed becomes higher than the target rotation speed, the fuel injection amount is decreased, and when the idling rotation speed becomes lower than the target rotation speed, the fuel injection amount is increased.
In this case, if there is excess air in the combustion chamber, the amount of air contributing to combustion increases in proportion to the increase in the fuel injection amount when the fuel injection amount increases, and the amount of air in the engine cylinder increases when the fuel injection amount increases or decreases. The conventional general idea is that even if the intake air amount Q / N supplied to the fuel cell is changed, excess air is merely increased or decreased and combustion is not affected at all. Therefore, conventionally, in an internal combustion engine in which the injected fuel is burned under excess air during idling operation, the amount of intake air Q / N supplied to the engine cylinder is not controlled in order to control the idling speed. It is common.

[0005]

However, in fact, the amount of air mixed with the injected fuel does not increase in proportion to the increase in the fuel injection amount even though the fuel injection amount increases. Therefore, if the fuel injection amount increases, the air-fuel mixture in the combustion chamber becomes excessively rich, and if the fuel injection amount decreases, the air-fuel mixture in the combustion chamber becomes lean, and good combustion cannot be obtained in any case. In this case, in order to prevent the mixture in the combustion chamber from becoming too rich, the air density in the combustion chamber may be increased,
For this purpose, the intake air amount Q supplied into the engine cylinder
/ N should be increased. On the other hand, in order to prevent the air-fuel mixture in the combustion chamber from becoming too thin, the intake air amount Q / N supplied to the engine cylinder should be reduced.

In a premixed internal combustion engine, both the fuel amount and the intake air amount are controlled to control the idling rotational speed to the target rotational speed. Although it seems natural to control it, it is considered that it is meaningless to control the amount of intake air in a cylinder injection type internal combustion engine that burns injected fuel under excess air as described above. As described above, the concept of controlling the intake air amount in the direct injection internal combustion engine can be said to be a completely new concept.

[0007]

According to the present invention, in order to ensure good combustion regardless of the fuel injection amount during idling operation of a direct injection internal combustion engine, according to the present invention, fuel is injected into a combustion chamber. The fuel injected from the fuel injection valve is burned under excessive air during the engine idling operation, and the fuel injection amount during the engine idling operation is a function of the engine speed and the engine speed is increased. In a direct injection internal combustion engine in which the engine idling speed is controlled to a target speed based on a change in the fuel injection amount resulting from a change in the engine speed, the fuel is supplied to the engine cylinder. Equipped with an intake air amount control device for controlling the amount of intake air to be supplied to the engine cylinder as the engine speed decreases during engine idling operation. So that allowed to increase the amount of intake air.

[0008]

The fuel injection amount increases as the engine speed decreases, and the amount of intake air supplied into the engine cylinder increases.

[0009]

1 to 4 show a case where the present invention is applied to a spark ignition type two-cycle in-cylinder injection engine. 2 and 4
1, 1 is a cylinder block, 2 is a piston reciprocating in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, 4 is a space between the inner wall surface 3a of the cylinder head 3 and the top surface of the piston 2. Are shown, respectively. A concave groove 5 is formed on the cylinder head inner wall surface 3a, and a pair of air supply valves 6 are arranged on the cylinder head inner wall surface portion 3b that forms the bottom wall surface of the concave groove 5. On the other hand, the cylinder head inner wall surface portion 3c excluding the concave groove 5 is substantially flat and inclined.
A pair of exhaust valves 7 are arranged on c. The cylinder head inner wall surface portion 3b and the cylinder head inner wall surface portion 3c
Are connected to each other via a peripheral wall 8 of the first embodiment.

The peripheral wall 8 of the concave groove is located between the pair of mask walls 8a, which are arranged very close to the peripheral edge of the air supply valve 6 and extend in an arc along the peripheral edge of the air supply valve 6, and the air supply valve 6. And a pair of fresh air guide walls 8c located between the supply wall 6 and the peripheral wall of the cylinder head inner wall surface 3a. Each mask wall 8a extends toward the combustion chamber 4 below the intake valve 6 at the maximum lift position, so that the opening between the peripheral portion of the intake valve 6 located on the exhaust valve 7 side and the valve seat 9 is formed. The air supply valve 6 is closed by the mask wall 8a throughout the opening period of the air supply valve 6.

