JP2003049652A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form superior homogeneous air-fuel mixture in a cylinder injection type spark ignition internal combustion engine forming a tumble flow, at least, lowering along an exhaust port of a cylinder bore and rising via a piston top surface in an intake stroke. SOLUTION: This cylinder injection type spark ignition internal combustion engine is provided with the intake port 5 and the exhaust port 7 connected to each other in the upper part of a cylinder and, at least, performs the homogeneous combustion. The tumble flow T1 lowering along the exhaust port side of the cylinder bore and rising via the piston top surface is produced by intake air introduced from the intake port. A fuel injection valve 2 is disposed in the intake port side in the upper part of the cylinder and injects fuel as a tapered-shape spray 10 and the tapered-shape spray is injected toward the piston top surface side of the air flow in the homogeneous combustion without interfering the air flow heading from the intake port to the exhaust port side of the cylinder bore for producing the tumble flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder injection type spark ignition internal combustion engine.

[0002]

2. Description of the Related Art An in-cylinder injection spark ignition internal combustion engine is known in which fuel is directly injected into a cylinder in order to reliably supply a required amount of fuel into the cylinder.

In such an in-cylinder injection type spark ignition internal combustion engine, homogeneous combustion is carried out in which fuel is injected in the intake stroke to form a homogeneous mixture in the cylinder, and the homogeneous mixture is ignited and burned. In order to achieve good homogeneous combustion, it is necessary to mix the injected fuel sufficiently with the intake air to form a good homogeneous mixture.

In Japanese Patent Laid-Open No. 11-141338, when intake air is introduced into the cylinder from an intake port connected to the upper part of the cylinder in the intake stroke, the intake air is introduced from the exhaust port side of the in-cylinder opening of the intake port. Is lowered along the exhaust port side of the cylinder bore, and the intake air introduced from the side opposite to the exhaust port of the cylinder opening of the intake port is lowered along the intake port side of the cylinder bore, causing these airflows to collide with the top surface of the piston. It is disclosed that an omega (ω) -shaped tumble flow is generated in the cylinder by deflecting it toward the upper part of the cylinder. By using the omega-shaped tumble flow generated in the cylinder during the intake stroke,
It is said that the injected fuel is sufficiently mixed with the intake air to form a good homogeneous mixture.

[0005]

However, even if an omega-shaped tumble flow is generated in the cylinder during the intake stroke, the fuel that is not sufficiently atomized by simply injecting the fuel into the cylinder is a tumble flow. However, it is not possible to form a good homogeneous air-fuel mixture.

Therefore, an object of the present invention is to provide an in-cylinder injection spark ignition internal combustion in which a tumble flow that descends along at least the exhaust port side of the cylinder bore and rises through the piston top surface is generated in the cylinder during the intake stroke. In the engine, it is possible to form a good homogeneous mixture.

[0007]

In a cylinder injection type spark ignition internal combustion engine according to a first aspect of the present invention, an intake port and an exhaust port are connected to an upper portion of a cylinder, and a fuel for injecting fuel into the cylinder is injected. In a cylinder injection type spark ignition internal combustion engine equipped with an injection valve for performing at least homogeneous combustion, the intake air introduced into the cylinder from the intake port descends along the exhaust port side of the cylinder bore to pass through the piston top surface. A rising tumble flow is generated, the fuel injection valve is arranged on the intake port side of the upper part of the cylinder and injects fuel as a divergent spray, and the divergent spray is at the time of the homogeneous combustion, To generate the tumble flow, from the air intake port toward the exhaust port side of the cylinder bore, the air flow is directed toward the piston top surface side without interfering with the air flow. Characterized in that it is injected.

A cylinder injection type spark ignition internal combustion engine according to a second aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the first aspect, wherein an exhaust port at an in-cylinder opening of the intake port is provided. The intake air introduced into the cylinder through the side generates the tumble flow, and the intake air introduced into the cylinder through the side opposite to the exhaust port at the opening in the cylinder descends along the intake port side of the cylinder bore. A divergent spray that generates a reverse tumble flow that rises through the piston top surface and is injected from the fuel injection valve passes between the cylinder inner opening and the piston top surface, and the cylinder inner opening is formed. The non-exhaust port side of the non-passage area of the non-passage-port side of the piston that does not pass the divergent spray in plan view and the pass range portion in the plan view that faces the piston top surface. The reverse tumble flow is generated by the intake air introduced into the cylinder through the non-passage range portion, while the reverse tumble flow is generated by the intake air introduced into the cylinder through the passage range portion. It is characterized in that a reverse tumble flow suppressing unit is provided to prevent the reverse tumble flow from being generated.

