JPH06257432A - Fuel supply system for internal combustion engine - Google Patents

Abstract

PURPOSE:To stratify a mixture by specifying the injection direction and injection timing of fuel. CONSTITUTION:In the fuel supply system of an internal combustion engine, which is having constitution in which two air intake ports are opened in a line mutually to a combustion chamber wall 9 and a longitudinal direction spiral flow is caused in a cylinder 2, and in which a spark plug 8 is arranged in the nearly middle of a combustion chamber 11 and a fuel injection valve 4 is arranged on the upstream side from the branch point of each air intake port; the fuel injection direction of the fuel injection valve 4 is set in the upper part region, on the inner side nipped by the valve stem 16 of each air intake valve 1 and near to the spark plug 8, and fuel injection timing is set in the first half of the intake stroke of air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved fuel supply system for an internal combustion engine.

[0002]

2. Description of the Related Art As a method for obtaining stable combustion even with a lean air-fuel mixture, an appropriate air flow is generated in a combustion chamber,
Stratification of the air-fuel mixture that makes the air-fuel ratio near the spark plug richer than the other is effective.

As a fuel supply device for stratifying an air-fuel mixture, there is a conventional fuel supply device as shown in, for example, FIG. 11 (see JP-A-61-237881).

Explaining this, the combustion chamber 11 has two
The intake ports 6 are opened side by side, and the combustion chamber 11
Is an internal combustion engine in which a spark plug 8 is disposed substantially at the center of the intake port 6 and a fuel injection valve 4 is disposed upstream of a branch point of each intake port 6, and the fuel injected from the fuel injection valve 4 is 6
The valve stem 1 of each intake valve 1 when reaching the open end of the
The target area 47 for spraying, which is shown by hatching in the figure set inside the area sandwiched by 6 is reached. This aims to stratify the air-fuel mixture that collects most of the injected fuel in the vicinity of the spark plug 8.

[0005]

However, in such a conventional fuel supply device for an internal combustion engine, the spray aiming region 47 is set over the entire inner region sandwiched by the valve stems 16 of the intake valves 1. Therefore, if a vertical swirl flow is to be generated in the combustion chamber 11 in order to improve combustion, the fuel supplied to the upper part of the spray target area 47 rides on the main flow of the swirl flow to form a rich mixture. Although it is possible to swirl in the cylinder as a lump, the fuel supplied to the lower part of the spray target area 47 cannot successfully ride on the main flow of the swirl flow,
It spreads widely in the cylinder. Further, there is a case in which the rich air-fuel mixture that has flown into the main flow of the swirl flow collides with the fuel that could not successfully get into the main flow of the swirl flow, and this rich air-fuel mixture collapses and diffuses into the cylinder. For this reason, it is difficult to collect the rich air-fuel mixture in the vicinity of the spark plug which reaches the ignition timing, and there is a problem that the combustion becomes unstable particularly in the case of performing lean combustion.

In view of the above problems, the present invention aims to stratify the air-fuel mixture by specifying the fuel injection direction and the fuel injection timing.

[0007]

The invention according to claim 1 is
Two intake ports that open side by side on a combustion chamber wall defined by the cylinder head, intake valves respectively arranged at the intake ports, means for generating a vertical swirl flow in the cylinder, and combustion In an internal combustion engine including a spark plug arranged substantially in the center of a chamber and a fuel injection valve arranged upstream of a branch point of each intake port, the fuel injection direction of the fuel injection valve is set to the valve of each intake valve. The fuel injection timing is set in the first half of the intake stroke by setting it in the upper region that is inside the stem and close to the spark plug.

According to the second aspect of the present invention, two intake ports are formed in the combustion chamber wall defined by the cylinder head so as to open side by side with each other, an intake valve provided in each intake port, and a vertical cylinder in the cylinder. For injecting fuel in an internal combustion engine including means for generating a swirling flow in a direction, a spark plug arranged substantially in the center of the combustion chamber, and a fuel injection valve arranged upstream of a branch point of each intake port. The fuel injection direction of the valve is set to the inner region sandwiched by the valve stems of the intake valves and to the lower region close to the cylinder, and the fuel injection timing is set to the latter half of the intake stroke.

