JPH09280055A - Direct cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure which is suitable for a direct cylinder injection type spank ignition engine. SOLUTION: An ignition plug 4 faces a combustion chamber 3 from a position where it is closer to an air suction port 21 than an injector 6 between the air suction 21 and an air exhaust port on a ceiling wall 2 of the combustion chamber, and the air suction port 21 is inclined for the central line of a cylinder so that suction air which flows in an air cylinder from the air suction port 21 descends along an inclined face 24 on the air exhaust port side on the ceiling wall 20 of the combustion chamber. A cavity 11 which is recessed is formed on a top face 10 of a piston 1, and a guide part 12 which is inclined toward the ignition plug 4 is formed in the cavity 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an intake system in a direct cylinder injection type spark ignition engine.

[0002]

2. Description of the Related Art In order to stratify an air-fuel mixture that collects fuel near an ignition plug, an injector (fuel injection valve) faces the cylinder and direct fuel is injected into the cylinder. There is an injection spark ignition engine.

As a conventional direct cylinder injection type spark ignition engine, there is one in which an intake port is made to stand upright along a cylinder wall as disclosed in, for example, Japanese Patent Laid-Open No. 6-207542.

The intake air that has flowed into the cylinder from the upright intake port descends along the cylinder wall and then causes a reverse tumble that swirls along the top surface of the piston.

The fuel injected from the injector into the cylinder is atomized and vaporized in the course of swirling due to the reverse tumble, and liquid fuel is prevented from adhering to the ignition plug, and misfire is prevented and stabilized. Flammability is obtained.

[0006]

However, in such a conventional direct cylinder injection type spark ignition engine, the intake manifold has a structure in which the upright intake port is provided so as to penetrate through the upper portion of the cylinder head. Must be connected to the upper part of the cylinder head, which may cause a problem of increasing the total height of the engine.

Further, since the intake port is provided upright on the cylinder head, there is a problem that the degree of freedom of arrangement of the water jacket formed around the combustion chamber wall of the cylinder head is reduced.

The present invention has been made in view of the above problems, and an object thereof is to provide a combustion chamber structure suitable for a direct cylinder injection type spark ignition engine.

[0009]

According to a first aspect of the present invention, there is provided a direct cylinder injection type spark ignition engine having an intake port for introducing intake air into a cylinder, an injector for injecting fuel into the cylinder, and a mixture in the cylinder. In a direct in-cylinder injection type spark ignition engine equipped with a spark plug for igniting the air and an exhaust port for discharging exhaust gas from the cylinder, an intake port is provided on a combustion chamber ceiling wall defining a combustion chamber with a piston. It is composed of an intake port side inclined surface that opens and an exhaust port side inclined surface that opens the exhaust port.The injector faces the combustion chamber from between the intake port and the exhaust port of the combustion chamber ceiling wall, and the spark plug is attached to the combustion chamber ceiling wall. Between the intake port and the exhaust port of the engine, the injector is made to face the combustion chamber from a position closer to the intake port, and the intake air flowing into the cylinder from the intake port descends along the inclined surface on the exhaust port side. The sea urchin intake port is inclined with respect to the cylinder center line to form a cavity recessed in a concave shape on the top surface of the piston, forming the guide portion inclined toward the spark plug in the cavity.

According to a second aspect of the present invention, in the direct cylinder injection type spark ignition engine of the first aspect, the cavity is opened toward a cylinder wall which is connected to the exhaust port side inclined surface.

A direct cylinder injection type spark ignition engine according to a third aspect is the invention according to the first or second aspect,
The ridgeline of the guide portion with respect to the top surface of the piston is formed by being curved so as to surround the fuel injection range of the injector.

According to a fourth aspect of the present invention, there is provided a direct cylinder injection type spark ignition engine according to the first aspect, wherein the top surface of the piston is inclined along the combustion chamber ceiling wall. .

[0013]

In the direct cylinder injection type spark ignition engine according to the first aspect, air is sucked into the cylinder from the intake port as the intake valve is opened. During the intake stroke in which the piston descends or the compression stroke in which the piston rises, the injector opens and fuel is injected into the combustion chamber. In a state where the air sucked into the cylinder through the intake port is compressed by the piston, the fuel is ignited and burned through the spark plug. The burned gas is discharged from each exhaust port as the exhaust valve is opened during the exhaust stroke in which the piston moves up after the piston is lowered and the rotational force is taken out through the crankshaft. Each of these steps is continuously repeated.

