JP2000120440A - Cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the feeding properties of fuel atomization around each ignition plug, and try to restrain the adhesion of fuel onto the wall surface. SOLUTION: The preservation of a forward tumble flow A in a circular arc shaped recessed part 17 at the disposition side of a recessed part 15 in a ω shape in cross section provided for the crown surface of a piston 2 at the time of stratified charge combustion, the restraint of gas dispersion in the right and left directions of fuel atomization F injected out of a fuel injection valve 10 at its compression stroke while being guided by both the wall sides of a circular arc shaped recessed part 16 at the disposition side of a suction valve and concurrently, the restraint of the fuel adhesion onto a center projected part 18 offset to the exhaust valve disposition side, thereby allow the vaporization of fuel to be accelerated, concurrently, allow the dispersion of fuel to the exhaust valve disposition side to be restrained, also allow the feeding properties of fuel atomization F around an ignition plug 9 to be enhanced, and thereby enable the improvement of exhaust properties to be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a direct injection type spark ignition engine.

[0002]

2. Description of the Related Art In a direct injection type spark ignition engine, an arc-shaped concave portion is provided which is offset toward the intake valve arrangement side of a piston crown surface, as shown in, for example, Japanese Patent Application Laid-Open No. 9-144543. At the same time, the exhaust valve arrangement is formed with an inclined flat convex portion connected to the edge of the concave portion, and the fuel spray injected from the fuel injection valve toward the concave portion during stratified combustion and the combustion in the intake stroke. In order to achieve both the promotion of air-fuel mixture formation by collision diffusion with the forward tumble flow formed in the chamber and the prevention of unnecessarily large diffusion, and as disclosed in Japanese Patent Application Laid-Open No. 9-209758, The arcuate concave portion on the intake valve arrangement side and the arcuate concave portion on the exhaust valve arrangement side form a side ω-shaped concave portion adjacent to the ridgeline of the central projection on the surface, and are formed in the combustion chamber during stratified combustion. Of fuel spray by forward tumbling flow Such as those to be able to improve the transport properties of the surrounding grayed are known.

[0003]

These are all forward tumble flows formed in the combustion chamber in the intake stroke, that is, the intake air taken in from the intake port is directed from the exhaust valve arrangement side to the piston crown surface. The swirl type of horizontal swirling flow is achieved by transporting the fuel spray injected during the compression stroke during stratified combustion around the ignition plug at the center of the combustion chamber by the vertical swirling flow that is reversed at the spark plug arrangement side. To the concave wall surface provided on the piston crown surface, as compared with the reverse tumble flow type in which the vertical swirling flow is downward from the intake valve arrangement side opposite to the forward tumble flow and reverses on the piston crown surface. This has the effect of suppressing fuel adhesion.

[0004] However, in the former case, the inclined flat convex portion is formed on the side of the piston crown where the exhaust valve is disposed, so that the preservability of the forward tumble flow formed in the combustion chamber during the intake stroke is poor. The forward tumble flow is attenuated by the projections during the compression stroke, and the transportability of the fuel spray around the ignition plug during stratified combustion may be impaired, resulting in unstable combustion.

Further, in the latter, a concave portion having a side surface ω shape is formed in the piston crown surface, and an arc-shaped concave portion is also present on the exhaust valve arrangement side. Even if the transportability of the fuel spray around the ignition plug during combustion can be improved compared to the former, the ω-shaped recess on the side face of the piston crown shows the fuel injection axis of the fuel injection valve and the forward tumble flow in plan view. Since there is no substantially parallel wall, the fuel spray guide function cannot be obtained, it is difficult to keep the fuel near the spark plug, and there is a possibility that stable stratified combustion cannot be performed.

In addition, since the concave portion having the side ω shape is formed in the substantially horizontal piston crown surface, and the central projection portion is formed to protrude larger than the reference surface of the piston crown surface, the fuel injected during stratified combustion is formed. However, the collision with the central projection causes a large amount of fuel to adhere to the wall surface, causing not only the generation of smoke and untwisted HC, but also the large height of the projection when the intake stroke injection is performed during homogeneous combustion. The presence of the portion causes stagnation of the gas flow and makes it difficult to homogenize the air-fuel mixture, which may cause a decrease in output and the generation of untwisted HC and smoke during homogeneous combustion.