The fresh air guide walls 8b and 8c are located on substantially the same plane.
b and 8c extend substantially parallel to a line connecting the centers of the two supply valves 6. The ignition plug 10 is disposed on the cylinder head inner wall surface portion 3c so as to be located at the center of the cylinder head inner wall surface 3a. On the other hand, the exhaust valve 7
There is no mask wall covering the opening between the valve seat 11 and
Therefore, when the exhaust valve 7 opens, the entire opening formed between the exhaust valve 7 and the valve seat 11 opens into the combustion chamber 4.

An air supply port 12 is formed in the cylinder head 3 for the air supply valve 6, and an exhaust port is formed for the exhaust valve 7.
13 is formed. On the other hand, a fuel injection valve 14 is arranged at the peripheral portion of the cylinder head inner wall surface 3 a between the two supply valves 6, and fuel is injected from the fuel injection valve 14 into the combustion chamber 4.

As shown in FIGS. 2 and 3, a recessed groove 15 is formed on the top surface of the piston 2 from below the spark plug 10 to below the tip of the fuel injection valve 14. In the embodiment shown in FIGS. 2 and 3, the groove 15 has a substantially spherical shape which is symmetrical with respect to a vertical plane KK including the ignition plug 10 and the fuel injection valve 14. A groove 15 is formed in the center of the top surface of the piston 2.
A concave portion 16 having a spherical shape with a smaller radius of curvature is formed. This recess 16 is also formed on a vertical plane KK,
The recess 16 is open above the concave inner wall surface of the groove 15. As shown in FIG. 2, when the piston 2 reaches the top dead center, the spark plug 10 enters the recess 16. On the other hand, the top surface portion 2a of the piston 2 opposite to the concave groove 15 with respect to the concave portion 16 is formed of an inclined substantially flat surface, and when the piston 2 reaches the top dead center as shown in FIG. A squish area 17 is formed between 3c and the piston top surface portion 2a.

As shown in FIG. 5, shown in FIGS.
In the embodiment, the exhaust valve 7 opens before the air supply valve 6 and the exhaust valve 7 is opened.
The valve 7 closes before the air supply valve 6. Also, in FIG.
I ₁, I_Two, I_ThreeIndicates the fuel injection timing.

Referring to FIG. 1, an air supply port 12 of each cylinder is provided.
Is connected to a surge tank 19 via a branch pipe 18, and the surge tank 19 is connected to an air cleaner (not shown) via an air supply duct 20 and an air flow meter 21. Air supply duct 20
Inside, a mechanical supercharger 22 driven by an engine is arranged. A bypass passage 23 that connects the intake duct 20 upstream of the mechanical supercharger 22 and the intake duct 20 downstream of the mechanical supercharger 22 is connected to the intake duct 20. A bypass control valve 24 for controlling the amount of flowing air is provided. The bypass control valve 24 is driven by, for example, a step motor, and the step motor is controlled by an output signal of the electronic control unit 30.

The electronic control unit 30 is composed of a digital computer, and a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port
35 and an output port 36. Air flow meter 21
Generates an output voltage proportional to the amount of intake air, and this output voltage is input to an input port 35 via an AD converter 37.
Further, a load sensor 26 and an idle switch 27 are connected to the accelerator pedal 25. The load sensor 26 generates an output voltage proportional to the amount of depression of the accelerator pedal 25, and this output voltage is input to the input port 35 via the AD converter 38. On the other hand, the idle switch 27 is turned on when the accelerator pedal 25 is not depressed, and the output signal of the idle switch 27 is input to the input port 35. Further, the input port 35 is connected to a rotation speed sensor 28 for generating an output pulse indicating the engine speed and a vehicle speed sensor 29 for generating an output pulse indicating the vehicle speed. The CPU 34 calculates the engine speed based on the output pulse of the speed sensor 28,
The vehicle speed is calculated based on the output pulse of the vehicle speed sensor 29. On the other hand, the output port 36 is connected to the fuel injection valve 14 and the bypass control valve 24 via corresponding drive circuits 39 and 40, respectively.

