JP3329169B2 - In-cylinder direct 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 in-cylinder direct injection type internal combustion engine in which fuel is directly injected into a cylinder and spark ignition is performed by a spark plug. .

[0002]

2. Description of the Related Art Conventionally, as a structure of a piston crown surface in a direct injection type internal combustion engine of this kind, there is one as shown in FIG. 6 (see Japanese Patent Application Laid-Open No. H05-240047). In other words, this increases the generation of the reverse tumble vortex 6 of the intake air from the intake port 7 in the combustion chamber 3 formed between the crown surface 1A of the piston 1 and the lower surface of the cylinder head 2. A concave portion 4 having a downwardly curved surface is formed on one side (for example, the intake side) of the surface 1A, and the concave portion 4 is gently raised from the concave portion 4 and the lower surface of the cylinder head 2 at the top dead center of the piston 1. Is formed with a protruding portion 5 close to.

[0003]

However, in such a conventional in-cylinder direct injection type internal combustion engine, the piston crown 1
In the structure A, the recess 4 having a downwardly curved surface is formed on one side (for example, the intake side) of the piston crown surface 1A, but is formed on the other side (for example, the exhaust side), that is, Since the piston crown surface 1A on the opposite side of the recess 4 from the raised portion 5 is flat, when the fuel hits this flat surface, the fuel is liable to be attached and the vicinity of the top dead center. In the above, the gas flow in the cylinder including the reverse tumble vortex 6 is easily weakened, and as a result,
Poor vaporization of the fuel attached as described above.

Further, since the piston crown surface 1A in the portion where the raised portion 5 is formed is flat, the space where the intake air exists between the raised portion 5 and the lower surface of the cylinder head 2 is reduced. There is a relatively high possibility that soot and unburned fuel emission will increase and the engine output will decrease. Therefore,
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to improve fuel vaporization and engine output by improving the shape of a piston crown in an in-cylinder direct injection internal combustion engine.

[0005]

For this reason, the invention according to claim 1 is characterized in that a fuel is injected by a fuel injection valve disposed on an intake side wall surface of a combustion chamber formed between a piston crown surface and a cylinder head lower surface. In a direct injection type internal combustion engine in which fuel is directly injected into a chamber and spark ignition is performed by a spark plug arranged at a substantially central portion of a wall facing a piston crown of a combustion chamber,
In the intake-side portion and the exhaust-side portion of the piston crown surface, a crossing line extends in a direction along a line substantially orthogonal to a line connecting the intake side and the exhaust side, and is located near the ignition plug at the piston top dead center. Such concave curved surfaces are respectively formed, and a substantially mountain-like protruding portion having the intersection line as a ridge line is formed on the piston crown surface by the biconcave curved surface, and is substantially opposed to the spark plug at the top of the protruding portion. Formed on the exhaust side of the crown of the piston.
The tumble vortex generated on the concave surface by the concave surface
During the compression stroke .

In the invention according to the first aspect, the fuel is injected from the fuel injection valve toward a concave curved surface formed on the intake side of the piston crown surface. At this time, the fuel spray injected into the combustion chamber is formed on the exhaust side of the piston crown surface beyond the formation region of the intake side concave curved surface due to the width of the spray angle of the spray itself and the diffusion of the fuel due to the gas flow in the combustion chamber. Wrap around to the concave surface. Alternatively, part of the fuel spray directly reaches the concave curved surface on the exhaust side.

[0007] In this case, the tumble vortex generated on the concave curved surface on the exhaust side is retained for a relatively long time even in the compression stroke due to the concave curved surface on the exhaust side. Is promoted. or,
Since a concave curved surface is also formed on the exhaust side portion, a relatively large space portion is formed on the exhaust side where the fuel spray flows by its own penetration force and gas flow in the combustion chamber, Even when the fuel burns, the fuel adhering to the piston crown surface is unlikely to cause incomplete combustion due to lack of oxygen, so that an increase in soot generation and unburned fuel generation is suppressed.

Further, when the piston rises to the vicinity of the top dead center, the tumble vortex is held relatively more strongly in the concave portion of the piston crown surface facing the spark plug than in other portions, so that the fuel is vaporized. Further promoted, vaporized fuel is concentrated around the spark plug. As a result, the vaporized fuel density around the ignition plug increases, and the ignitability improves.

