JP3295975B2 - gasoline engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gasoline engine,
More specifically, the present invention relates to a direct injection gasoline engine that supplies gasoline directly into a combustion chamber.

[0002]

2. Description of the Related Art As an in-cylinder injection gasoline engine for directly supplying gasoline into a combustion chamber, for example, the one shown in FIG. 12 is known. A fuel injection valve 51 disposed facing the combustion chamber 50 is disposed so as to face the exhaust valve 52 (see JP-A-63-230920).

[0003]

However, in such a direct injection gasoline engine, the fuel injected from the fuel injection valve 51 is made to collide directly with the exhaust valve 52 to be atomized. Meanwhile, the fuel injected from the fuel injection valve 51 passes through the vicinity of the spark plug 54, and the fuel is unlikely to be present near the spark plug 54 at the ignition timing.
As a result, the ignitability deteriorates, causing combustion fluctuations,
There is a problem that a stable combustion state cannot be obtained.

[0004] The present invention has been made in view of such problems, and an object of the present invention is to provide a direct injection gasoline engine capable of obtaining a stable combustion state.

[0005]

In order to solve the above problems, the present invention provides a combustion chamber formed in a cylinder head and located at an upper end of a cylinder, an intake port opening to the combustion chamber, In a gasoline engine having a spark plug disposed to face a combustion chamber, a tumble forming means for forming a tumble in the cylinder is provided for intake air introduced into the cylinder from an intake port, and a first tumble direction pointing to the spark plug is provided. A multi-injection fuel injection valve having an injection port and a second injection port directed in a direction along the flow of the tumble flow is provided on the cylinder head facing the combustion chamber.

[0006]

In order to obtain stable combustion, it is effective to form a tumble (vertical vortex) in the cylinder and perform stratified combustion in which the air-fuel ratio near the spark plug is locally increased. According to the above, the fuel injected from the first injection port forms a dense mixture layer near the spark plug, which has a relatively small flow, and the fuel injected from the second injection port rides on a tumble to remove most of the air in the cylinder. Since a lean mixture layer is formed, stratification of the rich mixture layer and the thin mixture layer is obtained, thereby enabling stratified combustion. As a result, good ignitability can be obtained, and at the same time, a homogeneous air-fuel mixture can be formed in the vicinity of the ignition plug, a stable combustion state can be obtained, and the lean burn limit is expanded.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a longitudinal sectional view of a direct injection gasoline engine according to the present embodiment, FIG. 2 is a view along arrow AA in FIG. 1, and FIG. 3 is a view along arrow BB in FIG.

Referring to FIGS. 1 to 3, reference numeral 1 denotes a cylinder block having a cylinder 3, and 2 denotes a cylinder head defining a combustion chamber 4. The cylinder head 2 is formed with two intake ports 5 per cylinder and two exhaust ports 6 per cylinder, each opening to the combustion chamber 4.

Each intake port 5 is provided with an intake valve 7 for opening and closing the intake port 5, and a valve guide boss 8 for supporting the intake valve 7 is formed above each intake port 5. A valve guide 9 is interposed between the guide boss 8 and the guide boss 8. A valve seat 13 on which an umbrella portion 7a of the intake valve 7 is seated is fixed to an opening of the intake port 5. The same applies to each exhaust port 6.
An exhaust valve 10 for opening and closing the exhaust valve 10 is provided, and a valve guide boss 11 for supporting the exhaust valve 10 is formed above each exhaust port 6. A valve is provided between the exhaust valve 10 and the valve guide boss 11. A guide 12 is interposed, and a valve seat 14 on which an umbrella portion 10a of the exhaust valve 10 is seated is fixed to an opening of the exhaust port 6.

The shape of the intake port 5 is determined from
The intake air guided into the inside is configured to form a tumble 15 (strong longitudinal vortex) as shown in FIG. 4 in the cylinder 3, thereby forming a tumble forming means 5 '. That is, the intake air from the intake port 5 is supplied to the umbrella portion 7a of the intake valve 7 in the open state.
5 flows into the cylinder 3 through a circumferential space formed between the valve seat 13 and the valve seat 13. When considering the flow of intake air in this circumferential space, as shown in FIG. In short, the flow of intake air from the portion 17 near the wall of the cylinder 3 into the combustion chamber 4 is suppressed so that more intake air flows from the portion near the center of the combustion chamber 4 than the portion 17 near the wall of the cylinder 3. For this purpose, the shape of the intake port 5 is determined. The cross-sectional shape of the intake port 5 is as shown in the CC section.

