JPH10231729A - Intake device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rationalize a turning direction of intake having two layers generated to a cylinder so as to realize a stratified burning by separating an intake passage into a mixture passage provided with a fuel injection valve and an air regulating valve and an air passage by a partition, and forming a cross section area of the mixture passage larger than that of the air passage. SOLUTION: An intake passage 9 is separated into an air passage 7 and a mixture passage 8 provided with a fuel injection valve 5 and a butterfly type air regulating valve 10 by a partition 6. The cross section area of the mixture passage 8 is formed larger than that of the air passage 7 with a ratio of nearly 6:4, and thereby, speed component of air flow which flows from the air passage 7 to an outer periphery side of a cylinder 1 is improved properly in an operating condition in which the air regulating valve 10 is closed. It is thus possible to improved tumble component of intake turning flow generated to the cylinder 1, and it is also possible to suppress damping of energy of intake turning flow in association with that a piston achieves a top dead center so as to stratify mixture for collecting fuel in the vicinity of an ignition plug 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an intake device 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, stratification of an air-fuel mixture in which an intake swirling flow is generated in a cylinder to collect fuel near an ignition plug is effective.

As an intake device that generates an intake tumble according to operating conditions, for example, as shown in FIG.
There is one disclosed in Japanese Patent No. 321679.

To explain this, two intake ports for introducing intake air into the cylinder 20 have a central intake passage 31 having an opening near the center of the cylinder 30 and an opening near the outer periphery of the cylinder 30. It is divided into a side intake passage 32 and each.

[0005] The two intake valves 37 open and close at a predetermined timing synchronized with the rotation of the engine. A fuel injection nozzle 34 faces the central intake passage 31, and the air-fuel mixture is introduced from the central intake passage 31 near the center of the cylinder 30 with the opening of the intake valve 37, and near the outer periphery of the cylinder 30. Air is introduced from the side intake passage 32. This allows
In the cylinder 30, as shown by the arrow in the drawing, an intake tumble in which the two-layered intake air turns vertically is generated, and the ignition plug 3
The stratification of the air-fuel mixture for collecting fuel near 5 is achieved.

[0006]

However, in such a conventional intake system for an internal combustion engine, the cylinder 3
At 0, the intake tumble in which the intake air turns in the vertical direction is weakened when the piston 36 reaches near the top dead center, and the ignition plug 35
It is difficult to collect fuel near the area. For this reason, there has been a problem that stable stratified combustion is not performed, leading to misfire and deterioration of exhaust emission due to cycle fluctuation.

In a two-valve engine having a single intake valve and a single exhaust valve for one cylinder, the spark plug is provided eccentrically with respect to the cylinder. It is difficult to collect fuel near the area.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to realize stratified combustion in an intake device of an internal combustion engine by optimizing a turning direction of a two-layer intake air generated in a cylinder. And

[0009]

According to a first aspect of the present invention, there is provided an intake system for an internal combustion engine comprising: an intake passage for guiding intake air to one cylinder; and a single intake valve for opening and closing the intake passage in synchronization with engine rotation. An internal combustion engine having an exhaust passage for discharging exhaust from a cylinder, a single exhaust valve for opening and closing the exhaust passage in synchronization with engine rotation, and a spark plug facing the cylinder substantially opposite to the exhaust valve. A partition that divides the mixture passage into an air passage opening toward the center of the cylinder and an air passage opening toward the outer periphery of the cylinder, a fuel injection valve that supplies fuel to the mixture passage, and air that restricts the mixture passage according to the operation state. And a regulating valve, wherein the cross-sectional area of the mixture passage is formed larger than the cross-sectional area of the air passage.

According to a second aspect of the present invention, there is provided an intake system for an internal combustion engine.
In the invention described in claim 1, the ratio of the cross-sectional area of the mixture passage to the cross-sectional area of the air passage is set to approximately 6: 4.

According to a third aspect of the present invention, there is provided an intake system for an internal combustion engine.
3. The invention according to claim 1, wherein the center line of the air passage is farther away from the spark plug than the center line of the mixture passage, and the center line of the air passage is located below the center line of the mixture passage. It was arranged.