By improving the ignitability as described above,
The engine stability at the time of an idling operation of an engine with a minimum amount of fuel or in a lean operation region is improved. In particular, when fuel is injected into the combustion chamber during the compression stroke of the engine, the amount of fuel adhering to the piston crown surface increases and the time until ignition is short, so that the tumble vortex in the combustion chamber is compressed at the top dead center. It is important that the fuel gas is accelerated and vaporized, and the vaporized fuel is collected around the spark plug and stratified and burned. Such stratified combustion is effectively performed, and the effect of enhancing the engine stability in the engine idling operation and in the lean operation region as described above is exerted.

[0010] In the invention according to claim 2, the concave curved surface is formed in a cylindrical shape. In the invention according to the second aspect, the piston crown surface is formed by a substantially concave curved surface and the flat surface is reduced, so that the tumble vortex is held over a wide range of the piston crown surface, whereby the fuel winding effect can be sufficiently obtained. This promotes uniform diffusion of the fuel into the combustion chamber.

According to a third aspect of the present invention, the concave curved surface is formed in a spherical shape. In the invention according to claim 3, since the concave curved surface is formed in a spherical shape, the fuel spray is prevented from spreading in a direction along a line substantially perpendicular to a line connecting the intake side and the exhaust side, and the Since the air approaches the center of the piston crown, the amount of fuel adhering to the piston crown is further reduced.

According to a fourth aspect of the present invention, the concave curved surface is formed into a flat disk shape substantially in the axial direction of the piston. In the invention according to claim 4, since the concave curved surface is formed in the shape of a disk, the fuel spray is prevented from spreading in a direction along a line substantially orthogonal to a line connecting the intake side and the exhaust side, Since the mixture is shifted toward the center of the piston crown, the amount of fuel adhering to the piston crown is further reduced, and the flat portion of the periphery of the piston crown can be eliminated, thus tumbling over a wide area of the piston crown. The eddy current is maintained, and the effect of raising the fuel is sufficiently obtained, so that uniform diffusion of the fuel into the combustion chamber is promoted.

According to a fifth aspect of the present invention, the inner surface of the recess is formed in a spherical shape. In the invention according to the fifth aspect, the vaporized fuel is more concentratedly collected around the spark plug by the concave portion having the spherical inner surface. According to a sixth aspect of the present invention, the inner surface of the recess is formed in a flat disk shape in a direction substantially perpendicular to the axial direction of the piston and substantially perpendicular to the direction connecting the intake side and the exhaust side.

In the invention according to claim 6, since the width of the recess in the direction substantially perpendicular to the direction connecting the intake side and the exhaust side can be formed narrow, the vaporized fuel is ignited. The effect that the tumble vortex can be held more effectively near the compression top dead center while the effect of collecting the fuel around the plug and stratifying combustion is exerted, and the vaporized fuel is more concentrated around the ignition plug.

According to a seventh aspect of the present invention, the piston crown surface and the shell
Intake side wall of combustion chamber formed between the lower surface of the Linda head
Fuel is injected directly into the combustion chamber by a fuel injection valve
Injects, approximately at the center of the wall facing the piston crown of the combustion chamber
In cylinder direct injection internal combustion engine which performs spark ignition by disposed ignition plug part, and the intake port of the piston crown surface
A concave curved surface on the intake side is formed on the facing part, while the piston
A tumble vortex is created at the part of the crown facing the exhaust port.
An exhaust-side concave surface to be generated and held is formed, and an intersection line between the intake-side concave surface and the exhaust-side concave surface is formed on a piston crown surface.
Ridge is formed to bulge in a substantially mountain shape as a line, the spark plug is substantially opposite to the site of the top of the ridge, and to form a recess in which the inner surface is formed into a curved surface.

According to the seventh aspect of the present invention, the tumble vortex generated on the exhaust-side concave curved surface is held for a relatively long time even in the compression stroke because of the presence of the exhaust-side concave curved surface. Vaporization is promoted, homogenization of the air-fuel mixture is promoted, and a concave curved surface is also formed on the exhaust side, so that fuel spray is caused by its own penetration force and the flow of gas in the combustion chamber on the exhaust side. Therefore, a relatively large space is formed, and even when the fuel burns, the fuel adhering to the piston crown surface is unlikely to cause incomplete combustion due to lack of oxygen, soot generation and unburned fuel The increase in occurrence is suppressed.