In the embodiment shown in FIG. 1, the amount of intake air supplied into the engine cylinder is controlled by a bypass control valve 24. That is, when the bypass control valve 24 is opened, a part of the intake air discharged from the mechanical supercharger 22 into the intake duct 20 downstream of the mechanical supercharger 22 passes through the bypass passage 23 to the mechanical supercharger. The amount of intake air returned to the intake duct 20 upstream of the supercharger 22 and thus supplied to the engine cylinder is controlled by a mechanical supercharger.
It is reduced by the amount returned into the intake duct 20 upstream of 22.
Therefore, as the opening of the bypass control valve 24 increases, the amount of intake air supplied into the engine cylinder decreases.

FIG. 6 shows the relationship between the target opening S of the bypass control valve 24 and the depression amount L of the accelerator pedal 25 at a certain engine speed. As shown in FIG. 6, when the depression amount L of the accelerator pedal 25 decreases, that is, when the required load of the engine decreases, the target opening S of the bypass control valve 24 increases, and the amount of intake air supplied to the engine cylinder decreases. It turns out that you can be forced.

Next, the operation during the engine idling operation will be described with reference to FIGS. When the air supply valve 6 and the exhaust valve 7 are opened as shown in FIG.
The air flows into the combustion chamber 4 via At this time, since the opening of the air supply valve 6 on the side of the exhaust valve 7 is covered by the mask wall 8a, air flows into the combustion chamber 4 from the opening of the air supply valve 6 on the side opposite to the mask wall 8a. This air descends along the inner wall surface of the cylinder bore below the air supply valve 6 as shown by the arrow W, then travels along the top surface of the piston 2 and rises along the inner wall surface of the cylinder bore below the exhaust valve 7, and Will flow in a loop in the combustion chamber 4. The burned gas in the combustion chamber 4 is discharged through the exhaust valve 7 by the air W flowing in the loop, and the air W flowing in the loop is further discharged.
As a result, a swirling flow X swirling in a vertical plane is generated in the combustion chamber 4. Next, when the piston 2 starts to rise after passing the bottom dead center BDC and the exhaust valve 7 closes, the fuel injection valve
Fuel injection from 14 is performed.

Takes place at the end of the compression stroke so that the fuel injected from the fuel injection valve 14 is basically represented by I ₁ in Figure 5 when [0020] lower the engine load including the idling operation in this embodiment of the present invention . The state of fuel injection at this time is shown in FIG. That is, at the end of the compression stroke, fuel is injected from the fuel injection valve 14 toward the concave inner wall surface of the groove 15 so that the injected fuel F collides obliquely with the concave inner wall surface of the groove 15 as shown in FIG. . As described above, when the injected fuel obliquely collides with the concave inner wall surface of the concave groove 15, the colliding fuel is vaporized along the concave inner wall surface of the concave groove 15 by inertia as shown by G in FIG. And then sent into the recess 16. At the time of engine low load operation, the injection amount is small, but at this time most of the injected fuel is carried below the spark plug 10, so that an ignitable mixture G is formed around the spark plug 10. That is, at the time of engine low load operation, the area around the air-fuel mixture G is filled with air and residual burned gas,
The air in the combustion chamber 4 is in an excessive state. As described above, even if the air in the combustion chamber 4 is in an excessive state, the air-fuel mixture is
Since the mixture does not spread over the entire interior and becomes an extremely lean mixture, and is concentrated in a part of the region inside the combustion chamber 4, that is, the inside of the combustion chamber 4 is stratified, so that good ignition and subsequent Good combustion will be obtained.