According to a fourth aspect of the present invention, there is provided an intake system for an internal combustion engine.
In the invention according to any one of claims 1 to 3,
The angle formed between the horizontal plane intersecting with the passage center line of the mixture passage and the line segment connecting the passage center line of the mixture passage and the center line of the air passage is set to about 45 degrees.

According to a fifth aspect of the present invention, there is provided an intake system for an internal combustion engine.
In the invention according to any one of claims 1 to 4,
At least a part of the air passage is disposed below the mixture passage.

According to a sixth aspect of the present invention, there is provided an intake system for an internal combustion engine.
In the invention according to any one of claims 1 to 5,
The mixture passage has a portion whose cross-sectional area increases from below to above, and the air passage has a portion whose cross-sectional area increases from above to below.

An intake device for an internal combustion engine according to claim 7 is
In the invention according to any one of claims 1 to 6,
The mixture passage has a portion in which the ratio of the cross-sectional area of the air passage to the cross-sectional area is constant and the maximum width in the lateral direction gradually increases from the upstream side to the downstream side.

The intake device for an internal combustion engine according to claim 8 is
In the invention according to any one of claims 1 to 7,
The mixture passage has a portion where the ratio of the cross-sectional area of the air passage to the cross-sectional area gradually decreases from the upstream side to the downstream side of the intake passage.

An intake device for an internal combustion engine according to claim 9 is
In the invention according to any one of claims 1 to 8,
The air regulating valve interposed in the mixture passage connected to the left and right banks of the V-type internal combustion engine is driven to open and close via a common shaft.

According to a tenth aspect of the present invention, in the intake system for an internal combustion engine according to any one of the first to ninth aspects, the air regulating valve is configured to close in a low speed and low load range.

According to an eleventh aspect of the present invention, there is provided an intake system for an internal combustion engine according to any one of the first to tenth aspects, further comprising a partition partitioning the intake passage into a mixture passage and an air passage. Is formed so as to face the back of the umbrella of the intake valve.

[0020]

In the intake system for an internal combustion engine according to the first aspect of the present invention, under the operating condition in which the air regulating valve is held at the closed position, most of the intake air flows into the cylinder through the air passage from the outer periphery thereof. . Fuel injected from the fuel injection valve passes through the mixture passage and is introduced near the center of the cylinder. In the cylinder, two-layered intake air composed of an air-fuel mixture guided from an air-fuel passage and an air-fuel mixture guided from an air passage is swirled to stratify the air-fuel mixture that collects fuel near the spark plug.

However, if the ratio of the swirl component or the tumble component of the intake swirling flow generated in the cylinder is not appropriate under the operating conditions in which the air regulating valve is held at the closed position,
As the piston reaches the top dead center, the power of the intake swirling flow is attenuated, and stratification of the air-fuel mixture that collects fuel near the spark plug is prevented.

According to the present invention, in order to cope with this, the cross-sectional area of the air-fuel mixture passage is formed to be larger than the cross-sectional area of the air passage. The velocity component of the incoming air flow can be increased appropriately.

Thus, by optimizing the power of the intake swirling flow generated in the cylinder, stratification of the air-fuel mixture for collecting fuel near the ignition plug is achieved, and stable combustion can be obtained even with a lean air-fuel mixture. As a result, it is possible to prevent misfire or deterioration of exhaust emission due to cycle fluctuation.

In the intake system for an internal combustion engine according to the second aspect, by setting the ratio of the cross-sectional area of the mixture passage to the cross-sectional area of the air passage to be 6: 4, the air conditioner can be closed in an operating state. Thus, the velocity component of the airflow flowing from the air passage toward the outer periphery of the cylinder can be appropriately increased.

In this way, by optimizing the power of the intake swirling flow generated in the cylinder, stratification of the air-fuel mixture for collecting fuel near the spark plug is achieved, and stable combustion can be obtained even with a lean air-fuel mixture.