The intake flow flowing into the cylinder through the intake port descends along the inclined surface of the exhaust port and the cylinder wall, and then advances to the top surface of the piston to generate a tumble.

On the other hand, the fuel injected from the injector into the cylinder swirls together with the tumble, but since the injector is located downstream of the spark plug with respect to the tumble, the liquid fuel directly flows to the spark plug. It is possible to avoid adhesion and prevent misfire.

The fuel injected from the injector is heated by the piston in the process of swirling along the cavity of the piston by the tumble, and atomization and vaporization thereof proceed.

Since the guide portion of the cavity is inclined toward the spark plug, the fuel spray swirling with the tumble on the cavity rises toward the spark plug along the guide portion. As a result, the rich air-fuel mixture is collected in the vicinity of the spark plug, and the air-fuel mixture is stratified.

By thus concentrating the fuel in the vicinity of the spark plug, ignition is reliably performed. As a result, the limit value of the lean air-fuel ratio at which combustibility is ensured is expanded, and fuel consumption is reduced. Further, it is not necessary to increase the fuel injection amount in the cold state, and the emission can be improved.

Since the intake port is largely inclined with respect to the cylinder center line so as to cause tumble, and the upstream end of the intake port is opened to the side wall portion of the cylinder head, the intake manifold is connected to the side wall portion of the cylinder head. You can As a result, the height of the engine is reduced and the degree of freedom of arrangement of the water jacket formed around the combustion chamber wall of the cylinder head is reduced as compared with the conventional device having an upright intake port that penetrates the upper portion of the cylinder head. Can be increased.

In the direct cylinder injection type spark ignition engine according to the second aspect, since the cavity is formed so as to open toward the cylinder wall connected to the inclined surface on the exhaust port side, the intake air introduced from the intake port is After descending along the exhaust port side inclined surface and the cylinder wall, it smoothly advances to the cavity, and a strong tumble can be generated in the central portion of the combustion chamber.

By generating a strong tumble in the cylinder in this way, stratification of the air-fuel mixture that collects the fuel injected from the injector into the cylinder in the vicinity of the spark plug is achieved, and the flame is propagated by the gas flow of the tumble. Be prompted. As a result, the limit value of the lean air-fuel ratio at which combustibility is ensured is expanded, and fuel consumption is reduced.

In the direct cylinder injection type spark ignition engine according to claim 3, since the ridge of the guide portion with respect to the piston top surface is curved so as to surround the fuel injection range of the injector, the rich mixing is performed through the guide portion. The air is effectively collected in the center of the combustion chamber.

In the direct injection type spark ignition engine according to the fourth aspect, since the top surface of the piston is inclined along the combustion chamber ceiling wall, when the piston reaches the top dead center, the piston and the combustion chamber ceiling are arranged. A high compression ratio is achieved by concentrating the volume of the combustion chamber defined between the walls in the cavity.

[0024]

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

As shown in FIGS. 1 and 3, the combustion chamber 3 is defined between the combustion chamber ceiling wall 20 formed in the cylinder head 2 and the piston 1.

Combustion chamber ceiling wall 2 inclined to a pent roof type
At 0, two intake ports 21 and two exhaust ports 22 face each other and open. That is, the combustion chamber ceiling wall 20 is configured by the intake port side inclined surface 23 where each intake port 21 opens and the exhaust port side inclined surface 24 where each exhaust port 22 opens.

An injector 6 and a spark plug 4 are provided which face the combustion chamber 3 from the central portion of the combustion chamber ceiling wall 20. Two intake valves 7 that sandwich the injector 6 and the spark plug 4
And two exhaust valves (not shown) are provided facing each other.

The injector 6 faces the combustion chamber 3 laterally of the two exhaust valves and in the middle of the two exhaust valves. The injector 6 is arranged substantially parallel to the cylinder center line.