According to the third aspect of the present invention, the wall surface of the partition wall that partitions each intake port is formed in a flat shape.

[0010]

According to the first aspect of the present invention, in order to generate a vertical swirling flow in the cylinder, the intake air sucked into the combustion chamber mainly passes through the upper region of the intake valve, which is closer to the spark plug than the valve stem. To do. On the other hand, the injection direction of the fuel injection valve is set to the upper region. However, most of the fuel injected in the first half of the intake stroke swirls in the cylinder along the vertical swirling flow generated in the cylinder as a rich air-fuel mixture. At this time, since the injection direction of the fuel injection valve is set along the main flow of intake air, most of the injected fuel swirls in the cylinder as a rich air-fuel mixture without widely spreading in the cylinder. The injection direction of the fuel injection valve is set to the inside of the valve stem of each intake valve, and in combination with the ignition timing near the compression top dead center, the fuel is vertically swirled in the cylinder. The air-fuel mixture can reach the vicinity of the spark plug, the stratification of the air-fuel mixture that makes the air-fuel ratio in the vicinity of the spark plug richer than the other is obtained, and stable lean combustion can be realized.

According to the second aspect of the present invention, the intake air taken into the combustion chamber mainly passes through the upper region of the intake valve closer to the spark plug than the valve stem of each intake valve, and causes a vertical swirling flow in the cylinder. . On the other hand, the injection direction of the fuel injection valve is set to a lower region closer to the cylinder than the valve stem of each intake valve, and its injection timing is set to the latter half of the intake stroke. However, most of the fuel injected from the fuel injection valve slowly flows into the cylinder from the lower region as a rich air-fuel mixture, and joins the swirling flow already swirling in the cylinder with good timing. When the ignition timing is reached near the compression top dead center, the injection direction of the fuel injection valve is set to the inner side sandwiched between the valve stems of the intake valves, and the rich air-fuel mixture is discharged from the spark plug. It is possible to reach the vicinity, and stratification of the air-fuel mixture that makes the air-fuel ratio near the spark plug richer than others can be obtained, and stable lean combustion can be realized. At this time, since the rich air-fuel mixture can be merged with the swirling flow at a timing immediately before ignition, it is possible to prevent the injected fuel from widely diffusing into the cylinder, and the swirling flow generated in the cylinder can be suppressed. Even if the power is relatively weakened, it is possible to collect a large amount of fuel in the vicinity of the spark plug which reaches the ignition timing.

According to the third aspect of the present invention, by forming the wall surface of the partition wall flat, it is possible to prevent the fuel spray injected from the fuel injection valve from adhering to the wall surface of the partition wall and forming a wall flow. It is possible to expand the degree of freedom in setting the fuel injection valve in the fuel injection direction.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the intake passage 10 has two intake ports 6 communicating with the combustion chamber 11 of one cylinder.
And the intake valve 1 is arranged in each intake port 6.

The combustion chamber wall 9 is formed on the cylinder head so as to be inclined in a pent roof type. Each intake port 6 is opened side by side with the combustion chamber wall 9, and an exhaust port (not shown) is opened on the side facing the opening of each intake port 6. Combustion chamber 1
An ignition plug 8 is arranged at the center of 1. In addition, 17 in the figure
Is a piston.

The intake ports 6 are straight and symmetrically formed. As a means for generating a vertical swirling flow in the cylinder 2, a tumble control valve 5 is provided at the upstream end of each straight intake port 6. The tumble control valve 5 has an intake passage 10
Notch 5 that is offset from the center of the flow path and opens
a is formed. As shown in the figure, when the tumble control valve 5 is closed so that its peripheral edge is brought into contact with the inner wall surface of the intake passage 10, the intake air passes through the notches 5a and the intake flow velocity is increased in the upper region of each intake port 6. As shown by the arrow in FIG. 2, the vertical swirl flow generated in the cylinder 2 is strengthened.