According to a third aspect of the present invention, the center line of the air passage is farther away from the spark plug than the center line of the mixture passage, and the center line of the air passage is set at the center of the mixture passage. By placing it below the line,
In the operation state of closing the air regulating valve, the tumble component of the intake swirl flow generated in the cylinder is increased, and the power of the intake swirl flow is suppressed from being attenuated as the piston reaches the top dead center, A stratification of the air-fuel mixture for collecting fuel near the spark plug is achieved.

In the intake system for an internal combustion engine according to the fourth aspect, an angle formed by a horizontal plane intersecting the passage center line of the mixture passage with a line segment connecting the passage center line of the mixture passage and the center line of the air passage is about 45 degrees. In the operation state where the air regulating valve is closed, the tumble component of the intake swirl flow generated in the cylinder is appropriately increased, and as the piston reaches the top dead center, the intake swirl flow is reduced. Attenuation of the power is suppressed, and stratification of the air-fuel mixture for collecting fuel near the spark plug is achieved.

In the intake system for an internal combustion engine according to the fifth aspect, at least a part of the air passage is located below the mixture passage, so that the air conditioner is generated in the cylinder in an operation state in which the air regulating valve is closed. The tumble component of the intake swirl flow is increased, and the power of the intake swirl flow is suppressed from being attenuated as the piston reaches the top dead center, whereby stratification of the air-fuel mixture that collects fuel near the spark plug is achieved.

According to a sixth aspect of the present invention, the air-fuel mixture passage has a portion whose cross-sectional area increases from below to above, and the air passage has a portion whose cross-sectional area increases from above to below. By having this, the tumble component of the intake swirl flow generated in the cylinder is increased in the operating state in which the air regulating valve is closed, and the power of the intake swirl flow is attenuated as the piston reaches the top dead center. And stratification of the air-fuel mixture for collecting fuel near the spark plug is achieved.

In the intake system for an internal combustion engine according to the present invention, the ratio of the cross-sectional area of the air passage to the cross-sectional area of the mixture passage is constant, and the maximum width in the lateral direction gradually increases from the upstream side to the downstream side. By having a portion that increases, the cross-sectional shape of the intake passage is made closer to a circle at a portion where the intake port is connected to the intake manifold, so that the flow of intake air from the intake manifold to the intake port is smooth, and the cylinder head and the intake manifold are connected. The sealing property between them can be enhanced.

The intake system for an internal combustion engine according to claim 8, wherein the ratio of the cross-sectional area of the air passage to the cross-sectional area of the air-fuel mixture passage gradually decreases from the upstream side to the downstream side of the intake passage. The velocity component of the airflow flowing from the passage toward the outer periphery of the cylinder is appropriately increased, and stratification of the air-fuel mixture for collecting fuel near the spark plug is achieved.

In the intake system for an internal combustion engine according to the ninth aspect, an air regulating valve disposed in a mixture passage connected to the left and right banks of the V-type internal combustion engine is driven to open and close via a common shaft. The structure can be simplified as compared with a structure in which a drive system for each air adjustment valve is independently provided for each of the left and right banks.

[0033] In the intake device for an internal combustion engine according to the tenth aspect, most of the intake air flows from the outer periphery of the cylinder through the air passage by closing the air regulating valve in a low speed and low load region. At this time, the rich air-fuel mixture is introduced from the air-fuel mixture passage near the center of the cylinder, so that an intake air swirl flow is generated in the cylinder in which two-layered intake air consisting of the rich air-fuel mixture and the air flow is swirled, and ignition occurs. A stratification of the air-fuel mixture for collecting fuel near the stopper is achieved.

When the engine control valve is opened and the engine load or the rotational speed is higher than a predetermined value, the air control valve is maintained at the fully open position, and the intake air flow rates of the mixture passage and the air passage are made substantially equal. . At this time, the tumble component of the swirling flow generated in the cylinder is increased, and the fuel injected into the air-fuel mixture passage flows into the cylinder while sufficiently mixing with the air, whereby a homogeneous air-fuel mixture is formed in the cylinder.