A cylinder injection type spark ignition internal combustion engine according to a third aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the first aspect, wherein the fuel injection valves do not interfere with each other. It is characterized in that the two divergent sprays are injected toward the piston top surface side from the airflow without interfering with the airflow.

A cylinder injection type spark ignition internal combustion engine according to a fourth aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the third aspect, wherein an exhaust port at an in-cylinder opening of the intake port is provided. The intake air introduced into the cylinder through the side generates the tumble flow, and the intake air introduced into the cylinder through the side opposite to the exhaust port at the opening in the cylinder descends along the intake port side of the cylinder bore. A reverse tumble flow that rises through the piston top surface is generated, and the two sprays having the pre-spread shape injected from the fuel injection valve pass between the in-cylinder opening and the piston top surface, and The anti-exhaust port side of the in-cylinder opening has a passage range portion through which the two divergent sprays pass in the plan view facing the piston top surface and the two divergent sprays in the plan view. Is divided into a non-passing range portion that does not pass, and the reverse tumble flow is generated by the intake air introduced into the cylinder through the non-passing range portion, but is introduced into the cylinder through the passing range portion. It is characterized in that a reverse tumble flow suppressing means is provided for preventing the reverse tumble flow from being generated depending on the intake air to be taken.

A cylinder injection type spark ignition internal combustion engine according to a fifth aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the fourth aspect, wherein one of the two flared sprays is formed. Located on the upper side of the cylinder, the other of the two divergent sprays is located on the piston top surface side, and the one divergent spray has a higher penetration force than the other divergent spray. It is characterized by having.

A cylinder injection type spark ignition internal combustion engine according to a sixth aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the fifth aspect, wherein the one of the sprays having the flared shape is Compared to the other spray with a divergent shape, the divergence angle is smaller and the penetration force is higher.

A cylinder injection type spark ignition internal combustion engine according to a seventh aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to the fifth or sixth aspect, wherein It is characterized in that the tumble flow is injected toward the vicinity of the swirl center, and the other spray having the spread shape is injected toward the vicinity of the swirl center of the reverse tumble flow.

The cylinder injection type spark ignition internal combustion engine according to claim 8 of the present invention is the cylinder injection type spark ignition internal combustion engine according to claim 2 or 4, wherein the intake port is opened in the cylinder. The reverse tumble flow suppressing means has a curved portion on the upstream side, and the reverse tumble flow suppressing means forms a part of the convex corner portion of the curved portion to be sharp and passes along the intake port wall surface on the downstream side of the curved portion. It is characterized by reducing the amount of intake air introduced into the cylinder through the range portion.

A cylinder injection type spark ignition internal combustion engine according to a ninth aspect of the present invention is the cylinder injection type spark ignition internal combustion engine according to any one of the first to eighth aspects, wherein the air flow is the exhaust gas. The main inclination angle of the intake port with respect to the horizontal direction with respect to the piston axis and the main wall of the cylinder with respect to the horizontal direction so that the port advances along the exhaust port side of the cylinder upper wall where the opening in the cylinder is provided. It is characterized in that the relationship with the inclination angle on the exhaust port side is selected.

[0016]

1 is a schematic vertical sectional view of a cylinder in a cylinder injection type spark ignition internal combustion engine according to a first embodiment of the present invention in the latter half of a compression stroke, and FIG. 2 is a plan view of a piston shown in FIG. is there. In these figures, reference numeral 1 is a spark plug arranged substantially in the center of the upper portion of the cylinder, and 2 is a fuel injection valve for directly injecting fuel into the cylinder from around the upper portion of the cylinder. Further, 3 is a piston, and a concave cavity 4 is formed on the top surface thereof. Reference numeral 5 is an intake port connected to the upper portion of the cylinder, and 6 is an intake valve that opens and closes the opening of the intake port 5 in the cylinder. 7 is an exhaust port connected to the upper part of the cylinder. Reference numeral 8 is an exhaust valve that opens and closes the opening of the exhaust port 7 in the cylinder. The fuel injection valve 2 is arranged on the intake port side where the temperature becomes relatively low due to the intake flow in the cylinder in order to prevent fuel vapor.