Therefore, the present invention can further improve the transportability of the fuel spray around the spark plug by the forward tumble flow, stabilize the stratified combustion, and also produce smoke and untwisted HC caused by fuel wall adhesion. It is intended to provide an in-cylinder injection spark ignition engine capable of suppressing the generation of sparks.

[0008]

According to the first aspect of the present invention, a fuel injection valve for directly injecting fuel into the combustion chamber is provided on a side of the combustion chamber on the side where the intake valve is disposed, and substantially at the center of the combustion chamber. In a direct injection type spark ignition engine in which a spark plug is provided at a position facing the front and a fuel injection is performed during a compression stroke in a state where a forward tumble flow is given to intake air during stratified combustion, a central projection is provided on a piston crown surface. The arcuate concave portion on the intake valve arrangement side and the arcuate concave portion on the exhaust valve arrangement side form a ω-shaped concave portion adjacent to the ridge line, and the arcuate concave portion on the intake valve arrangement side is viewed in a plan view. While the injection valve is extended in the injection axis direction and set to be narrow, the arc-shaped concave portion on the exhaust valve side is extended and set to be wide in the direction orthogonal to the injection axis direction of the fuel injection valve. The ridge of the central projection from the position where the spark plug is It is characterized in that set in a position offset to the exhaust valve arrangement side.

According to a second aspect of the present invention, the height of the central projection of the concave portion having the ω-shaped cross section according to the first aspect is adjusted by changing the height of the arc-shaped concave portion on the intake valve side and the arc-shaped concave portion on the exhaust valve side. In this case, the height is set lower than a straight line connecting the outer edges facing each other with the center protruding portion as the center.

According to the third aspect of the present invention,
The arc-shaped concave portion on the intake valve arrangement side described in (1) is formed deeper than the arc-shaped concave portion on the exhaust valve arrangement side.

According to the invention of claim 4, claims 1 and 2 are provided.
The arc-shaped concave portion on the exhaust valve arrangement side described in (1) is formed deeper than the arc-shaped concave portion on the intake valve arrangement side.

According to a fifth aspect of the present invention, in the first aspect,
The arc-shaped concave portion on the intake valve arrangement side and the arc-shaped concave portion on the exhaust valve arrangement side described in 3 and 4 are formed in a flat rectangular shape, and the outer edges opposed to each other around the central projection of the arc-shaped concave portion are provided on the outer edges. It has a ridge line parallel to the ridge line of the central protrusion, and
It is characterized in that a protruding portion having a height higher than the central protruding portion is formed.

According to the invention of claim 6, claims 1 to 4 are provided.
The arc-shaped concave portion on the exhaust valve arrangement side described in (1) is formed in a plane semicircular shape extending to the vicinity of the periphery of the piston crown surface.

In the invention of claim 7, claims 1 to 4 are provided.
The arc-shaped concave portion on the intake valve arrangement side and the arc-shaped concave portion on the exhaust valve arrangement side are formed in a planar elliptical shape having a major axis in the longitudinal direction.

In the invention of claim 8, claims 1 to 7
In the intake port opened and closed by the intake valve described in (1), a forward tumble reinforcing means for enhancing a forward tumble flow formed in the combustion chamber during the intake stroke during stratified combustion is provided.

According to a ninth aspect of the present invention, the forward tumbling enhancing means according to the eighth aspect shields a substantially lower half of the intake port during stratified combustion and opens the intake port during homogeneous combustion. It is characterized by being.

According to the tenth aspect of the present invention, the forward tumbling enhancing means according to the eighth aspect includes a shutoff valve for fully closing and shutting off the intake port during stratified combustion and opening the intake port during homogeneous combustion. It is characterized by comprising a sub-port opened upstream of the shut-off valve and the other end opened near the intake valve.

In the eleventh aspect of the present invention,
10. The fuel injection valve according to item 10, wherein the engine is stationary.
The spray angle and the mounting angle are set so that the fuel spray injected from the fuel injection valve does not directly hit the ignition plug.