In the intake system for an internal combustion engine according to the eleventh aspect, since the downstream edge of the partition faces the back of the umbrella of the intake valve, the air-fuel mixture sucked into the cylinder from the air-fuel mixture passage passes through the partition. Thus, the air-fuel mixture is guided to a position immediately upstream of the back of the umbrella of the intake valve to enhance the effect of separating the air from the air passage into the cylinder, and stratification of the air-fuel mixture for collecting fuel near the ignition plug is achieved.

[0036]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, one intake passage 9 and one exhaust passage 15 are connected to the cylinder 1 respectively. In the plan view of FIG. 1, the intake passage 9 and the exhaust passage 1
5 extend in parallel so as to face each other, and the center of each passage is offset in the opposite direction to the center of the cylinder 1.

One ignition plug 4 facing the cylinder 1 is provided. In the plan view of FIG.
, And is disposed substantially on the center of the exhaust passage 15 so as to face the exhaust passage 15.

The intake passage 9 and the exhaust passage 15 are opened and closed by a single intake valve 2 and a single exhaust valve 3, respectively. The intake valve 2 and the exhaust valve 3 open and close at a predetermined timing synchronized with the rotation of the engine.

As the piston descends and the intake valve 2 is opened, intake air (air-fuel mixture) is sucked into the cylinder 1 from the intake passage 9, compressed by the piston, and ignited through the ignition plug 4. After burning and lowering the piston, the exhaust is discharged from the exhaust passage 15 with the rise of the piston and the opening of the exhaust valve, and each of these steps is continuously repeated.

A throttle valve (not shown) is provided in the middle of the intake passage 9. The throttle valve is interlocked with an accelerator pedal (not shown) and opens as the driver depresses the accelerator pedal to increase the amount of intake air drawn into the cylinder 1.

The intake passage 9 is connected to the mixture passage 8 through the partition 6.
And the air passage 7. A fuel injection valve 5 for injecting fuel toward the mixture passage 8 is provided.

The fuel spray injected from the fuel injection valve 5 into the air-fuel mixture passage 8 is, as shown by a two-dot chain line in FIG.
Spreads radially toward the back of the umbrella. Thus, the fuel injected from the fuel injection valve 5 is guided to the cylinder 1 while mixing with the intake air passing through the mixture passage 8.

A control unit (not shown) inputs an intake air amount Qa detected by an air flow meter, an engine speed N detected by an engine speed sensor, a cooling water temperature Tw detected by a cooling water temperature sensor, and the like. The fuel injection amount is calculated according to the operating state, and a pulse signal corresponding to the calculated fuel injection amount is output to the fuel injection valve 5 to control the fuel injection amount. The air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 is made leaner than the stoichiometric air-fuel ratio in a lean burn region where the engine load is equal to or less than a predetermined value. The air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 is controlled near the stoichiometric air-fuel ratio under operating conditions other than the lean burn region where the engine load rises above a predetermined value.

The mixture passage 8 communicates near the center of the cylinder 1. The air passage 7 communicates with the outer periphery of the cylinder 1,
The connection is made in a substantially tangential direction of the cylinder 1 on the plan view of FIG.

A butterfly type air regulating valve 10 is interposed in the mixture passage 8. The air adjustment valve 10 is opened and closed by an unillustrated control unit via an actuator in accordance with engine operating conditions. Under operating conditions in which the engine load is outside the lean burn region where the engine load is higher than a predetermined value, the air regulating valve 10 is held at the fully open position, and the intake air flow rates in the mixture passage 8 and the air passage 7 are made substantially equal. At this time, cylinder 1
As a result, the tumble component of the swirling flow generated in the air is increased, and the fuel injected into the air-fuel mixture passage 8 flows into the cylinder 1 while sufficiently mixing with the air, so that a homogeneous air-fuel mixture is formed in the cylinder 1.