Further, the fuel injection valve 2 has slit-shaped injection holes and injects the fuel in a thin fan shape.
In order to perform the stratified charge combustion, as shown in FIG. 1, fuel is injected into the cavity 4 formed on the top surface of the piston 3 in the latter half of the compression stroke. Immediately after injection, the fuel 10 is in a liquid state, but when traveling along the bottom wall 4a of the cavity 4 and spreading in the width direction, heat is absorbed from a wide area of the bottom wall 4a, so that the fuel 10 is easily vaporized. The fuel thus vaporized is deflected upward by the opposing side wall 4b.

As shown in FIG. 2, the opposed side wall 4b has an arc shape in plan view. As a result, the fuel advancing on the bottom wall 4a of the cavity 4 and vaporizing is
Due to the arc shape of the opposing side wall 4b, they gather together in the central portion and form a lump of combustible air-fuel mixture in the vicinity of the spark plug 1. Thus, stratified combustion can be realized by igniting and burning the combustible mixture.

As described above, the cylinder injection type spark ignition internal combustion engine of this embodiment uses the fuel injection valve having the slit-shaped injection hole and the cavity 4 of the specific shape to ignite the spark plug without using the air flow. A relatively good combustible mixture can be formed in the vicinity of 1. In stratified combustion, a combustible air-fuel mixture is formed only in the vicinity of the spark plug 1 so that a lean air-fuel mixture in the entire cylinder can be combusted, so that fuel consumption can be favorably reduced.

However, in the stratified charge combustion, as described above, it is necessary to inject the fuel into the cavity 4 on the top surface of the piston, and the fuel can be injected only in the limited piston range in the latter half of the compression stroke. As a result, in a cylinder injection type spark ignition internal combustion engine, it is common to carry out homogeneous combustion in which fuel is injected in an intake stroke to form a homogeneous mixture at the time of high engine load in which a large amount of fuel is required. Homogeneous combustion in a direct-injection spark ignition internal combustion engine allows fuel to be reliably supplied to the cylinder in the required amount. It is not required to inject more fuel than necessary, which is effective in reducing the fuel consumption rate.

FIG. 3 is a schematic vertical sectional view in the cylinder of the cylinder injection type spark ignition internal combustion engine of this embodiment in the middle of the intake stroke. The fuel injection valve 2 injects fuel in the intake stroke for homogeneous combustion. It is being carried out. When the intake valve 6 is opened in the intake stroke, the intake air introduced into the cylinder through the exhaust port side of the in-cylinder opening 51 of the intake port 5 descends along the exhaust port side of the cylinder bore and the piston top. It is easy to generate the tumble flow T1 that rises through the surface. On the other hand, the intake air introduced into the cylinder through the anti-exhaust port side of the in-cylinder opening 51 of the intake port 5 descends along the intake port side of the cylinder bore and rises through the piston top surface T2. Is easy to generate. In this way, the tumble flow T1 and the reverse tumble flow T2 collide with each other on the top surface of the piston and ascend, whereby the tumble flow T1 and the reverse tumble flow T2 are perpendicular to the vertical plane between the intake port and the exhaust port parallel to the piston axis as shown in FIG. When viewed in a vertical section, an omega (ω) -shaped airflow is generated in the cylinder.

As shown in FIG. 4, which is a schematic plan view of the upper portion of the cylinder facing the top surface of the piston, two in-cylinder openings 51 are formed in parallel with the piston axis to facilitate understanding of the invention. As described above, the virtual plane A is divided into two parts, that is, the exhaust port side 51a and the non-exhaust port side 51b, which are substantially equal to each other.