[0019]

According to the first aspect of the present invention, the arcuate concave portion on the intake valve arrangement side and the arcuate concave portion on the exhaust valve arrangement side are adjacent to the piston crown surface with the ridgeline of the central projection as a boundary. In addition to the fact that the forward tumble flow formed in the combustion chamber during the intake stroke is easily preserved by the arc-shaped concave portion on the exhaust valve arrangement side, the central protruding portion is formed. Is offset to the exhaust valve arrangement side from the position of the spark plug, so that the forward tumble flow is swirled in the arcuate recess on the exhaust valve arrangement side, and the arcuate recess on the exhaust valve arrangement side. Is set wide so as not to hinder the swirling of the forward tumble flow, so that the flow force of the forward tumble flow is not attenuated over the latter half of the compression stroke, and the preservability of the forward tumble flow is improved. Can be

At the same time, the arc-shaped concave portion on the intake valve arrangement side is formed narrow and has wall surfaces on both sides, so that the fuel spray injected from the fuel injection valve during the compression stroke is formed. Diffusion in the left-right direction with respect to the axis is suppressed, and the ridgeline of the central projection is offset to the exhaust valve arrangement side and away from the tip of the fuel injection valve. Adhesion can be suppressed as much as possible.

As a result, the collision effect between the fuel spray injected during the compression stroke and the forward tumble flow can be positively performed, and in this collision, the fluid friction can be utilized to the maximum and the fuel spray can be used. The vaporization and the formation of the combustible mixture can be promoted, and the guide action of the central projection allows the combustible mixture to be transported around the ignition plug at the center of the combustion chamber, thereby suppressing diffusion to the surroundings. As a result, stratified combustion can be stabilized, smoke and untwisted HC caused by fuel adhesion to the piston crown surface can be reduced, and deposit accumulation can be prevented. As a result, the combustibility of stratified combustion and the emission characteristics can be improved. And can be realized.

On the other hand, during homogeneous combustion, fuel is injected from the fuel injection valve in the middle of the intake stroke. In this case, too, the conservativeness of the forward tumble flow is enhanced by the concave portion having a ω-shaped cross section on the piston crown surface. The effect of suppressing the adhesion of fuel to the piston crown surface due to the collision with the forward tumble flow is obtained, and the effect of promoting atomization and vaporization of the fuel is obtained. In this case, it is possible to reduce the amount of smoke and untwisted HC and to suppress the accumulation of deposits.
Improvements in combustion efficiency and output can be realized.

According to the invention described in claim 2, according to claim 1
In addition to the effect of the invention, the height of the central projection of the concave portion having a cross section of ω is set to an appropriate height that does not greatly protrude from the piston crown surface, so that fuel spray to the central projection during stratified combustion Can be suppressed as much as possible, and the exhaust properties can be further improved.

In addition, during homogeneous combustion, stagnation of the gas flow due to the presence of the central projection can be avoided, and the homogenization of the mixture can be further improved.

According to the third aspect of the invention, in addition to the effects of the first and second aspects, the arcuate concave portion on the intake valve arrangement side is formed deeper than the arcuate concave portion on the exhaust valve arrangement side. As a result, the distance until the fuel spray reaches the piston crown surface becomes longer, and a liquid film of fuel is less likely to be formed on the piston crown surface.Therefore, the effect of reducing smoke and untwisted HC and preventing deposit accumulation is further improved. Therefore, the stability of stratified combustion and homogeneous combustion can be further improved.

According to the fourth aspect of the invention, in addition to the effects of the first and second aspects, the arc-shaped concave portion on the exhaust valve side is formed deeper than the arc-shaped concave portion on the intake valve side. As a result, the preservability of the forward tumble flow is further enhanced, and it is possible to reliably prevent the fuel spray from diffusing beyond the central projection to the exhaust valve arrangement side during the compression stroke injection, further improving the stability of stratified combustion. On the other hand, during the intake stroke injection, the preservability of the forward tumble flow is further enhanced, so that the homogenization of the fuel is improved, and the stability of the homogeneous combustion can be further improved.

According to the fifth aspect of the present invention, in addition to the effects of the first, third, and fourth aspects, the outer edges of the arc-shaped concave portion on the intake valve side and the arc-shaped concave portion on the exhaust valve side are provided. Is
Protrusions with ridges parallel to the ridges of the central protrusions are provided, so these arc-shaped recesses can be formed to an appropriate depth without changing the compression ratio of the engine, which impairs output. In addition, it is possible to improve the combustibility and the exhaust properties.

Since the ridges of the projections are set parallel to the ridges of the central projection, the movement of the forward tumble flow swirling in the cylinder near these projections is not hindered. .