In an operating condition in which the engine load is in a lean combustion region of a predetermined value or less, the air regulating valve 10 is held in the closed position, and most of the intake air is passed through the air passage 7 to the cylinder 1 from its tangential direction. Let it flow in. At this time, a rich mixture is introduced near the center of the cylinder 1 from the mixture passage 8 as shown by the arrow B in the figure, while near the outer periphery of the cylinder 1 from the air passage 7 as shown by the arrow C in the figure. High-speed air is introduced into the air. As a result, an intake swirl flow is generated in the cylinder 1 in which a two-layered intake air composed of a rich mixture and an air flow swirls, and stratification of the air-fuel mixture for collecting fuel near the ignition plug 4 is achieved.

However, in the lean burn region, the air regulating valve 1
If the ratio of the swirl component or the tumble component of the intake swirling flow generated in the cylinder 1 is not appropriate while holding 0 in the closed position, the power of the intake swirling flow is attenuated as the piston reaches the top dead center. Thus, stratification of the air-fuel mixture for collecting fuel near the ignition plug 4 is not achieved.

In accordance with the present invention, the cross-sectional area S ₈ of the mixture passage 8 is formed to be larger than the cross-sectional area S ₇ of the air passage 7.

In the present embodiment, the ratio S of the cross-sectional area S ₇ of the sectional area _{S 8} and the air passage 7 of the mixture passage 8 _8: S ₇ to 6: 4
Set to.

As described above, by setting the sectional area S ₈ of the mixture passage 8 to be larger than the sectional area S ₇ of the air passage 7 at a ratio of 6: 4, the operation state in which the air regulating valve 10 is closed can be achieved. 1, the velocity component of the airflow flowing from the air passage 7 toward the outer periphery of the cylinder 1 can be increased appropriately.

The air passage 7 has its passage center line O ₇ farther from the ignition plug 4 than the passage center line O _{8 of the} mixture passage 8, and is located below the passage center line O ₈ of the mixture passage 8. Formed.

The lower portion of the partition wall 6 is formed to be curved toward the mixture passage 8 so that the lower portion of the air passage 7 is located below the mixture passage 8.

The cross-sectional area of the air passage 7 is gradually increased from the upper part to the lower part in the lower part, and the cross-section of the bottom part 14 extends in a horizontal straight line.

As the cross-sectional area of the air passage 7 expands in the lower portion, the intake air swirl generated in the cylinder 1 as indicated by an arrow C in FIG. By increasing the tumble component of the flow, the power of the intake swirling flow is suppressed from attenuating as the piston reaches the top dead center, and stratification of the air-fuel mixture that collects fuel near the spark plug 4 is achieved.

The downstream edge 6a of the partition 6 is disposed immediately upstream of the umbrella back portion 19a of the intake valve 2 in the closed position.
Is facing the back of the umbrella.

In this case, the air-fuel mixture and the air sucked into the cylinder 1 from the air-fuel mixture passage 8 with the opening of the intake valve 2 flow through the partition 6 to a position immediately upstream of the back of the umbrella of the intake valve 2. The mixture which is guided separately and collects fuel near the ignition plug 4 is stratified.

In this way, by optimizing the power of the intake swirl flow generated in the cylinder 1, the ignition plug 4
The stratification of the air-fuel mixture that collects the fuel in the vicinity of, and stable combustion can be obtained even with a lean air-fuel mixture. As a result, it is possible to prevent misfire or deterioration of exhaust emission due to cycle fluctuation.

Next, as an embodiment shown in FIG. 3, the air-fuel mixture passage 8 has a cross-sectional area which expands from below to above.
It is formed with an inverted triangular cross section.

The air passage 7 has a triangular cross-sectional shape whose cross-sectional area increases from the upper side to the lower side. The cross section of the bottom portion 14 of the air passage 7 extends horizontally in a straight line, and the cross section of the side portion 15 extends in a straight line inclined downward.

[0061] the horizontal plane L ₈ intersecting the passageway centerline O ₈ of the mixture passage 8, passage center line O ₈ of mixture passage 8 and the air passage 7
Is set to an angle of about 45 degrees to make the line segment S ₇ connecting the passage center line O _7.

Most of the air passage 7 is located below the mixture passage 8. Partition 6 its cross-section is formed in a linear shape, and extends so as to be substantially perpendicular to the line segment S _1.