In the past, in homogeneous combustion, in order to form a good homogeneous mixture, it was preferable to make the fuel spray impinge on the air flow immediately after injection. However, in particular, in the case of the divergent shape spray such as the substantially fan-shaped spray in the present embodiment, despite the fact that the atomization and the vaporization of the fuel are promoted during the flight in the cylinder by the inertial force of itself, When the fuel collides with the air flow immediately after injection, the fuel only travels in the cylinder without being atomized and vaporized, and the relatively large granular liquid fuel can be distributed throughout the cylinder, but these are It cannot be fully vaporized by ignition. Thus, even if the fuel spray collides with the air flow in the cylinder immediately after the injection, a good homogeneous mixture cannot be formed as intended.

In the present embodiment, the fuel injection valve 2 is a cylinder in which the fuel flows from the intake port 5 toward the exhaust port side of the cylinder bore to generate the tumble flow T1, that is, before it descends along the exhaust port side of the cylinder bore. The substantially fan-shaped spray 10 is jetted obliquely downward from the airflow toward the piston top surface side without interfering with the airflow traveling along the upper wall. Substantially fan-shaped spray 10
The detailed injection direction of is such that the width direction of the substantially fan-shaped spray 10, that is, the direction of development into the fan shape is not parallel to the vertical plane parallel to the piston axis, and preferably,
As shown in FIG. 3, the width direction of the substantially fan-shaped spray 10 is made parallel to the horizontal plane perpendicular to the piston axis so that only the thickness of the substantially fan-shaped spray can be seen in the specific vertical section. There is. Due to such an injection direction, the substantially fan-shaped spray 10 does not spread much in the vertical direction in the cylinder, and it becomes difficult for the substantially fan-shaped spray 10 to interfere with the air flow that advances in the vertical direction along the cylinder bore.

The thus-sprayed substantially fan-shaped spray flies in the cylinder while spreading in a fan shape by its penetration force without interfering with the air flow, and atomization and vaporization are promoted,
When the penetrating force is sufficiently lost, it is agitated by the omega-shaped air current rising through the top surface of the piston and distributed throughout the cylinder. In this way, it becomes possible to form a good homogeneous mixture of vaporized fuel during the compression stroke until ignition.

FIG. 3 shows the middle of the intake stroke, and the tumble flow T1 and the reverse tumble flow T2 are shown as if they are rising at this time via the top surface of the piston. However, this is for facilitating the understanding of the description of the tumble flow and the reverse tumble flow described above, and in practice, the air flow that generates the tumble flow and the reverse tumble flow is at least in the middle of the intake stroke until the cylinder bore. Along the piston top surface until the end of the intake stroke or the beginning of the compression stroke. Thereby,
In FIG. 3, the injected substantially fan-shaped spray 10 is illustrated so as to interfere with the reverse tumble flow in the middle of the intake stroke even if it does not interfere with the tumble flow. Up to the above, it does not interfere with the reverse tumble flow, and during this period, it is possible to sufficiently atomize and vaporize.

The fuel injected in the early stage of the intake stroke enters into the cavity on the top surface of the piston in the same manner as the fuel injected in the latter half of the compression stroke during stratified charge combustion. All of the injected fuel at this time does not remain in the cavity because it is directed to the vicinity of the plug. Part of the injected fuel that remains in the cavity is vaporized by ignition in the cavity by sufficient time and heat received from the cavity to form a homogeneous mixture in the cavity, and the fuel that reaches the vicinity of the spark plug is It has vaporized to some extent at the time of arrival, and if it is agitated by the omega-shaped air flow in the compression stroke, it can be completely vaporized by ignition.

The divergent shape spray increases the chances that fuel particles separate from each other during flight in the cylinder due to the penetration force and contact the intake air in the cylinder, and at the same time, the fuel particles are introduced into the intake air during flight. Since the atomization and the vaporization are promoted by the friction, the injected fuel can be remarkably vaporized by flying in the cylinder without coming into contact with the air flow. This embodiment utilizes this to promote atomization of the injected fuel,
The fuel atomized sufficiently is agitated by the air flow in the cylinder from the end of the intake stroke or the beginning of the compression stroke when the penetration force is weakened. In the present embodiment, as the tip spread spray, a thin fan-shaped spray is used,
This fuel spray not only increases the chances of each fuel grain coming into contact with the intake air in the cylinder during flight, but also can enhance the penetration force of each fuel grain. However, of course, the invention is not limited to the use of this substantially fan-shaped spray, for example a conical fuel spray is also possible.