The tumble control valve 5 has a valve shaft 13 connected to an actuator (not shown). The actuator control device closes the tumble control valve 5 when the engine load is low, and opens the tumble control valve 5 when the engine load is medium and high.

As a means for generating a vertical swirling flow in the cylinder 2, the axis of the intake valve 1 is made to substantially coincide with the inclination of the intake port 6, and the inclination of the memorial chamber 9E on the exhaust valve side is made to flow into the intake air. It is also possible to set so as to be substantially parallel to the direction.

A fuel injection valve 4 is provided in the middle of the intake passage 10. The fuel injection valve 4 is arranged upstream of the branch point 14 of each air port 6 and above the tumble control valve 5.

The fuel injection valve 4 has two injection holes directed to each intake port 6, and the fuel spray injected from each injection hole reaches the opening of each intake port 6 to the combustion chamber 11. The target area 7 is located inside the valve stem 16 of each intake valve 1 and is set to an upper area closer to the spark plug 8 than the valve stem 16 of each intake valve 1.

More specifically, the spray target area 7 is located inside the center line of each valve stem 16 and is located closer to the spark plug 8 than two virtual planes each containing the center line of each valve stem 16. Near side (upper area)
The spray angle at which the fuel spray exiting each injection hole diffuses is set to about 8 °. As described above, when the spray angle is narrowed, atomization of the fuel tends to be deteriorated, but in order to reduce the particle size of the fuel to 50 μm or less, the assist air (pressurized air) is supplied from the fuel injection valve 4 together with the fuel. It is also possible to inject.

As shown in FIG. 3, the fuel supply period from the fuel injection valve 4 is set in the first half of the intake stroke in which each intake valve 1 opens.

Next, the operation will be described.

When the tumble control valve 5 is closed in order to generate a vertical swirling flow in the cylinder 2, most of the intake air passes through the notches 5a and is sucked into the combustion chamber 11 of each intake port 6. The intake air mainly passes through the spray aiming area 7 (upper area) which is closer to the spark plug 8 than the valve stem 16 of each intake valve 1. On the other hand, the injection direction of the fuel injection valve 4 is set in such an upper region.

Here, as shown in FIG. 4, each spray target area 7 is a gap 18 formed between the opening edge portion 17 of the intake port 6 and the umbrella portion 15 of the intake valve 1 in the valve open state. That is, most of the fuel injected by the fuel injection valve 4 is sucked into the combustion chamber 11 through the gaps 18 of the intake port 6 without colliding with the intake valve 1.

However, most of the fuel injected in the first half of the intake stroke swirls in the cylinder 2 along the vertical swirling flow generated in the cylinder 2 as a rich air-fuel mixture. At this time, since the injection direction of the fuel injection valve 4 is set substantially along the main flow of the intake air, most of the injected fuel does not diffuse into the cylinder and the cylinder 2 forms a rich air-fuel mixture.
You can turn inside. Here, as shown in FIG. 5, since the injection direction of the fuel injection valve 4 is set to the inside sandwiched by the valve stems 16 of the intake valves 1, a rich mixture lump swirls in the central region of the cylinder 2. A swirling flow of the lean air-fuel mixture is generated in a lateral region of the cylinder 2. The swirling flow in which the rich air-fuel mixture swirls and the swirling flow of the lean air-fuel mixture hardly mix with each other and flow independently.

On the other hand, by adjusting the shape of the intake port 6 and the shape of the tumble control valve 5, the rich air-fuel mixture is adjusted so as to store in the cylinder 2 approximately once or twice before the compression top dead center. , The rich air-fuel mixture can reach the vicinity of the spark plug 8 at approximately the ignition timing.
The air-fuel ratio in the vicinity of can be made richer than the others. As a result, the fuel consumption is reduced, the sieve can perform a large amount of exhaust gas recirculation (EGR), and the emission of nitrogen oxides can be reduced.