The spark plug 4 is located on the side of the two intake valves 7,
Moreover, it is located in the middle of both intake valves 7 and faces the combustion chamber 3. That is, the spark plug 4 faces the combustion chamber 3 from a position closer to each intake port 21 by the injector 6 between each intake port 21 and each exhaust port 22 of the combustion chamber ceiling wall 20.

The intake air flowing from each intake port 21 into the combustion chamber 3 is shown by an arrow in FIG.
And tumble generating means for descending along the cylinder wall 5 to generate tumble. As a means for generating tumble, each intake port 21 has a passage center as shown in FIG.
In the front view, the linear extension extends and is largely inclined with respect to the cylinder center line so as to face the exhaust port side inclined surfaces 24 and the cylinder wall 5.

The top surface 10 of the piston 1 is provided with a cavity 11 which is recessed in a concave shape. The cavity 11 is disposed below the exhaust port side inclined surface 24 from the center of the piston top surface 10.

The injector 6 has a nozzle 1 having a cavity 1
1, the fuel spray injected from the injection port radially spreads toward the cavity 11.

A guide portion 12 that is inclined toward the spark plug 4 is formed in the cavity 11. The fuel spray injected from the injector 6 swirls together with the tumble generated in the combustion chamber 3 and rises along the guide portion 12, so that the rich air-fuel mixture is collected in the vicinity of the spark plug 4.

The ridge line 13 of the guide portion 12 with respect to the piston top surface 10 is formed to be curved so as to surround the fuel injection range of the injector 6.

The cavity 11 has an inclined surface 24 on the exhaust port side.
And is formed to be open toward the cylinder wall 5. That is, the ridgeline 13 of the cavity 11 with respect to the piston top surface 10 is curved in a dogleg shape, and both ends 14 thereof reach the outer circumference of the piston 1.

With the above construction, the operation will be described.

As each intake valve 7 is opened, air is taken into each cylinder from each intake port 21. During the intake stroke in which the piston 1 descends or the compression stroke in which the piston 1 rises, the injector 6 opens and fuel is injected into the combustion chamber 3. In addition, FIG. 1 shows 60 ° before the compression top dead center.
FIG. 6 is a cross-sectional view at (60 ° BTDC), and in the present embodiment, at this timing, the fuel spray is radially injected from the injector 6 toward the cavity 11 as illustrated.

In a state where the air sucked into the cylinder through each intake port 21 is compressed by the piston, the fuel is ignited and burned through the spark plug 4. Burned gas is piston 1
Is taken out and the rotational force is taken out via the crankshaft, and then the piston 1 is discharged from each exhaust port 22 as the exhaust valve is opened during the exhaust stroke. Each of these steps is continuously repeated.

The intake flow flowing into the cylinder through each intake port 21 descends along the exhaust port side inclined surface 24 and the cylinder wall 5 and then on the piston top surface as shown by the outline arrow in FIG. Proceed to the top 10 to produce a tumble that turns.

On the other hand, the fuel injected from the injector 6 into the cylinder is once lowered by this tumble.
Avoid the liquid fuel from directly adhering to the spark plug 4,
It can prevent a misfire.

The fuel injected from the injector 6 is heated by the piston 1 in the process of swirling along the cavity 11 of the piston 1 by the tumble, and the atomization and vaporization thereof proceed.

The guide portion 12 of the cavity 11 is the spark plug 4
The fuel spray swirling along with the tumble on the cavity 11 rises to the central portion of the combustion chamber 3 along the guide portion 12 because the fuel spray is inclined toward. As a result, FIG.
As shown in, the rich mixture is collected in the vicinity of the spark plug 4,
The mixture is stratified.

By thus concentrating the fuel in the vicinity of the spark plug 4, ignition is reliably performed. As a result, the limit value of the lean air-fuel ratio at which combustibility is ensured is expanded, and fuel consumption is reduced. Further, it is not necessary to increase the fuel injection amount in the cold state, and the emission can be improved.

The cavity 11 has an inclined surface 24 on the exhaust port side.
Further, since it is formed so as to open toward the cylinder wall 5, the intake air guided from each intake port 21 descends along the exhaust port side inclined surface 24 and the cylinder wall 5 and then smoothly advances to the cavity 11 for combustion. A strong tumble can be generated in the center of the chamber 3.