By the way, when only the tumble flow is generated in the cylinder during the intake stroke, the fuel spray may be injected so as not to interfere with the tumble flow, but the agitation of the injected fuel in the compression stroke should be good. Therefore, when a reverse tumble flow is also generated in the cylinder, it is necessary to inject the fuel spray so as not to interfere with the reverse tumble flow. In the present embodiment, the intake air introduced into the cylinder via the anti-exhaust port side 51b in the in-cylinder opening 51 of the intake port 5 is adapted to generate a reverse tumble flow and is injected from the fuel injection valve 2. The divergent spray is designed to pass between the in-cylinder opening 51 of the intake port 5 and the piston top surface. Thus, if the cylinder opening 51
If all the intake air introduced into the cylinder through the anti-exhaust port side 51b of the cylinder heads toward the intake port side of the cylinder bore so as to generate a reverse tumble flow, the injected fuel will interfere with this air flow. You will not be able to obtain the full effect.

In this embodiment, the reverse tumble flow suppressing means as described below is provided so that the air flow for generating the reverse tumble flow and the injected fuel do not interfere with each other. In the present embodiment, the intake port 5 has a curved portion 52 immediately upstream of the in-cylinder opening 51, as shown in FIG. Since the length from the curved portion 52 to the in-cylinder opening 51 is relatively short, when the intake valve 6 is opened in the intake stroke, a portion of the intake air passing through the intake port 5 is affected by the curved portion 51. In the direction of the main inclination angle TH1 with respect to the horizontal direction with respect to the piston axis of the intake port 5,
It is introduced into the cylinder through the exhaust port side 51a of the in-cylinder opening 51 and produces a tumble flow T1.

On the other hand, the remaining part of the intake air that passes through the intake port 5 is bent by the curved portion 51 and the main inclination angle T of the intake port is increased.
It is deflected from H1 and introduced into the cylinder through the side 51b opposite to the exhaust port of the in-cylinder opening 51 to generate the reverse tumble flow T2. In the present embodiment, as shown in FIG. 4, the non-exhaust port side 5 of the in-cylinder opening 51 of the intake port 5 is
1b is divided into a passing range portion through which the divergent spray 10 passes and a non-passing range portion through which the divergent spray 10 does not pass in a plan view facing the top surface of the piston. The intake air supplied into the cylinder through the in-cylinder opening 51 of the intake port 5 is mainly due to the presence of the intake valve 6
1 will be passed around. As a result, paying attention only to the periphery of the in-cylinder opening 51, the curved portion 52 of the intake port 5 is divided into a passage range portion in the periphery of the in-cylinder opening 51 and a non-passage range portion in the periphery of the in-cylinder opening 51. Considered separately, the curved portion 52 is divided into a first region R1 that affects the intake air supply to the non-passage range part and a second region R2 that affects the intake air supply to the passage range part.

In the first region R1, the shape of the convex corner portion of the curved portion 52 is a smooth arc shape as shown in FIG. 6 as a PP enlarged cross section. As a result, the intake air that advances in the intake port 5 along the intake port 5 with the main inclination angle TH1 is deflected along the convex corner portion in the first region R1 of the curved portion 52, and the intake air on the downstream side of the curved portion 52 is deflected. Passes through the non-passage range portion of the in-cylinder opening 51 along the intake port,
The air flow is toward the intake port side of the cylinder bore to generate the reverse tumble flow T2. However, fuel spray does not exist below the non-passage range portion of the in-cylinder opening 51 (piston top surface side), and this air flow and fuel spray do not interfere.

On the other hand, in the second region R2, the curved portion 52
The shape of the convex corners is formed as a sharp edge as shown in FIG. 5 as a QQ enlarged cross section. As a result, the intake air that advances in the intake port 5 along the main inclination angle TH1 is mainly separated at the convex corner portion in the second region R2 of the curved portion 52 and is deflected along the convex corner portion. In this case, the main inclination angle TH1 is maintained and the gas is introduced into the cylinder. Thus, there is almost no airflow that passes through the passage range portion of the in-cylinder opening 51 toward the intake port side of the cylinder bore, and is below the passage range portion (piston top surface side).
The fuel spray present in the air has almost no interference with the air flow.