In addition, as tumble forming means,
Although illustration is omitted, it is conceivable to provide an intake control valve or an assist air supply device in the intake port 5 for giving an appropriate directionality to the intake air flowing through the intake port 5.

Referring to FIGS. 1 to 3, an ignition plug 19 is provided in the cylinder head 2 so as to face the vicinity of the center of the combustion chamber 4. The cylinder head 2 has a multi-injection fuel injection valve 2 directly facing the combustion chamber 4 from between the intake ports 5 and 5.
0 is located in the cylinder horizontal direction, facing the center of the combustion chamber 4.

The multi-injection fuel injection valve 20 has three injection ports, one of which is a first injection port 21 pointing to the spark plug 19.
And the other two are second orifices 2 oriented in a direction along the flow of the tumble 15, 15 formed in the cylinder 3.
2,22. These first nozzle 21 and second nozzle 2
The flow of the fuel injected from the fuel injection nozzles 2 and 22 is as shown in FIGS. 1 to 3, that is, the first injection port 21 forms the spray a toward the vicinity immediately below the ignition plug 19, and the second injection ports 22 and 22 Sprays b, b aiming at the vicinity immediately below the exhaust valve 10 immediately below the intake valve 7 and slightly downwardly with respect to the horizontal direction of the cylinder. Then, the sprays b formed from the second injection port 22 pass on both sides of the ignition plug 19 and flow down the cylinder 3 on the tumbles 15.

FIG. 6 is a sectional view showing the vicinity of the injection port of the fuel injection valve 20. The fuel injection valve 20 includes a valve body 23 forming an outer shell.
A fuel supply hole 24 drilled at the tip of the valve body 23;
A needle valve 25 movably housed in the valve body 23 to open and close the fuel supply hole 24, and a cap 26 attached to the tip of the valve body 23. FIG. 7 is a partially enlarged sectional view of FIG.
Between the valve body 23 and the cap 26, the first orifice 21 and the second orifices 22, 22 pointing in the predetermined directions as described above.
Is opened.

In such a fuel injection valve 20, when fuel is supplied from a fuel pump (not shown) into the valve body 23, the needle valve 25 is lifted rightward in the figure. At this time, the fuel is ejected from the fuel injection holes 24, and then passes through the first injection ports 21 and the second injection ports 22, 22 formed in the plate 27, and sprays a and sprays b, b are injected in desired directions. To form

As shown in FIG. 8, the diameter of the first injection port 21 for injecting the fuel toward the vicinity of the ignition plug 19 is the diameter of the second injection port 22 for injecting the fuel immediately below the exhaust valve 10. Is smaller than. This is to make the distance of the injected fuel from the first nozzle 21 shorter than the distance of the injected fuel from the second nozzles 22, 22. Since the diameter is smaller than that of the second injection ports 22, 22 aimed at immediately below the exhaust valve 10, atomization of the fuel injected from the second injection ports 22 is promoted, and the reach of the injected fuel is shortened. More specifically, when the diameter of the injection hole is large as in the second injection ports 22, 22, the particle diameter of the fuel injected from the injection hole is generally large, and when the diameter of the injection hole is small as in the first injection port 21. From this, the particle diameter of the fuel tends to be smaller than that from the second nozzles 22 and atomized. On the other hand, the first nozzle 21 and the second nozzle 2
Since the fuel supply sources to the fuel tanks 2 and 22 are the same, the flow rates of the fuel ejected from both the injection ports are substantially the same.
Since the kinetic energy of the fuel particles ejected from the nozzle depends on the mass, the larger the particle diameter of the fuel, the larger the kinetic energy proportional to the cube of the particle diameter is obtained. become longer.

Thus, the sprays b formed from the second injection ports 22 and 22 reach the vicinity immediately below the exhaust valve 10 immediately below the intake valve 7, and the spray a generated by injection from the first injection port 21 is Therefore, the fuel gas can be present in the vicinity of the ignition plug 19 without passing through the vicinity of the ignition plug 19, and a dense mixture layer is formed in the vicinity of the ignition plug 19.

By forming the diameters of the second injection ports 22 and 22 to be the same as those of the first injection ports 21, the spray formed from the second injection ports 22 and 22 does not reach the vicinity immediately below the exhaust valve 10. , A tumble formed in the cylinder 3.

FIG. 9 is a diagram showing the fuel injection timing. The course of the fuel injected from the second injection ports 22, 22 is as follows.
It is taken into consideration that the intake valve 7 is not obstructed by the open intake valve 7, that is, the fuel supply is performed from the latter half of the intake stroke when the intake valve 7 is closed to the compression stroke. Reference numeral 28 denotes a piston housed in the cylinder 1.