Further, stratified combustion is effectively performed by the concave portion facing the spark plug on the piston crown surface, and the engine stability at the time of idling operation of the engine and in the lean operation region is enhanced.

[0018]

According to the first and seventh aspects of the present invention, the vaporization of fuel is promoted, the homogenization of the air-fuel mixture is promoted, and the fuel adheres to the piston crown even when burning. Fuel is less likely to cause incomplete combustion due to lack of oxygen, so it is possible to suppress the increase in soot generation and unburned fuel generation.
I can .

According to the second aspect of the present invention, since the flat surface of the piston crown is reduced, the tumble vortex is maintained over a wide range of the piston crown, and uniform diffusion of the fuel into the combustion chamber is promoted. According to the third aspect of the invention, the amount of fuel adhering to the piston crown surface can be further reduced, and the increase in soot generation and unburned fuel generation can be more effectively suppressed.

According to the fourth aspect of the present invention, the amount of fuel adhering to the piston crown surface can be further reduced, soot generation and unburned fuel generation can be more effectively suppressed, and the fuel consumption can be reduced. Uniform diffusion into the combustion chamber is further promoted.
According to the fifth aspect of the present invention, the vaporized fuel can be more concentratedly collected around the spark plug by the concave portion having the spherical inner surface.

According to the sixth aspect of the present invention, the effect that the vaporized fuel is collected around the ignition plug to perform stratified combustion, and that the tumble vortex flow can be more effectively maintained even near the compression top dead center. Therefore, the vaporized fuel can be more concentratedly collected around the spark plug.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 1 shows the present invention (claims 1, 2, 5).
And FIG. 7 is a sectional view of a cylinder structure showing an embodiment of a direct injection type internal combustion engine according to the present invention, wherein a combustion chamber 1 is provided between a crown 10A of a piston 10 and a lower surface of a cylinder head 11.
2 are formed, and two exhaust ports are arranged in parallel with two intake ports 13 arranged in parallel on a wall of a cylinder head 11 above the combustion chamber 12, that is, a wall of a cylinder head combustion chamber 12 </ b> A formed below the cylinder head 11. The intake port 13 is provided with an intake valve 15, and the exhaust port 14 is provided with an exhaust valve 16.

A fuel injection valve 17 is disposed between the intake ports 13 on the side wall surface of the cylinder head 11 where the intake port 13 is formed so as to have an appropriate angle with respect to the piston crown surface 10A. The cylinder head 11 wall surface facing the crown surface 10A, that is, the cylinder head combustion chamber 12
A spark plug 18 is disposed substantially at the center of the wall surface of A.

Here, in the present invention, as shown in FIGS. 1 to 4, the intake side portion (a portion facing the intake port 13) and the exhaust side portion (the exhaust port 1) of the piston crown surface 10A.
4), a concave curved surface whose mutual intersection line extends in a direction along a line substantially orthogonal to a line connecting the intake side and the exhaust side, and is located near the ignition plug 18 at the top dead center of the piston 10. 19A and 19B are formed respectively, and a substantially mountain-shaped raised portion 20 having the intersection line as a ridgeline 20A is formed on the piston crown surface 10A by the biconcave curved surfaces 19A and 19B.

In the present invention, as shown in FIGS. 1 to 4, a concave portion 2 having a curved inner surface is provided at a portion of the top of the raised portion 20 substantially opposite to the spark plug 18.
2 is formed. In the present embodiment,
The concave curved surfaces 19A and 19B are each formed in a cylindrical shape, and the inner surface of the concave portion 22 is formed in a spherical shape.

In FIG. 3, A is indicated by a dashed line.
Indicates a spherical shape from which the inner surface of the recess 22 is formed. Next, the operation of such a configuration will be described.
The fuel is supplied to the fuel injection valve 1 disposed between the intake ports 13.
7, the fuel is injected toward a concave curved surface (hereinafter, intake-side concave curved surface) 19A formed on the intake side of the piston crown surface 10A.

At this time, the fuel spray injected into the combustion chamber 12 is mixed with the intake air by the kinetic energy of the spray itself and the diffusion of the fuel. And the piston crown 10A
Are provided with two concave curved surfaces 19A and 19B on the intake side and the exhaust side which hold the tumble vortex in the combustion chamber 12, so that fuel vaporization is promoted.