Thus, in the present embodiment, the divergent substantially fan-shaped spray injected from the fuel injection valve 2 does not interfere with the air flow and is sufficiently atomized until it is sufficiently atomized by the penetration force. From the final stage of the intake stroke or the early stage of the compression stroke, the omega-shaped air flow composed of the tumble flow and the reverse tumble flow is sufficiently stirred in the cylinder to form a good homogeneous mixture.

By the way, in the connecting region B between the cylinder upper wall where the in-cylinder opening 7a of the exhaust port 7 is located and the exhaust port side of the cylinder bore shown in FIG. 3, the tumble flow does not pass and the intake air stagnates and the homogeneous mixture is formed. Difficult to form. In order to allow the tumble flow to pass through this connection region B, the inclination angle TH2 of the upper wall of the cylinder on the exhaust port side with respect to the horizontal direction with respect to the piston axis is brought close to the main inclination angle TH1 of the intake port 5, preferably the same. Just do it. As a result, the intake air introduced into the cylinder from the intake port 5 at the main inclination angle TH1 proceeds along the upper wall of the cylinder on the exhaust port side, and the tumble flow passes through the connection region B described above. Become.

FIG. 7 is a schematic vertical sectional view in the cylinder of the cylinder injection type spark ignition internal combustion engine according to the second embodiment of the present invention in the middle of the intake stroke, and FIG. 2 is a plan view of the piston in FIG. Only the differences from the first embodiment will be described below. In the cylinder injection type spark ignition internal combustion engine of the present embodiment, the fuel injection valve 2'includes two substantially fan-shaped sprays 10a, 1
0b is injected. Further, a shallow recess 4'is formed on the entire top surface of the piston 3'excluding the peripheral portion, and the cavity as in the first embodiment is not provided. The recess 4'is for preventing the injected fuel from reaching the cylinder bore through the top surface of the piston and diluting the engine oil. In this embodiment, homogeneous combustion is performed by injecting fuel in the intake stroke in all engine operating states without performing stratified charge combustion.

Also in this embodiment, the fuel injection valve 2 '
Is an air flow from the intake port 5 toward the exhaust port side of the cylinder bore to generate the tumble flow T1, that is,
Before descending along the exhaust port side of the cylinder bore, the two substantially fan-shaped sprays 10a, 10b obliquely downward from the air flow toward the piston top surface without interfering with the air flow advancing along the upper wall of the cylinder. Are jetted without interfering with each other. As a result, also in this embodiment, the two sprays having the tip-spreading shapes are sufficiently atomized during flight by the penetration force, and then sufficiently agitated by the tumble flow and the reverse tumble.

The detailed spray direction of the substantially fan-shaped spray 10 is such that the width direction of the substantially fan-shaped spray 10, that is, the direction of fan-shaped spray development is not parallel to the vertical plane parallel to the piston axis. Preferably, as shown in FIG. 7, the width direction of the substantially fan-shaped spray 10 is parallel to the horizontal plane perpendicular to the piston axis so that only the thickness of the substantially fan-shaped spray can be seen in the specific vertical section. Is being done. Due to such an injection direction, the substantially fan-shaped sprays are less likely to interfere with the airflows that vertically propagate along the cylinder bore without spreading in the cylinder much in the vertical direction, and are less likely to interfere with each other.

Of the two substantially fan-shaped sprays, the substantially fan-shaped spray 10a located on the piston top surface side has substantially the same injection direction as that of the first embodiment. However, by increasing at least one of the fan included angle and the thickness of the substantially fan-shaped spray, the penetration force is weakened as compared with that of the first embodiment. As a result, this substantially fan-shaped spray 10a is injected with its center plane in the thickness direction forming a relatively large angle with respect to the piston top surface, and therefore, it is likely to collide with the piston top surface during intake stroke injection. However, since the penetrating force is weakened, the time until it collides with the piston top surface can be extended, and good atomization can be realized during this time. Further, in the present embodiment, since the two fuel sprays are used, the fuel injection amount per unit time can be increased. As a result, it is possible to delay the fuel injection start timing in homogeneous combustion, which also makes it difficult for the substantially fan-shaped spray 10a to collide with the top surface of the piston, and makes full use of atomization by the penetration force. It becomes possible.