Further, as shown in FIG. 7, the swirling flow X generated in the combustion chamber 4 is attenuated as the piston 2 rises, and the turning radius gradually decreases while decreasing, and when the piston 2 approaches the top dead center, FIG. As shown in FIG. 5, a swirling flow X along the concave inner wall surface of the concave groove 16 is obtained. The injection fuel F is also given a downward force by the swirl flow X. Also,
When the piston 2 further approaches the top dead center, the arrow S in FIG.
As shown by, a squish flow spouts from the squish area 17, and this squish flow S also advances along the concave inner wall surface of the concave groove 15. Therefore, the squish flow S gives the injected fuel F a force directed downward of the ignition plug 10. Further, the fuel flowing along the concave inner wall surface of the concave groove 15 toward the lower side of the ignition plug 10 is vaporized by the swirl flow X and the squish flow S, and thus a sufficiently vaporized combustible mixture is formed around the ignition plug 10. Will come together. Thus, even during low engine load operation with a small injection amount, good ignition and subsequent good combustion can be obtained.

When a large amount of intake air is supplied into the combustion chamber 4 during low engine load operation with a small fuel injection amount, the swirl flow X becomes too strong and the air-fuel mixture diffuses throughout the combustion chamber 4. I will. Therefore, during low engine load operation, the combustion chamber 4
It is necessary to limit the amount of intake air supplied to the inside. In particular, in the case of a two-cycle internal combustion engine, if the amount of intake air is restricted, the ratio of the remaining burned gas in the combustion chamber 4 increases, and the generation of NOx is suppressed by the action of suppressing the combustion temperature by the remaining burned gas. Therefore, as shown in FIG. 6, when the depression amount L of the accelerator pedal 25 is small, the bypass control valve 24 is opened to limit the amount of intake air supplied into the combustion chamber 4. In addition, during low engine load operation, the fuel injection time TA
U is determined from the depression amount L of the accelerator pedal 25 and the engine speed N, and these relationships are stored in the ROM 32 in advance in the form of a map as shown in FIG. Therefore, when the engine is under a low load operation including the idling operation, the amount of depression L of the accelerator pedal 25 and the engine speed N are calculated from FIG.
The fuel injection time TAU is determined based on the relationship shown in FIG.

On the other hand, when the engine load is high, the fuel injection valve
Fuel injection from 14 exhaust valve 7 as shown by I ₃ in FIG. 5 was closed, or the exhaust valve 7 is started from just before the closing. The state of fuel injection at this time is shown in FIG. That is, at this time, as shown in FIG. 9, the fuel injection F is performed when the position of the piston 2 is low, so that the injected fuel F goes to the entire top surface of the piston 2. Therefore, the injected fuel F diffuses throughout the combustion chamber 4. Further, at this time, since the swirl flow X is generated in the combustion chamber 4, the diffusion action of the injected fuel F is promoted by the swirl flow, so that a uniform air-fuel mixture is formed in the combustion chamber 4. Become. Also,
When the engine load is high, the fuel injection time TAU is determined from the intake air amount Q / N supplied per cycle into the engine cylinder and the engine speed N, and these relationships are shown in FIG.
As shown in (1), it is stored in the ROM 32 in advance in the form of a map. Therefore, when the engine load is high, the air flow meter 21
The fuel injection time TAU is determined based on the relationship shown in FIG. 10B from the intake air amount Q per unit time and the engine speed N detected by the above.

As described above, during the low engine load operation including the idling operation, the fuel injection time TAU is determined based on the relationship shown in FIG. By the way, during idling operation, the depression amount L of the accelerator pedal 25 is zero, and therefore, during idling operation, the fuel injection time TA
U is a function of only the engine speed N. FIG. 11 shows the relationship between the fuel injection time TAU and the engine speed N during idling operation. As can be seen from FIG. 11, during idling operation, the fuel injection time TAU increases exponentially as the engine speed N decreases. In FIG. 11, N ₀ indicates a target idling speed, and the target idling speed N ₀ is, for example, 600 rpm.