By generating a strong tumble in the cylinder in this way, the fuel-air injected from the injector 6 into the cylinder is stratified in the vicinity of the spark plug 4, and the gas flow of the tumble causes the flame to be stratified. Propagation is encouraged. As a result, the limit value of the lean air-fuel ratio at which combustibility is ensured is expanded, and fuel consumption is reduced.

As another embodiment, as shown in FIGS. 6 and 7, the cavity 11 may be formed in a groove shape parallel to the crankshaft.

As yet another embodiment, as shown in FIGS. 8 and 9, it is conceivable to form the cavity 11 in a spherical shape.

However, in either case, the cavity 11
Does not open toward the cylinder wall that is connected to the exhaust port side inclined surface, the intake air guided from the intake port decreases along the exhaust port side inclined surface and the cylinder wall and then weakens the force that advances to the cavity 11, Can't generate a strong tumble.

In the first embodiment, the piston top surface 1
Since the ridgeline 13 of the guide portion 12 with respect to 0 is curved so as to surround the fuel injection range of the injector 6, as shown in FIG. 4, the rich air-fuel mixture is guided to the central portion of the combustion chamber 3 via the guide portion 12. Collected effectively.

As another embodiment, FIG. 10 and FIG.
1, the guide portion 1 for the piston top surface 10
It is also conceivable that the ridgeline 2 of 2 is formed in a straight line parallel to the crankshaft and the cavity 11 is opened toward the cylinder wall connected to the exhaust port side inclined surface.

However, in this case, although the power of the tumble can be increased, the fuel swirling together with the tumble diffuses largely in the cylinder center line direction (engine front-rear direction), and the rich mixture is effectively collected in the central portion of the combustion chamber. I can't.

As still another embodiment, FIG. 12 and FIG.
As shown in FIG. 3, the piston top surface 10 may be inclined and formed in a pent roof type.

The piston top surface 10 is an intake port side inclined surface 2 of the combustion chamber ceiling wall 10 which is also inclined in a pent roof type.
3 and a sloped surface 16 that slopes facing the exhaust port side sloped surface 24.

In this case, when the piston 1 reaches the top dead center, the volume of the combustion chamber 3 defined between the piston 1 and the combustion chamber ceiling wall 10 is concentrated in the cavity 11 to obtain a high compression ratio. To be

As still another embodiment, FIG. 14 and FIG.
As shown in FIG. 5, the ridgeline 13 of the cavity 11 with respect to the piston top surface 10 may be curved and formed in a U shape. Both ends 14 of the ridgeline 13 are substantially orthogonal to the crankshaft and reach the outer circumference of the piston 1.

In this case, since the cavity 11 is formed so as to open toward the cylinder wall connected to the exhaust port side inclined surface, the intake air introduced from each intake port is directed to the exhaust port side inclined surface 24 and the cylinder wall 5. After descending along, it smoothly advances to the cavity 11, and a strong tumble can be generated in the central portion of the combustion chamber 3.

In any of the embodiments, each intake port 21 is largely inclined with respect to the cylinder center line and its upstream end is open to the side wall of the cylinder head 2. Therefore, the intake manifold is connected to the side wall of the cylinder head 2. Can be connected to the department. As a result, the height of the engine is reduced and a water jacket or the like formed around the combustion chamber ceiling wall 10 of the cylinder head 2 is provided as compared with the conventional device having an upright intake port that penetrates the upper portion of the cylinder head. The degree of freedom in arranging can be increased.

[0058]

As described above, according to the direct cylinder injection type spark ignition engine of the first aspect, the fuel spray swirling together with the tumble on the cavity rises toward the spark plug along the guide portion. Therefore, stratification of the air-fuel mixture is achieved, the limit value of the lean air-fuel ratio at which combustibility is ensured is expanded, and fuel consumption is reduced.

Since the intake port is largely inclined with respect to the cylinder center line so as to cause tumble, and the upstream end of the intake port is opened to the side wall portion of the cylinder head,
The height of the engine is reduced and the degree of freedom of arrangement of the water jacket formed around the wall of the combustion chamber of the cylinder head is increased, as compared with a conventional device having an upright intake port that penetrates the upper portion of the cylinder head. be able to.