Further, since the central projection is set lower than each of the projections and set at an appropriate height so as not to protrude greatly from the piston crown surface, the fuel spray collides with the central projection during stratified combustion. In addition, it is possible to prevent stagnation of gas flow due to the presence of the central projection during homogeneous combustion, thereby improving homogenization of the air-fuel mixture.

According to the invention described in claim 6, according to claim 1 of the present invention,
In addition to the effects of the inventions of (1) to (4), since the arc-shaped concave portion on the exhaust valve arrangement side is formed in a plane semicircular shape extending to the vicinity of the periphery of the piston crown surface, the effect of preserving the forward tumble flow can be further enhanced. Thus, it is possible to more effectively improve the combustibility and the exhaust properties.

According to the invention of claim 7, according to claim 1,
In addition to the effects of the present invention, the arc-shaped concave portion on the intake valve side and the arc-shaped concave portion on the exhaust valve side are formed in a plane elliptical shape having a major axis in the longitudinal direction. The forward tumble flow swirling in the arc-shaped concave portion on the arrangement side can be collected around the ignition plug in the center of the combustion chamber, while the fuel spray injected into the arc-shaped concave portion on the intake valve arrangement side can be collected around the ignition plug. Therefore, the diffusion of the fuel spray to the surroundings during stratified combustion can be suppressed, and the transportability of the fuel spray around the spark plug can be further improved.

[0032] According to the invention of claim 8, according to claim 1 of the present invention.
In addition to the effects of the present invention, the forward tumble strengthening means is provided at the intake port, so that the forward tumble flow having a strong flow force can be given to the intake air during the stratified combustion, so that the stratified combustion can be stably performed in a wide operating region. Can be performed, and a reduction in fuel consumption can be realized.

According to the ninth aspect of the present invention, in the eighth aspect,
In addition to the effect of the invention, since a partial shut-off valve that shields a substantially lower half of the intake port is used as the forward tumbling enhancing means, a simple forward flow with a simple configuration can be formed, It can be advantageously obtained in terms of cost and design.

According to the tenth aspect of the present invention, in addition to the effect of the eighth aspect, a shutoff valve for fully closing and shutting off the intake port as forward tumbling enhancing means, and a differential pressure between the upstream and downstream of the shutoff valve are provided. And a subport that injects air from a position near the intake valve, can reliably enhance the forward tumble flow even in a low rotation range where it is difficult to form a forward tumble flow, and realize stable stratified combustion. .

According to the eleventh aspect, in addition to the effects of the first to tenth aspects, the fuel spray angle and the mounting angle of the fuel injection valve are set to optimal angles.
It is possible to perform ideal stratified combustion and homogeneous combustion that can improve the combustibility and the exhaust properties.

[0036]

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

1 and 6, reference numeral 1 denotes a cylinder block, 2 denotes a piston, 3 denotes a cylinder head, and 4 denotes a combustion chamber formed by the cylinder block 1, the piston 2, and the cylinder head 3.

The cylinder head 3 has two intake valves 5,
It has a cross-flow port structure that includes the intake valve 5 and two exhaust valves 6 disposed to face each other, and that takes in air from an intake port 7 on one side and exhausts it from an exhaust port 8 on the other side.

The cylinder head 3 is provided with an ignition plug 9 substantially at the center of the combustion chamber 4, and at the side of the combustion chamber near the intake valve 5, specifically, at two sides of the combustion chamber 4. A fuel injection valve 10 is provided at a position near the opening between the intake ports 7, 7, and fuel is directly injected from the fuel injection valve 10 into the combustion chamber 4.

The intake ports 7, 7 are provided in the vertical swirling flow as the in-cylinder flow formed in the combustion chamber 4 during the intake stroke.
As shown by the arrow A in FIG. 1, the intake air passes through the lower side of the spark plug 9 from the exhaust valve arrangement side to the crown surface of the piston 2, and is reversed at the piston crown surface to the upper ignition plug 9. The flow is formed.

In the intake ports 7, 7, a forward tumble flow A formed in the combustion chamber 4 during the intake stroke during stratified charge combustion is provided.
Is provided.