That is, the idling rotational speed is determined comprehensively by the fuel injection time TAU, the fuel injection timing, the opening of the bypass control valve 14, and the like. In the embodiment according to the present invention, the fuel injection time TAU and the opening degree of the bypass control valve 14 when the idling rotational speed reaches the target rotational speed N ₀ are obtained in advance by experiments, and the values obtained by the experiments are shown in FIG. It is stored in the ROM 32 in advance as shown in FIG. Therefore, if the fuel injection time TAU is set to TAU ₀ in FIG. 11 during the idling operation, the engine speed N basically becomes equal to the target idling speed N
It becomes ₀ . In this case, for some reason, the engine speed N becomes N
₀ engine speed N and the fuel injection time TAU increases if rises lower than while the engine speed since the engine rotational speed N for some reason the fuel injection time TAU decreases the higher than N ₀ N And the engine speed N is maintained at the target idling speed N ₀ .

If the opening of the bypass control valve 24 is fixed during idling operation, the intake air amount Q per unit time passing through the air flow meter 21 increases as the engine speed N increases, and at this time, the engine cylinder The intake air amount Q / N supplied per cycle is substantially constant irrespective of the idling speed. That is, the combustion chamber 4
The density of the intake air in the inside is almost constant irrespective of the idling speed. However, the region in which the fuel diffuses during idling operation, that is, the volume occupied by the air-fuel mixture G in FIG. 8 does not increase in proportion to the increase in the fuel injection amount. Therefore, when the density of the intake air in the combustion chamber 4 is kept constant irrespective of the idling rotational speed, the idling rotational speed becomes lower than the target rotational speed N ₀ and the fuel injection time TAU is increased. next mixture G is rich, the air-fuel mixture G the idling speed is higher than the target rotational speed N ₀ the fuel injection time TAU is made to decrease becomes lean. When the mixture G becomes excessively rich, not only a large amount of unburned HC and CO is generated, but also the combustion is deteriorated, so that the output torque of the engine is not sufficiently increased. There is a problem that the rotation cannot be returned immediately to the rotation speed N ₀ . On the other hand, if the air-fuel mixture becomes too thin, the risk of misfiring increases. If misfiring occurs, a problem arises in that a large amount of HC is discharged from the combustion chamber 4. In particular, in the case of a two-stroke internal combustion engine, when the idling speed becomes higher than the target speed N _{0 and} the degree of excess air increases, the proportion of the remaining burned gas in the combustion chamber 4 decreases, thus generating NOx. Cause problems.

[0027] Therefore exponentially as time in the intake air quantity Q / N and engine speed N which is supplied per cycle into the engine cylinder as shown by the solid line R ₁ in FIG. 12 idling decreases in the embodiment according to the present invention We are trying to increase it. As described above, when the intake air amount Q / N supplied per cycle to the engine cylinder is increased as the engine speed N decreases, the concentration of the air-fuel mixture G becomes substantially constant irrespective of the idling speed. An optimum mixture G is formed irrespective of the rotational speed, so that a good ignition and a subsequent good combustion are obtained irrespective of the idling rotational speed. Therefore unburned HC, along with the generation of CO can be suppressed can prevent the occurrence of misfire, moreover engine speed N target speed N ₀
When the engine speed drops, the engine output is immediately increased, so that the engine speed N can be promptly returned to the target speed N ₀ . Further, even if the idling rotational speed becomes higher than the target rotational speed N ₀ , the degree of excess air does not increase.
x can be prevented from occurring.

In the embodiment according to the present invention, the intake air amount Q / N during idling operation is controlled by the bypass control valve 24.
This is performed by controlling the opening degree. The solid line K in FIG.
Reference numeral ₁ denotes a relationship between the target opening S of the bypass control valve 24 and the engine speed N during the idling operation, and this relationship is stored in the ROM 32 in advance. Bypass control valve during idling operation as can be seen from the solid line K ₁ in FIG. 13
The target opening S of 24 increases exponentially as the engine speed N increases. If the opening degree of the bypass control valve 24 increases, the intake air amount Q / N decreases. Therefore, as the engine speed N increases, the intake air amount Q / N decreases.