Of the two substantially fan-shaped sprays, the substantially fan-shaped spray 10b located on the upper side of the cylinder has at least one of a fan included angle and a thickness as compared with the substantially fan-shaped spray 10b located on the piston top surface side. It is made smaller and the penetration power is strengthened. In this substantially fan-shaped spray 10b, the center plane in the thickness direction is injected at a relatively small angle with respect to the piston top surface, so that the distance to the piston top surface (or cylinder bore) is the piston top surface side. Although it is longer than the substantially fan-shaped spray 10a located at, the long flight distance can be sufficiently flown by the strong penetration force.

In this way, in this embodiment, the two atomized sprays 10a and 10b are injected in the two directions in the cylinder, and even before the fuel sufficiently atomized by the penetration force is agitated by the air flow. It can be widely distributed in the cylinders and can be homogenized more favorably by stirring with an omega-shaped air flow.

Further, the substantially atomized fuel 10a which is injected at a relatively large angle with respect to the top surface of the piston makes it possible to make the fuel sufficiently atomized on the fuel injection valve side in the cylinder. On the other hand, the substantially fan-shaped spray 10b, which is injected at a relatively small angle with respect to the top surface of the piston, has a stronger penetrating force, and as a result, sufficiently atomized fuel is also provided on the opposite side of the fuel injection valve in the cylinder. Can exist. In this way, the sufficiently atomized fuel can be distributed in the entire cylinder even before being agitated by the air flow, and a well-homogenized homogeneous mixture can be formed.

Of course, also in this embodiment, the reverse tumble flow suppressing means similar to that described above is used to move the two substantially fan-shaped sprays 10a, 10b in the opening of the intake port 5 in the cylinder to the intake port side of the cylinder bore. An oncoming air flow is prevented from passing, and interference between the two substantially fan-shaped sprays 10a and 10b and the air flow generating the reverse tumble flow is prevented.

In this embodiment, the substantially fan-shaped spray 10a located on the piston top surface side is injected toward the swirl center of the reverse tumble flow T2 when the reverse tumble flow rises through the piston top surface, The substantially fan-shaped spray 10b located on the upper side of the cylinder is injected toward the vicinity of the swirl center of the tumble flow T1 when the tumble flow rises through the piston top surface. As a result, the two atomized fuels of the two substantially fan-shaped sprays are mixed in the tumble flow T
A one or reverse tumble stream T2 ensures reliable stirring, which is advantageous for the formation of a good homogeneous mixture.

[0045]

As described above, according to the in-cylinder injection type spark ignition internal combustion engine of the present invention, the pre-spreading spray injected from the fuel injection valve is sucked to generate a tumble flow during homogeneous combustion. The air is injected toward the top surface of the piston from this air flow without interfering with the air flow from the port toward the exhaust port of the cylinder bore. As a result, the divergent spray is sufficiently atomized during flight by the self-penetrating force without interfering with the air flow and being atomized. After being atomized in this way, the fuel is agitated by the tumble flow, and a good homogeneous mixture can be formed.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view in a cylinder in the latter half of a compression stroke showing a first embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.

2 is a piston top view of the in-cylinder injection spark ignition internal combustion engine of FIG. 1. FIG.

FIG. 3 is a schematic vertical sectional view in a cylinder in an intake stroke of the in-cylinder injection spark ignition internal combustion engine of FIG.

FIG. 4 is a schematic plan view of an upper portion of a cylinder.

5 is an enlarged sectional view taken along line QQ of FIG.

6 is an enlarged sectional view taken along line P-P of FIG.

FIG. 7 is a schematic vertical sectional view in a cylinder in an intake stroke showing a second embodiment of a direct injection spark ignition internal combustion engine according to the present invention.

FIG. 8 is a plan view of the piston of FIG.