In the present embodiment, as shown in FIGS.
2 is fully opened at the time of homogenous combustion, and at the time of stratified charge combustion, the lower half of the passage upstream of the branch is shielded so that the circulating air flows through each intake valve 5, 5 as shown by the arrow a in FIG. In addition, as shown in FIGS. 4 and 5, the partial shut-off valve 12 is provided upstream of the branch portion, and is fully opened at the time of homogeneous combustion. A shut-off valve 13 for fully closing and shutting off, and one end opening to the upstream of the shut-off valve 13 and the other end opening to the vicinity of each of the intake valves 5 and 5. As shown by arrows a in FIGS. 4 and 5, a combination of a sub port 14 and a sub port 14 for blowing air toward the upper side of each intake valve 5, 5 can be used.

On the other hand, the central projection 1
An arcuate concave portion 16 on the intake valve arrangement side and an arcuate concave portion 17 on the exhaust valve arrangement side are adjacent to each other to form a concave portion 15 having a ω-shaped cross section with respect to the ridge line 8.

Each of the arcuate concave portions 16 and 17 is formed in a plane rectangular shape, and the arcuate concave portion 16 on the side where the intake valve is disposed is extended long in the direction of the injection axis F0 of the fuel injection valve 10 and is set to be narrow. On the other hand, the arc-shaped concave portion 17 on the exhaust valve arrangement side is extended in the direction orthogonal to the injection axis F0 and is set wide so that the ridge of the central projection 18 is exhausted more than the ignition plug 9 is disposed. It is set at a position offset by α from the valve arrangement side.

According to the structure of the above embodiment, the arcuate recess 16 on the intake valve arrangement side and the arcuate recess 17 on the exhaust valve arrangement side are provided on the crown surface of the piston 2 with the ridgeline of the central projection 18 as a boundary.
Formed a concave portion 15 having an adjacent ω-shaped cross section,
In addition to the fact that the forward tumble flow A formed in the combustion chamber 4 during the intake stroke is easily stored by the arcuate concave portion 17 on the exhaust valve arrangement side, the ridge line of the central projection 18 is located closer to the position of the spark plug 9 than the position of the ignition plug 9. Is also offset to the exhaust valve arrangement side, so that the forward tumble flow A is swirled in the arcuate concave portion 17 on the exhaust valve arrangement side, and the arcuate concave portion 17 on the exhaust valve arrangement side is widened. Since it is set so as not to hinder the swirling of the forward tumble flow A, the flow force of the forward tumble flow A is not attenuated over the latter half of the compression stroke, and the preservability of the forward tumble flow A is improved. Can be

At the same time, since the arc-shaped concave portion 16 on the intake valve arrangement side is formed narrow and has wall surfaces 16a on both sides thereof, the fuel injected from the fuel injection valve 10 during the compression stroke. The diffusion of the spray F in the left-right direction with respect to the injection axis F0 is suppressed, and the ridgeline of the central projection 18 is offset by α from the ignition plug 9 at the center of the combustion chamber toward the exhaust valve arrangement side. Since the fuel spray F is away from the tip, collision and adhesion of the fuel spray F to the central projection 18 can be suppressed as much as possible.

As a result, the collision effect between the fuel spray F injected during the compression stroke and the forward tumble flow A can be positively performed. The vaporization of the spray F and the formation of a combustible mixture can be promoted, and the transport of the combustible mixture around the ignition plug 9 at the center of the combustion chamber is favorably performed by the guide action of the central projection 18 to the surroundings. Can stabilize stratified combustion, reduce smoke and untwisted HC caused by fuel adhesion to the piston crown surface, and prevent deposits from accumulating. The improvement and the improvement of the exhaust property can be realized.

FIGS. 7 and 8 schematically illustrate the motion of the air-fuel mixture during the above-described stratified combustion. In the stratified combustion operation region, when the engine speed is high, the amount of intake air is large. As shown in (a), the forward tumble flow A that largely swirls in the combustion chamber 4 is likely to remain relatively until the latter half of the compression stroke, and the fuel spray F injected from the fuel injection valve 10 during the compression stroke immediately follows the forward flow. The fuel is pushed up above the combustion chamber 4 by the tumble flow A, and is transported in the direction of the spark plug 2 while being vaporized, whereby stratification is performed.

As the piston 2 rises, the forward tumble flow A which turns largely as shown in FIG. 7 (b) turns in the arcuate concave portion 17 on the exhaust valve arrangement side as shown in FIG. F is suppressed by the forward tumble flow A, the diffusion toward the exhaust valve arrangement side is suppressed, and the fuel F is reliably transported around the spark plug 9.