Next, another embodiment shown in FIGS. 6 to 9 will be described. The parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals.

In the fuel injection valve 4, the spray target area 27 where the fuel spray injected from each injection hole reaches the opening of each intake port 6 with respect to the combustion chamber 11 is sandwiched by the valve stem 16 of each intake valve 1. And located in the lower region closer to the cylinder 2 than the valve stem 16 of each intake valve 1.

That is, the spray target area 27 is located inside the center line of each valve stem 16, and is closer to the wall surface of the cylinder 2 than the two virtual surfaces including the center line of each valve stem 16 (lower part). The spray angle at which the fuel spray exiting each injection hole diffuses is set to about 8 °.

As shown in FIG. 8, the fuel supply period from the fuel injection valve 4 is set in the latter half of the intake stroke in which each intake valve 1 opens.

Next, the operation will be described.

When the tumble control valve 5 is closed, the intake air sucked into the combustion chamber 11 mainly passes through the upper region of the intake valve 1 closer to the spark plug 8 than the valve stem 16 of the intake valve 1, and is vertically introduced into the cylinder 2. Creates a swirling flow in any direction. On the other hand, the injection direction of the fuel injection valve 4 is set to the spray target area 27 (lower area) closer to the wall surface of the cylinder 2 than the valve stem 16 of each intake valve 1, and the injection timing is set to the latter half of the intake stroke. To be done.

However, most of the fuel injected from the fuel injection valve 4 does not ride on the main flow of the intake air and slowly flows into the cylinder 2 from the lower region as a rich air-fuel mixture, and has already swirled in the cylinder 2. It joins the swirling flow in time. Here, the target area 27 of each spray overlaps with the opening edge portion 17 of the intake port 6 and the umbrella portion 15 of the intake valve 1 in the open state, as shown in FIG. Most of the injected fuel collides with the umbrella portion 15 and is sucked laterally close to the wall surface of the cylinder 2 as shown in FIG. 7.

Along with the ignition timing approaching the compression top dead center, the injection direction of the fuel injection valve 4 is set inside the valve stem 16 of each intake valve 1,
The rich air-fuel mixture can reach the vicinity of the spark plug 8, and stratification of the air-fuel mixture that makes the air-fuel ratio near the spark plug 8 richer than others can be obtained, and stable lean combustion can be realized. .

At this time, since the rich air-fuel mixture can be merged into the swirling flow immediately before the ignition, the injected fuel can be suppressed from widely spreading in the cylinder 2,
Further, even if the power of the swirl flow generated in the cylinder 2 is relatively weakened, it is possible to collect a large amount of fuel in the vicinity of the spark plug 8 which reaches the ignition timing.

Next, in another embodiment shown in FIG. 10, the wall surface 20a of the partition wall 20 which separates each intake port 6 is formed in a flat shape.

The cross section of each intake port 6 is formed in a shape combining a semicircle and a rectangle, and the upper and lower corners 2 of each intake port 6 are formed.
0b is curved and formed in an arc shape.

In this case, by forming the wall surface 20a of the partition wall 20 in a flat shape, it is possible to prevent the fuel spray injected from the fuel injection valve 4 from adhering to the wall surface 20a and forming a wall flow. As a result, restrictions on the fuel injection direction of the fuel injection valve 4 are reduced, and the degree of freedom in setting the spray target area 7 and the spray target area 27 in the above-described embodiments can be expanded.