[Explanation of symbols]

1 ... Spark plug 2, 2 '... Fuel injection valve 3, 3 '... piston 4 ... Cavity 5 ... Intake port 7 ... Exhaust port 10, 10a, 10b ... Mostly fan-shaped spray T1 ... Tumble style T2 ... Reverse tumble flow

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02F 1/42 F02F 1/42 K

Claims (9)

[Claims] 1. An in-cylinder injection spark ignition internal combustion engine in which an intake port and an exhaust port are connected to an upper part of a cylinder, and a fuel injection valve for injecting fuel into the cylinder is provided to perform at least homogeneous combustion, The tumble flow that descends along the exhaust port side of the cylinder bore and rises through the piston top surface is generated by the intake air introduced from the intake port into the cylinder, and the fuel injection valve is disposed on the intake port side above the cylinder. Is to inject fuel as a divergent spray, and the divergent spray interferes with the air flow from the intake port toward the exhaust port side of the cylinder bore to generate the tumble flow during the homogeneous combustion. The in-cylinder injection spark ignition internal combustion engine, characterized in that the fuel is injected from the airflow toward the top surface of the piston without performing the above. 2. The intake air introduced into the cylinder through the exhaust port side of the intake port in the cylinder opening generates the tumble flow, and is introduced into the cylinder through the anti-exhaust port side of the cylinder opening. The generated intake air creates a reverse tumble flow that descends along the intake port side of the cylinder bore and rises through the top surface of the piston, and the pre-spreading spray injected from the fuel injection valve is Passing between the piston top surface, the anti-exhaust port side of the in-cylinder opening, in the plan view facing the piston top surface, the passage range portion through which the divergent spray passes and the tip in the plan view. The reverse tumble flow is generated by the intake air that is divided into a non-passing range portion where the spread-shaped spray does not pass and is introduced into the cylinder through the non-passing range portion. The in-cylinder injection type according to claim 1, further comprising a reverse tumble flow suppressing unit that prevents the reverse tumble flow from being generated by intake air introduced into the cylinder through the overrange portion. Spark ignition internal combustion engine. 3. The fuel injection valve injects at least two sprays having a divergent shape that do not interfere with each other toward the piston top surface side from the air flow without interfering with the air flow. In-cylinder injection type spark ignition internal combustion engine according to. 4. The intake air introduced into the cylinder through the exhaust port side of the intake port in the cylinder opening generates the tumble flow, and is introduced into the cylinder through the anti-exhaust port side of the cylinder opening. The generated intake air descends along the intake port side of the cylinder bore to generate a reverse tumble flow that rises through the top surface of the piston, and the two sprays having the above-described flared shapes are injected into the cylinder. Passing between the inner opening and the piston top surface, the anti-exhaust port side of the cylinder inner opening, a passage range portion through which the two divergent sprays pass in plan view facing the piston top surface and the In the plan view, the two divergent sprays are divided into a non-passing range portion where the spray does not pass, and depending on the intake air introduced into the cylinder through the non-passing range portion, the reverse tumble flow is generated. 4. The reverse tumble flow suppressing means is provided to prevent the reverse tumble flow from being generated by the intake air introduced into the cylinder through the passage range portion. In-cylinder injection type spark ignition internal combustion engine according to. 5. One of the two flared sprays is located on the upper side of the cylinder, the other of the two flared sprays is located on the top side of the piston, and the one flared spray is The in-cylinder injection spark ignition internal combustion engine according to claim 4, which has a higher penetration force as compared with the other divergent spray. 6. The one-diverging spray having a smaller spreading angle and a higher penetration force than the other spray having a spreading shape.
In-cylinder injection type spark ignition internal combustion engine according to. 7. The one-divergent spray is sprayed toward the swirl center of the tumble flow, and the other swirl spray is sprayed near the swirl center of the reverse tumble flow. The cylinder injection type spark ignition internal combustion engine according to claim 5 or 6, characterized in that. 8. The intake port has a curved portion immediately upstream of the in-cylinder opening, and the reverse tumble flow suppressing means forms a part of a convex corner portion of the curved portion sharply to form the curved portion. The in-cylinder injection spark ignition according to claim 2 or 4, wherein the amount of intake air introduced into the cylinder through the passage range portion along the intake port wall surface downstream of the portion is reduced. Internal combustion engine. 9. The main inclination angle of the intake port with respect to the horizontal direction with respect to the piston axis so that the air flow advances along the exhaust port side of the cylinder upper wall where the in-cylinder opening of the exhaust port is provided. The in-cylinder injection spark ignition internal combustion engine according to any one of claims 1 to 8, wherein a relationship between the inclination angle of the upper wall of the cylinder and the exhaust port side with respect to the horizontal direction is selected.