On the other hand, when the engine speed is low even in the stratified charge combustion operation range, the amount of intake air is small, and as shown in FIG. 8 (a), the forward tumble flow A swirling in the combustion chamber 4 generates the exhaust valve during the compression stroke. The swivel is concentrated on the arcuate recess 17 on the arrangement side. Therefore, the fuel spray F injected from the fuel injection valve 10 during the compression stroke is not deflected upward of the combustion chamber 4 immediately after the injection, but as shown in FIG. Due to the guiding action of the arcuate recess 16 and the central projection 18 and the forward tumble flow A, the fuel is transported around the ignition plug 9 and its diffusion to the exhaust valve arrangement side is suppressed. Transportability is enhanced.

Therefore, even if the height of the ridgeline of the central projection 18 is not so large as to protrude greatly from the piston crown surface, the diffusion of the fuel spray F toward the exhaust valve arrangement side during stratified combustion can be suppressed. It is possible to avoid deterioration of exhaust properties and decrease in output due to fuel attachment to the central projection 18.

In this embodiment, since the forward tumble strengthening means 11 for strengthening the forward tumble flow A during stratified charge combustion is provided in the intake port 7, a strong flow force is exerted on the intake air during stratified charge combustion. The forward tumble flow A can be provided, stable stratified combustion can be performed in a wide operation range, and a reduction in fuel consumption can be realized.

When the partial shut-off valve 12 is used as the forward tumbling reinforcing means 11 as described above, a strong forward tumbling flow A can be formed with a simple structure, and the cost and design can be reduced. Can be advantageously obtained.

When the forward tumble strengthening means 11 is a combination of the shut-off valve 13 and the subport 14 shown in FIGS. , The forward tumble flow A can be surely strengthened and stable stratified combustion can be performed.

On the other hand, during homogeneous combustion, fuel is injected from the fuel injection valve 10 in the middle of the intake stroke. In this case also, the preservation of the forward tumble flow is enhanced by the concave portion 15 having a ω-shaped cross section of the piston crown. The effect of suppressing fuel adhesion to the piston crown due to the collision between the fuel spray F and the forward tumble flow A is obtained, and the effect of atomizing and vaporizing the fuel is obtained, so that the combustible mixture is substantially uniform in the combustion chamber 4. Therefore, homogeneous combustion can be performed favorably, so that also in this case, it is possible to reduce smoke and untwisted HC, suppress the accumulation of deposits, and improve combustion efficiency and output.

FIGS. 9 to 12 show different embodiments of the present invention. In each of these embodiments, the height of the ridge line of the central projection 18 in the structure of the first embodiment shown in FIG. , Is set low so as not to protrude from the piston crown.

In other words, the third embodiment shown in FIG. 9 will be described as an example.
6 and the central projection 18 of the arc-shaped recess 17 on the exhaust valve arrangement side.
A straight line L connecting the outer edges S • E, S • E facing each other
It is set lower than.

Accordingly, the recess 15 having the ω-shaped cross section is thus obtained.
By setting the height of the central projection 18 to an appropriate height that does not greatly protrude from the crown surface of the piston 2, it is possible to prevent the fuel spray F from adhering to the central projection 18 during stratified combustion by collision. The exhaust characteristics can be further improved as compared with the first embodiment.

Here, in the fourth embodiment shown in FIG. 10, the depth D ₁ of the arc-shaped concave portion 16 on the intake valve arrangement side is made larger than the depth D ₂ of the arc-shaped concave portion 17 on the exhaust valve arrangement side. Is also deeply formed.

Therefore, in the case of the fourth embodiment, the distance required for the fuel spray F injected from the fuel injection valve 10 to reach the piston crown becomes longer, and a liquid film of fuel is less likely to be formed on the piston crown. Therefore, the effects of reducing smoke and untwisted HC and preventing the deposition of deposits can be further enhanced, and the stability of stratified combustion and homogeneous combustion can be further improved.

In the fifth embodiment shown in FIG. 11, contrary to the embodiment shown in FIG.
The depth D ₂ of the arcuate recess 16 on the intake valve arrangement side.
It is formed deeper than ₁ .