Next, the control of the fuel injection time TAU and the control of the bypass control valve 24 will be described with reference to the main routine shown in FIG. Referring to FIG. 14, first, at step 50, it is determined whether or not the idle switch 27 is ON, that is, whether or not the depression amount L of the accelerator pedal 25 is zero. When the idle switch 25 is ON, the routine proceeds to step 51, where it is determined based on the output signal of the vehicle speed sensor 29 whether the vehicle speed is lower than a fixed value, for example, 2 km / h. When the vehicle speed is lower than 2 km / h, the routine proceeds to step 52. That is, when the depression amount L of the accelerator pedal 25 is zero and the vehicle speed is 2 km / h or less, it is determined that the vehicle is idling, and the process proceeds to step 52.

The target opening S of the bypass control valve 24 is calculated based on the relationship shown by the solid line K ₁ in step 52 FIG. 13 on the engine speed N. Next, at step 53, the bypass control valve
The step motor of the bypass control valve 24 is driven so that the opening of the valve 24 reaches the target opening S. Then step 54
Then, the fuel injection time TAU is calculated from the relationship shown in FIG. 10A based on the engine speed N. Next, at step 55, the injection start timing is calculated from the data stored in the ROM 32 in advance, and the injection completion timing is calculated from the injection start timing and the injection time TAU. Next, at step 56, the data to start the injection at the injection start timing and the data to complete the injection at the injection completion timing are output to the output port 36, and the fuel injection is performed based on these data.

On the other hand, if it is determined in step 50 that the idle switch 27 is off, or if it is determined in step 51 that the vehicle speed is higher than 2 km / h, that is, if the vehicle is not idling, the routine proceeds to step 57. In step 57, from the relationship shown in FIG.
Although 24 target openings S are calculated, the target opening S shown in FIG. 6 is actually a function of the engine speed N. Next, at step 58, the step motor of the bypass control valve 24 is driven such that the opening of the bypass control valve 24 becomes the target opening S. Next, at step 59, the fuel injection time TAU is calculated from the relationship shown in FIG. Next, at step 60, the injection start timing is calculated from the data stored in the ROM 32 in advance, and the injection completion timing is calculated from the injection start timing and the injection time TAU. Next, at step 61, data to start the injection at the injection start timing and data to complete the injection at the injection completion timing are output to the output port 36, and the fuel injection is performed based on these data.

In FIG. 13, a broken line K ₂ shows another embodiment of the target opening S of the bypass control valve 24 during the idling operation. Engine like the target opening S indicated by the solid line K ₁ when this embodiment is between the N ₁ and N ₂ of the engine rotational speed N as shown in FIG. 13 around the target idling speed N ₀ As the rotational speed N increases, the target opening S increases exponentially. That is, as the engine speed N increases, the intake air amount Q / N supplied to the engine cylinder per cycle becomes equal to the broken line R _{2 in} FIG.
Is reduced as shown by. On the other hand, when the engine speed N during idling operation becomes higher than N ₂ , the target opening S of the bypass control valve 24 becomes the solid line K
Are made to increase than the target opening degree S shown in _1, therefore the intake air quantity Q, as is indicated by the dashed line R ₂ in FIG. 12 in this case
/ N is used to lower than the intake air amount Q / N shown by the solid line R _1. Further, when the engine speed N at the time of idling operation is lower than N ₁ is the bypass control valve 24
Target opening S is being made to increase than the target opening degree S indicated by a solid line K _1, therefore the intake air amount shown in intake air quantity Q / N is solid R ₁ as is shown by the dashed line R ₂ in FIG. 12 in this case of the It is reduced from Q / N. Further, the injection timing is advanced as indicated by I ₂ in FIG. 5 when the engine speed N at the time of idling operation is lower than N _1. Therefore, at this time, as shown in FIG. 9, the fuel F is injected toward the entire top surface of the piston 2, and thus a uniform mixture is formed in the combustion chamber 4.