With the structure described above, the cross-sectional area of the air passage 7 can be maximized at its lower portion. Thereby, in the operation state in which the air regulating valve 10 is closed, the tumble component of the intake swirl flow generated in the cylinder 1 is increased as shown by an arrow C in FIG. 3, and as the piston reaches the top dead center. The power of the intake swirling flow is suppressed from attenuating,
A stratification of the air-fuel mixture for collecting fuel near the spark plug 4 is achieved.

Next, as an embodiment shown in FIG. 4, the air passage 7 is formed to have a triangular cross-sectional shape whose cross-sectional area increases from the upper side to the lower side. The air passage 7 has a cross section of a bottom portion 14 extending in a horizontal straight line and a side portion 15 thereof.
Cross section extends in a vertical straight line.

In this case, most of the air passage 7 is disposed below the mixture passage 8, and the cross-sectional area of the air passage 7 can be maximized below the air passage 7. Thereby, in the operation state in which the air regulating valve 10 is closed, the tumble component of the intake swirl flow generated in the cylinder 1 is increased as shown by the arrow C in FIG. 4, and as the piston reaches the top dead center. As a result, the power of the intake swirling flow is suppressed from attenuating, and stratification of the air-fuel mixture for collecting fuel near the ignition plug 4 is achieved.

Next, as an embodiment shown in FIG. 5, the air passage 7 is formed such that the maximum lateral widths D ₃ , D ₂ and D ₁ of the cross section gradually increase from the downstream side to the upstream side.

[0067] mixture passage 8 of the cross-sectional area S ₈ and the ratio S of the cross-sectional area S ₇ of the air passage 7 _8: S ₇ in substantially the entire area 6: is set to 4.

In this case, the cross-sectional shape of the intake passage 9 is made closer to a circle at a portion where the intake port is connected to an intake manifold (not shown), so that the flow of intake air from the intake manifold to the intake port is smooth, and the cylinder head and the intake Sealability between manifolds can be improved.

Next, as an embodiment shown in FIG. 6, the air passage 7 is formed such that the maximum lateral width of its cross section gradually decreases from the upstream side to the downstream side.

[0070] The ratio S of the cross-sectional area S ₇ of the sectional area S ₈ and the air passage 7 of the mixture passage 8 _8: S _7, with its upstream end 6: is set to 4, the cross-sectional of the mixture passage 8 toward the downstream side The air passage 7 is formed such that the ratio of the cross-sectional area S ₇ of the air passage 7 to the area S ₈ becomes gradually smaller.

In this case, in the operation state in which the air regulating valve 10 is closed, the velocity component of the air flow flowing from the air passage 7 toward the outer periphery of the cylinder 1 is further increased as indicated by an arrow C in FIG. A stratification of an air-fuel mixture for collecting fuel near the stopper 4 is performed.

Next, the embodiment shown in FIGS. 7 and 8 will be described. The parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

An intake manifold 22 is connected between the banks of the cylinder head 20 of the V-type engine, and the air adjusting valve 10 is interposed in the intake manifold 22.

The intake air taken from the air cleaner is
The air flows into the intake manifold 22 through the throttle chamber 23, and is distributed from the intake manifold 22 to the intake ports of each cylinder.

The throttle chamber 23 is provided with a butterfly type throttle valve 21. The throttle valve 21 is operated in conjunction with an accelerator pedal (not shown), and opens as the driver depresses the accelerator pedal to increase the amount of intake air drawn into the cylinder 1.

Also in the present embodiment, the intake passage 9 is divided into the mixture passage 8 and the air passage 7 through the partition 6. A fuel injection valve 5 for injecting fuel toward the mixture passage 8 is provided.

Each air regulating valve 10 provided in each mixture passage 8 connected to the left and right banks is driven to open and close via a common shaft 17.

Each air regulating valve 10 is opened and closed by a single actuator via a shaft 17. This simplifies the structure as compared with a structure in which a drive system for each air adjustment valve 10 is independently provided for each of the left and right banks.

As another embodiment, as shown in FIG.
The partition wall 6 may have a structure that partitions the intake passage 9 as an independent intake pipe between the mixture passage 8 and the air passage 7.