That is, the fuel spray injected into the combustion chamber 12 crosses the region where the concave curved surface 19A on the intake side is formed due to the width of the spray angle of the spray itself and the diffusion of fuel due to the gas flow in the combustion chamber 12, and the piston crown. It goes around to a concave curved surface (hereinafter, exhaust-side concave curved surface) 19B formed on the exhaust side of the surface 10A.
Alternatively, a part of the fuel spray directly reaches the exhaust-side concave curved surface 19B.

In this case, the tumble swirl 21 generated on the exhaust-side concave curved surface 19B is retained for a relatively long time even in the compression stroke due to the existence of the exhaust-side concave curved surface 19B, and fuel vaporization is promoted. Thus, the homogenization of the mixture is promoted. Further, since the concave curved surface 19B is also formed in the exhaust side portion (the portion facing the exhaust port 14), the fuel spray is compared on the exhaust side where the fuel spray flows due to its own penetration force and the gas flow in the combustion chamber. When the fuel burns, the fuel adhering to the piston crown 10A is less likely to undergo incomplete combustion due to lack of oxygen, so that soot or unburned fuel is generated. Increase can be suppressed.

In particular, in this embodiment, the piston crown surface 10A can be formed by a substantially concave curved surface, and the flat surface can be reduced, so that the tumble vortex flow can be held over a wide range of the piston crown surface 10A, and the fuel winding effect by this can be reduced. Since it is obtained sufficiently, uniform diffusion of fuel into the combustion chamber can be promoted. Furthermore, when the piston 10 rises to the vicinity of the top dead center, the tumble vortex is held relatively stronger in the recess 22 of the piston crown surface 10A opposed to the spark plug 18 than in other parts, so that the fuel is vaporized. Is further promoted, and the vaporized fuel is concentrated around the spark plug 18.

As a result, the vaporized fuel density around the spark plug 18 increases, and the ignitability improves. Particularly, in this embodiment, since the inner surface of the concave portion 22 is formed in a spherical shape, there is an advantage that the vaporized fuel can be more intensively collected around the ignition plug 18. By improving the ignitability in this way, the engine stability at the time of the idling operation or the lean operation region of the engine having a very small amount of fuel can be enhanced.

In particular, when fuel is injected into the combustion chamber during the compression stroke of the engine, the amount of fuel adhering to the piston crown surface increases and the time until ignition is short, so that the tumble vortex in the combustion chamber is compressed. It is important that the fuel be held strongly up to the top dead center to promote the vaporization of the fuel, and that the vaporized fuel be collected around the spark plug and stratified and combusted. Recess 22
Has the effect of effectively performing such stratified combustion and increasing the engine stability in the above-described idle operation and lean operation regions of the engine.

FIG. 5 shows the present invention (claims 1, 2, 6 and 7).
FIG. 1 is a perspective view of a piston showing an embodiment of a direct injection type internal combustion engine according to the present invention). In this embodiment, a concave portion 32 of a piston crown surface 10A facing a spark plug 18 is formed by a piston 10 shaft. It is formed in a flat disk shape in a direction substantially perpendicular to the direction and substantially perpendicular to the direction connecting the intake side and the exhaust side.

In FIG. 5, B indicated by a chain line
Indicates a disk shape from which the inner surface of the recess 32 is formed. The recess 32 of such an embodiment is shown in FIGS.
As compared with the concave portion 22, the width in the direction substantially perpendicular to the direction connecting the intake side and the exhaust side can be formed to be narrower, so that the vaporized fuel is collected around the ignition plug 18 and stratified. This has the advantage that the tumble vortex can be more effectively held near the compression top dead center while having the effect of burning, and the vaporized fuel is more easily concentrated around the spark plug 18.

In addition, instead of the cylindrical concave surfaces 19A and 19B of the embodiment of FIGS. 1 to 5, a spherical concave surface or a substantially piston A disk-shaped concave curved surface that is flat in the axial direction may be formed. When the concave curved surface is formed in a spherical shape, it is possible to suppress the fuel spray from spreading in a direction along a line substantially perpendicular to a line connecting the intake side and the exhaust side, and to control the air-fuel mixture on the piston crown surface 1.
Since the fuel can be brought closer to the center of 0A, the effect that the amount of fuel adhering to the piston crown surface 10A can be further reduced can be obtained.