According to the direct cylinder injection type spark ignition engine of the second aspect, since the cavity is formed so as to open toward the cylinder wall connected to the inclined surface on the exhaust port side, it is guided from the intake port. After the intake air descends along the inclined surface of the exhaust port side and the cylinder wall, it progresses smoothly to the cavity, creating a strong tumble in the center of the combustion chamber,
The fuel consumption can be reduced by expanding the limit value of the lean air-fuel ratio that ensures combustibility.

According to the direct cylinder injection type spark ignition engine of the third aspect, since the ridgeline of the guide portion with respect to the piston top surface is curved so as to surround the fuel injection range of the injector, the guide portion is used. The rich air-fuel mixture is effectively collected in the central part of the combustion chamber, and the limit value of the lean air-fuel ratio for ensuring the combustibility is expanded to reduce fuel consumption.

According to the direct cylinder injection type spark ignition engine of the fourth aspect, since the top surface of the piston is inclined along the ceiling wall of the combustion chamber, when the piston reaches the top dead center, the combustion with the piston occurs. The volume of the combustion chamber defined between the chamber ceiling walls is concentrated in the cavity to achieve a high compression ratio of the engine.

[Brief description of drawings]

FIG. 1 is a schematic front view of an engine in an intake stroke showing an embodiment of the present invention.

FIG. 2 is a schematic front view of the engine at the same ignition timing.

FIG. 3 is a schematic plan view of the combustion chamber ceiling wall.

FIG. 4 is a schematic plan view of the piston.

FIG. 5 is a schematic front view of the piston.

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

FIG. 7 is a schematic front view of the piston.

FIG. 8 is a schematic plan view of a piston showing still another embodiment.

FIG. 9 is a schematic front view of the piston.

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

FIG. 11 is a schematic front view of the same piston.

FIG. 12 is a schematic plan view of a piston showing still another embodiment.

FIG. 13 is a schematic front view of the piston.

FIG. 14 is a schematic plan view of a piston showing still another embodiment.

FIG. 15 is a schematic front view of the piston.

[Explanation of symbols]

 1 Piston 2 Cylinder Head 3 Combustion Chamber 4 Spark Plug 5 Cylinder Wall 6 Injector 10 Piston Top Surface 11 Cavity 12 Guide Part 13 Ridge Line 15 Piston Inclined Surface 16 Piston Inclined Surface 20 Combustion Chamber Ceiling Wall 21 Intake Port 22 Exhaust Port 23 Intake Port Inclined Surface 24 Exhaust port inclined surface

Claims (4)

[Claims] 1. An intake port for introducing intake air into a cylinder, an injector for injecting fuel into the cylinder, an ignition plug for igniting an air-fuel mixture in the cylinder, and an exhaust port for exhausting exhaust gas from the cylinder. In the direct cylinder injection type spark ignition engine equipped with, the combustion chamber ceiling wall that defines the combustion chamber with the piston is composed of the intake port side inclined surface where the intake port opens and the exhaust port side inclined surface where the exhaust port opens. The injector is exposed to the combustion chamber from between the intake port and the exhaust port of the combustion chamber ceiling wall, and the spark plug is located between the intake port and the exhaust port of the combustion chamber ceiling wall from the position closer to the intake port than the injector. The intake port to the cylinder center line so that the intake air flowing into the cylinder from the intake port descends along the inclined surface on the exhaust port side. Forming a cavity recessed in a concave shape on a surface, directly in-cylinder injection spark ignition engine, characterized in that the formation of the guide portion inclined toward the spark plug in the cavity. 2. The direct in-cylinder injection spark ignition engine according to claim 1, wherein the cavity is formed so as to be opened toward a cylinder wall which is connected to the inclined surface on the exhaust port side. 3. A direct cylinder injection type spark ignition according to claim 1, wherein a ridgeline of the guide portion with respect to the top surface of the piston is formed so as to be curved so as to surround a fuel injection range of the injector. engine. 4. The piston according to claim 1, wherein a top surface of the piston is formed to be inclined along a ceiling wall of the combustion chamber.
A direct cylinder injection type spark ignition engine according to any one of 1.