In this case, the degree of freedom for setting the length of each of the mixture passage 8 and the air passage 7 is increased.

As another embodiment, as shown in FIG. 10, the partition 6 has a structure in which the intake passage 9 partitions the mixture passage 8 and the air passage 7 as independent intake pipes, and the air passage 7 is separated from the mixture passage 8. It may be formed long. As a result, the intake charging efficiency in the low speed range can be increased.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a cross-sectional view showing another embodiment.

FIG. 4 is a sectional view showing still another embodiment.

FIG. 5 is a schematic plan view and a cross-sectional view showing still another embodiment.

FIG. 6 is a schematic plan view showing still another embodiment.

FIG. 7 is a schematic plan view showing still another embodiment.

FIG. 8 is a schematic front view of the same.

FIG. 9 is a schematic plan view showing still another embodiment.

FIG. 10 is a schematic plan view showing still another embodiment.

FIG. 11 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Intake valve 3 Exhaust valve 4 Spark plug 5 Fuel injection valve 6 Partition wall 7 Air passage 8 Mixture passage 9 Intake passage 10 Air control valve

Claims (11)

[Claims] 1. An intake passage for guiding intake air to one cylinder, a single intake valve for opening and closing the intake passage in synchronization with engine rotation, an exhaust passage for discharging exhaust from the cylinder, and an exhaust passage for engine rotation. In an internal combustion engine comprising: a single exhaust valve that opens and closes in synchronism; and an ignition plug that faces the cylinder substantially opposite to the exhaust valve, an air-fuel mixture passage that opens the intake passage toward the center of the cylinder and an outer periphery of the cylinder A fuel injection valve for supplying fuel to the air-fuel mixture passage, and an air regulating valve for narrowing the air-fuel mixture passage according to the operating condition. An intake device for an internal combustion engine, wherein the intake device is formed to have a larger cross-sectional area. 2. A ratio of a cross-sectional area of the mixture passage to a cross-sectional area of the air passage is set to approximately 6: 4.
An intake device for an internal combustion engine according to claim 1. 3. A center line of the air passage is farther from the spark plug than a center line of the mixture passage, and a center line of the air passage is disposed below the center line of the mixture passage. 3. The intake device for an internal combustion engine according to claim 1, wherein 4. An angle between a horizontal plane intersecting with the passage center line of the mixture passage and a line connecting the passage center line of the mixture passage and the center line of the air passage is set to about 45 degrees. Item 4. An intake device for an internal combustion engine according to any one of Items 1 to 3. 5. The intake device for an internal combustion engine according to claim 1, wherein at least a part of the air passage is disposed below the mixture passage. 6. The air-fuel mixture passage has a portion whose cross-sectional area increases from bottom to top, and the air passage has a portion whose cross-section increases from top to bottom. 6. The intake device for an internal combustion engine according to any one of claims 1 to 5. 7. The air-fuel mixture passage is characterized in that the ratio of the cross-sectional area of the air passage to the cross-sectional area thereof is constant, and that the mixture passage has a portion where the maximum width in the lateral direction gradually increases from the upstream side to the downstream side. The intake device for an internal combustion engine according to any one of claims 1 to 6. 8. The air-fuel mixture passage according to claim 1, wherein a ratio of a cross-sectional area of the air passage to a cross-sectional area thereof gradually decreases from an upstream side to a downstream side of the intake passage. An intake device for an internal combustion engine according to any one of the preceding claims. 9. The V-type internal combustion engine according to claim 1, wherein an air regulating valve interposed in the mixture passage connected to the left and right banks is driven to open and close via a common shaft. An intake device for an internal combustion engine according to any one of the preceding claims. 10. The intake device for an internal combustion engine according to claim 1, wherein the air regulating valve is configured to be closed in a low speed and low load range. 11. A partition wall for partitioning the intake passage into an air-fuel mixture passage and an air passage, wherein a downstream edge of the partition wall is formed to face an umbrella back portion of the intake valve. An intake device for an internal combustion engine according to any one of the above.