Next, the operation based on such a configuration will be described.

As shown in FIG. 10, the intake air guided from the intake port 5 into the combustion chamber 4 corresponds to each intake port 5,
Two independent strong tumbles 15, 15 are formed. The two tumbles 15, 15 formed in the cylinder 3 are:
Since it is a vertical vortex in the cylinder axis direction, the piston 28 is crushed as it rises in the compression stroke, and when the piston 28 reaches the vicinity of the compression top dead center, as shown in FIG.
5, 15 are disintegrated and converted into small-scale vortices 29. This small-scale vortex 29 greatly contributes to an increase in combustion speed and stabilization of combustion, and thus has a function of shortening a combustion period and expanding a lean burn limit.

On the other hand, the two tumbles 15 and 15 do not mix with each other until they collapse into a small-scale vortex 29 near the compression top dead center, and exist independently of each other. , A vortex 30 that does not mix independently of the tumbles 15, 15 occurs near the spark plug 19. The vortex 30 exists independently of the vortex 29 even after the tumble 15 has collapsed.

The fuel injected from the second injection ports 22, 22 is supplied to the tumbles 15, 15 in a substantially tangential direction. To form an appropriate mixture layer. And
The fuel injected from the first injection port 21 passes between the two tumbles 15 having relatively low flow and reaches the vicinity of the spark plug 19, and the fuel that has reached the vicinity of the spark plug 19 is located near the spark plug 19. Stayed here without passing through,
A vortex 30 formed locally in the vicinity of the ignition plug 19 forms a dense mixture layer.

That is, just before the ignition, the vortex 29 and the vortex 3
Since 0 is independently present, the separation of the air-fuel mixture can be stably stored in a strong flow field, and a dense air-fuel mixture layer can be maintained near the ignition plug 19.

Accordingly, although it is an in-cylinder injection gasoline engine which is generally said to have relatively poor fuel atomization, the fuel supplied on the strong tumblers 15 mixes with most of the air in the cylinder 3. Accordingly, stratification of a lean mixture layer formed by the above and a rich mixture layer formed by the fuel supplied near the spark plug 19 and the local air near the spark plug 19 is realized, whereby stratified combustion is performed. As a result, the lean burn limit is expanded, and a stable combustion state can be obtained even when the lean burn is performed.

In this embodiment, a gasoline engine having two intake valves and two exhaust valves per cylinder has been described. However, the present invention is not limited to this.
The present invention is also applicable to a gasoline engine having two or one intake valve and one exhaust valve.

[0028]

As described above, according to the present invention, a dense mixture layer formed near the spark plug and a thin mixture layer formed on a tumble can be stratified. Combustion is realized. Thereby, good ignitability can be obtained, and at the same time, a stable combustion state can be obtained, and the lean burn limit is expanded.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a direct injection gasoline engine according to one embodiment.

FIG. 2 is a view taken in the direction of arrows AA in FIG. 1;

FIG. 3 is a view taken in the direction of arrows BB in FIG.

FIG. 4 is a view for explaining a tumble formed in a cylinder;

FIG. 5 illustrates a tumble forming unit.

FIG. 6 is a sectional view showing the vicinity of the injection port of the fuel injection valve.

FIG. 7 is a partially enlarged sectional view of FIG. 6;

8 is a partially enlarged sectional view of FIG. 6;

FIG. 9 is a diagram showing fuel injection timing.

FIG. 10 is a diagram illustrating a tumble and a vortex formed in a cylinder.

FIG. 11 is a view for explaining collapse of a tumble;

FIG. 12 shows a conventional direct injection gasoline engine.

[Explanation of symbols]

 2 Cylinder head 3 Cylinder 4 Combustion chamber 5 Intake port 5 'Tumble forming means 15 Tumble 19 Spark plug 20 Fuel injection valve 21 First injection port 22 Second injection port

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-10674 (JP, A) JP-A-1-273873 (JP, A) JP-A-1-267328 (JP, A) JP-A-5-107 280343 (JP, A) JP-A-62-255529 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 1/00-23/10

Claims (1)

(57) [Claims] 1. A gasoline engine having a combustion chamber formed in a cylinder head and located at an upper end of a cylinder, an intake port open to the combustion chamber, and a spark plug arranged to the combustion chamber. A tumble forming means for forming a tumble in the cylinder from the intake port into the intake air introduced into the cylinder, wherein the first orifice pointing to the spark plug and the second orifice pointing to the direction along the flow of the tumble are provided. A gasoline engine having a multi-injection fuel injection valve disposed in a cylinder head facing a combustion chamber.