[0040]

According to the first aspect of the present invention, the two intake ports that open in parallel with each other in the combustion chamber wall defined by the cylinder head, the intake valves respectively disposed in the intake ports, and the cylinder. In an internal combustion engine provided with a means for generating a vertical swirl flow therein, an ignition plug arranged substantially in the center of the combustion chamber, and a fuel injection valve arranged upstream of a branch point of each intake port. Since the fuel injection direction of the fuel injection valve was set to the upper area inside the valve stem of each intake valve and close to the spark plug, and the fuel injection timing was set to the first half of the intake stroke, the fuel was injected from the fuel injection valve. Most of the fuel does not spread widely in the cylinder and swirls inside the cylinder as a rich mixture mass, effectively stratifying the mixture that makes the air-fuel ratio near the spark plug richer than the others, and stabilizes. Realizes lean combustion It is possible.

According to the second aspect of the present invention, the fuel injection direction of the fuel injection valve is set inside the valve stem of each intake valve and in the lower region close to the cylinder, and the fuel injection timing is set in the latter half of the intake stroke. Since the setting is made, the rich air-fuel mixture can be merged into the swirling flow immediately before the ignition, so that the injected fuel can be prevented from widely spreading in the cylinder, and the swirling flow generated in the cylinder can be suppressed. Even if the power is relatively weakened, it is possible to collect a large amount of fuel in the vicinity of the spark plug that is approaching the ignition timing, effectively stratifying the air-fuel mixture that makes the air-fuel ratio in the vicinity of the spark plug richer than others. Therefore, stable lean combustion can be realized.

According to the third aspect of the present invention, since the wall surface of the partition wall that separates the intake ports arranged side by side is formed in a flat shape, the fuel spray injected from the fuel injection valve adheres to the wall surface of the partition wall. It is possible to suppress the occurrence of a wall flow and expand the degree of freedom in setting the fuel injection valve in the fuel injection direction.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an engine showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the same engine.

FIG. 3 is a diagram similarly showing a fuel supply timing and an air intake period.

FIG. 4 is a perspective view showing a spray target area.

FIG. 5 is a diagram showing intake air flow in the cylinder.

FIG. 6 is a schematic plan view of an engine showing another embodiment.

FIG. 7 is a vertical sectional view of the engine.

FIG. 8 is a diagram similarly showing a fuel supply timing and an air intake period.

FIG. 9 is a perspective view showing a spray target area in the same manner.

FIG. 10 is a cross-sectional view of an engine showing another embodiment.

FIG. 11 is a schematic plan view of an engine showing a conventional example.

[Explanation of symbols]

 1 intake valve 2 cylinder 4 fuel injection valve 6 intake port 8 spark plug 9 combustion chamber wall 11 combustion chamber 16 valve stem 20 bulkhead

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location F02M 69/00 C 7825-3G 69/04 P 7825-3G (72) Inventor Minoru Imajo Kanagawa 2 Takaracho, Kanagawa-ku, Yokohama-shi Nissan Motor Co., Ltd.

Claims (3)

[Claims] 1. A combustion chamber wall defined by a cylinder head, two intake ports that open side by side with each other, intake valves respectively provided in the intake ports, and a vertical swirl flow in the cylinder. In the internal combustion engine, a spark plug arranged substantially in the center of the combustion chamber, and a fuel injection valve arranged upstream of the branch point of each intake port. A fuel supply system for an internal combustion engine, characterized in that the fuel injection timing is set in the upper region inside the valve stem of each intake valve and close to the spark plug, and the fuel injection timing is set in the first half of the intake stroke. 2. A combustion chamber wall defined by a cylinder head, two intake ports opening side by side with each other, intake valves respectively arranged at the intake ports, and a vertical swirling flow in the cylinder. In the internal combustion engine, a spark plug arranged substantially in the center of the combustion chamber, and a fuel injection valve arranged upstream of the branch point of each intake port. A fuel supply device for an internal combustion engine, characterized in that a fuel injection timing is set in a lower region inside the valve stem of each intake valve and close to a cylinder, and is set in a latter half of an intake stroke. 3. The fuel supply device for an internal combustion engine according to claim 1, wherein a wall surface of a partition wall that partitions each intake port is formed in a flat shape.