Therefore, in the fifth embodiment, the preservability of the forward tumble flow A is further enhanced, and the fuel spray F is surely diffused to the exhaust valve arrangement side beyond the central projection 18 during the compression stroke injection. Can be prevented, and the stability of stratified combustion can be further improved. On the other hand, during the intake stroke injection, the preservation of the forward tumble flow A is enhanced, so that the homogenization of the fuel is improved and the stability of the homogeneous combustion is further improved. can do.

In the sixth embodiment shown in FIG. 12, the outer edges S, SE, SE of the arcuate recess 16 on the intake valve side and the arcuate recess 17 on the exhaust valve side are: Protrusions 20, 20 having ridges parallel to the ridge of the central protrusion 18 and having a height higher than the central protrusion 18 are formed.

Therefore, in the case of the sixth embodiment, the arcuate recess 16 on the intake side and the arcuate recess 17 on the exhaust valve arrangement side can be appropriately formed without changing the compression ratio of the engine by projecting the projections 20, 20. The fuel cell can be formed deeper to the depth, and the improvement of the combustibility and the improvement of the exhaust property can be realized without impairing the output.

FIG. 13 shows a seventh embodiment of the present invention. In this embodiment, the arc-shaped concave portion 17 on the exhaust valve arrangement side is formed into a semicircular planar shape extending to the vicinity of the periphery of the piston crown. It is formed.

As described above, the arc-shaped concave portion 17 on the exhaust valve arrangement side
Is enlarged to a plane semicircular shape, so that the forward tumble flow A
Is further enhanced, and the improvement of combustibility and the improvement of exhaust properties can be more effectively performed.

FIG. 14 shows an eighth embodiment of the present invention. In this embodiment, the arc-shaped concave portion 16 on the intake valve side and the arc-shaped concave portion 17 on the exhaust valve side are respectively connected to the longitudinal direction. It is formed in a plane elliptical shape having a major axis in the direction.

In this case, the central projection 18 is set so that its ridge line is on the elliptical outline of the arcuate concave portion 17 on the exhaust valve arrangement side.

As described above, the arcuate concave portion 16 on the intake valve arrangement side
By forming the arc-shaped recess 17 on the exhaust valve arrangement side in a plane elliptical shape, the arc-shaped recess 17 on the exhaust valve arrangement side burns the forward tumble flow A swirling in the arc-shaped recess 17 along the elliptical shape. While the fuel spray F can be collected around the ignition plug 9 at the center of the chamber, the fuel spray F injected toward the arc-shaped recess 16 is collected around the ignition plug 9 along the elliptical shape in the arc-shaped recess 16 on the intake valve arrangement side. Therefore, the effect of preventing diffusion around the fuel spray F during stratified combustion can be further enhanced, and transportability of the fuel spray F around the spark plug 9 can be further improved.

Here, in any of the above embodiments,
It is important that the fuel injection valve 10 be set to a spray angle and a mounting angle such that the fuel spray F injected from the fuel injection valve 10 does not directly hit the ignition plug 9 when the engine is stationary, thereby improving the flammability. In addition, ideal stratified combustion and homogeneous combustion that can improve the exhaust characteristics can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional explanatory view schematically showing a first embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view illustrating the movement of the intake air flow by the forward tumbling enhancing means according to the first embodiment of the present invention.

FIG. 3 is a schematic plan view of FIG. 2;

FIG. 4 is a schematic sectional explanatory view showing a forward tumbling reinforcing means according to a second embodiment of the present invention.

FIG. 5 is a schematic plan view of FIG. 4;

FIG. 6 is an explanatory plan view showing a structure of a piston crown surface in the embodiment shown in FIG. 1;

FIG. 7 is a sectional explanatory view schematically showing a stratified combustion state of the embodiment shown in FIG. 1 at the time of high engine speed.

FIG. 8 is a sectional explanatory view schematically showing a stratified combustion state of the embodiment shown in FIG. 1 during low engine speed.

FIG. 9 is a schematic sectional explanatory view showing a third embodiment of the present invention.

FIG. 10 is a schematic sectional explanatory view showing a fourth embodiment of the present invention.

FIG. 11 is a schematic sectional explanatory view showing a fifth embodiment of the present invention.

FIG. 12 is a schematic sectional explanatory view showing a sixth embodiment of the present invention.

FIG. 13 is an explanatory plan view showing a structure of a piston crown surface according to a seventh embodiment of the present invention.