In the case where the concave curved surface is formed in the shape of a disk, the spread of the fuel spray in a direction substantially perpendicular to the line connecting the intake side and the exhaust side can be suppressed, and the air-fuel mixture can be prevented from flowing into the piston crown surface. Since the fuel can be brought closer to the center of the piston crown 10A, the amount of fuel adhering to the piston crown 10A can be further reduced, and the flat portion of the periphery of the piston crown 10A can be eliminated. Since the tumble vortex can be held over a wide range and the fuel can be sufficiently taken up by this, the uniform diffusion of the fuel into the combustion chamber can be promoted.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the invention described in claims 1, 2, 5, and 7;

FIG. 2 is a perspective view of a piston according to the embodiment.

FIG. 3 is a perspective view of a piston according to the embodiment.

FIG. 4 is a front view of the piston according to the embodiment.

FIG. 5 is a perspective view of a piston showing one embodiment of the invention described in claims 1, 2, 6, and 7;

FIG. 6 is a schematic view showing a piston structure of a conventional direct injection type internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piston 10A Piston crown surface 11 Cylinder head 12 Cylinder head 12 Combustion chamber 12A Cylinder head combustion chamber 13 Intake port 14 Exhaust port 17 Fuel injection valve 18 Spark plug 19A, 19B Concave curved surface 20 Raised portion 20A Ridge line 22 Depressed portion 32 Depressed portion

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Claims (7)

(57) [Claims] 1. A fuel injection valve disposed on an intake side wall of a combustion chamber formed between a piston crown and a lower surface of a cylinder head injects fuel directly into the combustion chamber. In an in-cylinder direct-injection internal combustion engine in which spark ignition is performed by a spark plug disposed at a substantially central portion of an opposed wall surface, a crossing line is formed between an intake side and an exhaust side of a piston crown surface. Protruding in a direction substantially along a line substantially perpendicular to the line connecting the two and forming concave concave surfaces located near the ignition plug at the piston top dead center, and protruding in a substantially mountain-like shape having the intersection line as a ridge line. parts formed on the piston crown surface by the two concave surfaces, the spark plug substantially phase opposite sites of the top of the raised portion to form a recess in which the inner surface is formed into a curved surface, the exhaust side of the piston crown surface The concave surface formed on the part
During the compression stroke, the tumble vortex generated on the concave surface
An in-cylinder direct injection internal combustion engine characterized in that it is held . 2. An in-cylinder direct injection internal combustion engine according to claim 1, wherein said concave curved surface is formed in a cylindrical shape. 3. An in-cylinder direct injection internal combustion engine according to claim 1, wherein said concave curved surface is formed in a spherical shape. 4. An in-cylinder direct injection internal combustion engine according to claim 1, wherein said concave curved surface is formed in a disk shape that is flat in a substantially axial direction of the piston. 5. An in-cylinder direct injection internal combustion engine according to claim 1, wherein an inner surface of said recess is formed in a spherical shape. 6. The disk drive according to claim 1, wherein an inner surface of said recess is formed in a flat disk shape in a direction substantially perpendicular to a piston axial direction and substantially perpendicular to a direction connecting an intake side and an exhaust side. An in-cylinder direct injection internal combustion engine according to any one of the above. 7. Between a piston crown surface and a cylinder head lower surface.
Injection disposed on the intake side wall of the combustion chamber formed at the bottom
The fuel is directly injected into the combustion chamber by the valve, and the combustion chamber is fixed.
Ignition plug located at the approximate center of the wall facing the crown
In- cylinder direct-injection internal combustion engine that performs spark ignition by sparking , the intake-side concave
While forming a curved surface , tumble the part facing the exhaust port on the piston crown.
An exhaust-side concave curved surface for generating and holding a vortex is formed, and the intake-side concave curved surface and the exhaust-side concave curved surface are formed on a piston crown surface.
Forming a raised portion that protrudes in a substantially mountain-like shape with the intersection line as a ridge line, and a portion of the top of the raised portion substantially facing the spark plug;
An in- cylinder direct-injection internal combustion engine, wherein a concave portion having an inner surface formed into a curved surface is formed.