When the engine speed N is N during idling operation_Two
If it is higher than the fuel injection time T as can be seen from FIG.
The AU is much shorter, so the fuel injection amount is
Less. When the fuel injection amount decreases, the volume occupied by the mixture G
At this time, a strong swirling flow X or strong
When a strong turbulence is generated in the combustion chamber 4, the mixture G
As a result, an air-fuel mixture G having an optimum concentration is dispersed around the spark plug 10.
It is difficult to collect them. So in this example
During idling operation, the engine speed N becomes N _Twothan
When it becomes higher, the broken line K in FIG._TwoAs shown in the figure, the intake air amount Q /
Decrease N, thereby reducing swirl X or turbulence
Thus, the mixture G is collected around the ignition plug 10.
In a two-cycle internal combustion engine, the intake air
Decreasing the air volume Q / N reduces the degree of excess air.
Therefore, generation of NOx is prevented.

On the other hand, when the engine speed N during the idling operation decreases, the fuel injection time TAU increases exponentially as shown in FIG.
_If it falls below ₁ , the fuel injection amount will increase considerably. At this time, if all the fuel is injected into the groove 15, the air-fuel mixture becomes extremely rich, or the fuel
There is a risk of adhering to the inner wall surface of the vehicle. I in Figure 5 injection timing when therefore the engine speed N becomes lower than N ₁
The time to form a homogeneous mixture in earlier as indicated by ₂ not the homogeneous air-fuel mixture and lean, as shown by the broken line R ₂ in FIG. 12 so that darker Rather, the intake air quantity Q / N
Is to be reduced.

Although the present invention has been described for the case where the present invention is applied to a direct injection two-stroke engine, the present invention can also be applied to a direct injection four-cycle engine including a diesel engine.

[0036]

As described above, even if the engine speed fluctuates during idling operation, good combustion can be obtained regardless of the engine speed, so that a large amount of unburned HC and CO can be prevented from being generated. Even if the number of revolutions is reduced, good combustion is obtained, so that the engine output torque is immediately increased, so that the occurrence of engine stall can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall view of a direct injection two-stroke internal combustion engine.

FIG. 2 is a side sectional view of a two-cycle internal combustion engine.

FIG. 3 is a plan view of a piston top surface.

FIG. 4 is a bottom view of the inner wall surface of the cylinder head.

FIG. 5 is a diagram showing a valve opening timing and a fuel injection timing of a supply / exhaust valve.

FIG. 6 is a diagram showing a target opening of a bypass control valve.

FIG. 7 is a side sectional view of the two-stroke internal combustion engine showing a state where the supply / exhaust valve is opened.

FIG. 8 is a side cross-sectional view of the two-stroke internal combustion engine showing fuel injection.

FIG. 9 is a side cross-sectional view of the two-stroke internal combustion engine showing fuel injection.

FIG. 10 is a diagram illustrating a fuel injection time.

FIG. 11 is a diagram showing a fuel injection time during an idling operation.

FIG. 12 is a diagram illustrating an intake air amount supplied per cycle to an engine cylinder during an idling operation.

FIG. 13 is a diagram showing a target opening degree of a bypass control valve.

FIG. 14 is a flowchart of a main routine.

[Description of Signs] 14 ... Fuel injection valve 22 ... Mechanical supercharger 23 ... Bypass passage 24 ... Bypass control valve

────────────────────────────────────────────────── ⁶ Continuation of the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301L (56) References JP-A-62-191643 (JP, A) JP-A-2-40052 (JP, A) JP-A-62-28641 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00 395

Claims (1)

(57) [Claims] A fuel injection valve for injecting fuel into a combustion chamber is provided, and fuel injected from the fuel injection valve is burned under excessive air during an engine idling operation. The fuel injection amount is a function of the engine speed and is increased as the engine speed decreases, and the engine idling speed is controlled to the target speed based on the change in the fuel injection amount resulting from the change in the engine speed. An in-cylinder injection type internal combustion engine includes an intake air amount control device for controlling an intake air amount supplied to an engine cylinder, and is supplied to the engine cylinder as the engine speed decreases during an engine idling operation. Control device for an in-cylinder injection type internal combustion engine which increases an intake air amount.