FIG. 14 is an explanatory plan view showing a structure of a piston crown surface according to an eighth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Piston 3 Cylinder head 4 Combustion chamber 5 Intake valve 6 Exhaust valve 7 Intake port 8 Exhaust port 9 Ignition plug 10 Fuel injection valve 11 Forward tumble strengthening means 12 Partial shutoff valve 13 Shutoff valve 14 Subport 15 Concave part with ω-shaped section 16 Arc-shaped concave portion on the side where the intake valve is arranged 17 Arc-shaped concave portion on the side where the exhaust valve is arranged 18 Central projection A Forward tumble flow F Fuel spray SE Outer edge of the recess F0 Injection axis

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 3/26 F02F 3/26 A

Claims (11)

[Claims] A fuel injection valve for directly injecting fuel into a combustion chamber is provided on a side portion of the combustion chamber on a side where an intake valve is disposed, and a spark plug is provided at a position substantially facing the center of the combustion chamber. In a direct injection type spark ignition engine in which fuel is injected during the compression stroke in a state where a forward tumble flow is provided, an arc-shaped concave portion on the intake valve arrangement side with a ridge line of a central projection on a piston crown surface is provided. The arc-shaped concave portion on the exhaust valve arrangement side forms a concave portion having a cross section ω shape adjacent to the arc-shaped concave portion, and the arc-shaped concave portion on the intake valve arrangement side extends long in the injection axis direction of the fuel injection valve in plan view and is narrow. On the other hand, the arc-shaped concave portion on the exhaust valve arrangement side is extended to extend in a direction orthogonal to the injection axis direction of the fuel injection valve so as to be wide, and the ridge line of the central projection is set to the ignition plug arrangement position. To a position offset to the exhaust valve side Cylinder injection type spark ignition engine, characterized in that. 2. The height of the central protruding portion of the concave portion having the ω-shaped cross section is determined by adjusting the outer edges of the arc-shaped concave portion on the intake valve side and the arc-shaped concave portion on the exhaust valve side facing each other around the central protruding portion. 2. The in-cylinder injection spark ignition engine according to claim 1, wherein the engine is set to be lower than a straight line connecting the engine. 3. The in-cylinder injection spark ignition engine according to claim 1, wherein the arc-shaped concave portion on the intake valve side is formed deeper than the arc-shaped concave portion on the exhaust valve side. 4. The in-cylinder injection spark ignition engine according to claim 1, wherein the arc-shaped concave portion on the exhaust valve arrangement side is formed deeper than the arc-shaped concave portion on the intake valve arrangement side. 5. An arcuate concave portion on the intake valve arrangement side and an arcuate concave portion on the exhaust valve arrangement side are formed in a planar rectangular shape, and each of the outer edges opposed to each other around a central projection of the arcuate concave portion is provided with the center. It has a ridge line parallel to the ridge line of the protrusion, and
5. The in-cylinder injection spark ignition engine according to claim 1, wherein a projection that is higher than the central projection is formed. 6. The in-cylinder injection type according to claim 1, wherein the arc-shaped concave portion on the exhaust valve arrangement side is formed in a plane semi-circular shape extending to near the peripheral portion of the piston crown surface. Spark ignition engine. 7. An arcuate concave portion on the intake valve side and an arcuate concave portion on the exhaust valve side are each formed in a plane elliptical shape having a major axis in the longitudinal direction.
5. The in-cylinder injection spark ignition engine according to any one of 4. 8. A forward tumbling enhancing means for enhancing forward tumbling flow formed in a combustion chamber during an intake stroke during stratified combustion in an intake port opened and closed by an intake valve. 8. The in-cylinder injection spark ignition engine according to any one of 7 above. 9. The forward tumbling enhancing means is a partial shut-off valve that shields a substantially lower half of the intake port during stratified combustion and opens the intake port during homogeneous combustion.
2. The in-cylinder injection spark ignition engine according to claim 1. 10. A forward tumbling enhancing means for completely closing and shutting off an intake port at the time of stratified combustion and opening the intake port at the time of homogeneous combustion; 9. The in-cylinder injection spark ignition engine according to claim 8, wherein the sub-port is opened in the vicinity. 11. The fuel injection valve is set at a spray angle and a mounting angle such that the fuel spray injected from the fuel injection valve does not directly hit the spark plug when the engine is stationary. In-cylinder injection spark ignition engine according to any one of the above.