JP2002195041A - Structure of cylinder fuel injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the volatility of fuel simultaneously with obtaining a prescribed compression ratio in a cylinder fuel injection type internal combustion engine formed with a cavity 12 recessed in the top face of a piston 11, installing an ignition plug 9 in a cylinder head 1, and installing a fuel injection valve 10, in a state in which the fuel from its jet hole 10a' in its tip part is jetted toward the cavity. SOLUTION: While the jet hole 10a' in the fuel injection valve is constituted into a slit jet hole with a rectangular cross section, the cavity 12 is formed into a narrow rectangular shape with its longitudinal direction of the slit jet hole, as viewed from the axial direction of the cylinder, is set longer and the orthogonal direction thereto set shorter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an in-cylinder fuel injection type internal combustion engine in which fuel is directly injected and supplied into a cylinder.

[0002]

2. Description of the Related Art In an in-cylinder fuel injection type internal combustion engine, as described in, for example, Japanese Patent Application Laid-Open No. H11-343947, fuel is supplied during an intake stroke. One that forms a uniform mixture and burns with an ignition plug (homogeneous combustion method)
As described in Japanese Patent Application Laid-Open No. 2000-248944, a method in which fuel is injected and supplied at the end of the compression stroke to form a mixture in the vicinity of an ignition plug in a stratified form and combust (stratified combustion method) And, for example,
As described in JP-A-11-82028,
There is a combination of the homogeneous combustion system and the stratified combustion system.

Conventionally, in either case, a cavity is formed in the top surface of the piston and fuel is injected into the cavity, so that the injected fuel can adhere to the inner surface of the cylinder. It is configured to promote the vaporization of the fuel as little as possible.

[0004]

However, in order to more effectively achieve the effect of providing the cavity, that is, the effect of minimizing the adherence of the injected fuel to the inner surface of the cylinder, the cavity must be provided. Should occupy as much as possible the area occupying the top surface of the piston.

That is, by increasing the ratio of the area occupied by the cavity to the top surface of the piston, the adhesion of the fuel injected from the fuel injection valve to the inner surface of the cylinder can be reduced. When the point is reached, the internal volume of the combustion chamber increases by an amount corresponding to the increase in the area ratio of the cavity, so that a predetermined compression ratio cannot be obtained.

In other words, in the conventional configuration, in order to reduce the amount of fuel adhering to the inner surface of the cylinder and to promote its vaporization, if the area ratio of the cavity to the top surface of the piston is increased, a predetermined compression When the ratio of the area occupied by the cavity to the top surface of the piston is reduced to obtain a predetermined compression ratio, the injected fuel flows out of the cavity to the inner surface of the cylinder. However, there is a problem that the amount of fuel vaporized increases and the vaporization of the fuel decreases.

An object of the present invention is to solve this problem.

[0008]

In order to attain this technical object, the present invention provides a method of forming a hollow in a top surface of a piston in a cylinder, while installing a spark plug in a cylinder head at the top of the cylinder. A fuel injection valve is mounted so as to be seen in the region of the cavity when viewed from the axial direction of the cylinder, and a fuel injection valve is mounted so as to inject fuel into the cavity from an injection hole at a tip end thereof. In the fuel injection type internal combustion engine, the injection hole at the tip end of the fuel injection valve is formed as a slit-shaped injection hole having a rectangular cross section, while the cavity is viewed from the axial direction of the cylinder, and the length of the slit-shaped injection hole is elongated. It is characterized in that it has an elongated shape in which the direction is lengthened and the direction perpendicular to the direction is shortened. "

[0009]

In this configuration, fuel is injected from the slit-shaped injection hole of the fuel injection valve while spreading in a fan shape in a flat state having a relatively small thickness, so that the injected fuel is injected. The contact area with air can be improved as compared with the case where fuel is injected in a conical shape.

On the other hand, when the cavity at the top surface of the piston is viewed from the axial direction of the cylinder, the longitudinal direction of the slit-shaped injection hole is elongated and the direction perpendicular to the slit is shortened. With the shape similar to the shape of the above, almost all of the fuel ejected while spreading in a fan shape from the slit-shaped injection hole can be surely introduced into the cavity, so that the fuel injected into the cavity has the inner surface of the cylinder. Without increasing the area ratio of the cavity to the top surface of the piston,
It can definitely be reduced.

That is, according to the present invention, the adhesion of the injected fuel to the inner surface of the cylinder can be reduced without increasing the area ratio of the cavity to the top surface of the piston, and the contact area of the injected fuel with air can be increased. Therefore, there is an effect that it is possible to simultaneously improve the vaporization of the fuel and obtain a predetermined compression ratio.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention;

FIGS. 1 to 5 show a first embodiment.

In this figure, reference numeral 1 denotes a cylinder block having a cylinder 2, and reference numeral 3 denotes a cylinder head fastened to an upper surface of the cylinder block 1 so as to close the cylinder 2. A combustion chamber 4 is recessed in the cylinder 2 on the lower surface.

The cylinder head 3 has two intake ports 6 each having an intake valve 5 at an opening to the combustion chamber 4 and an exhaust valve 7 at an opening to the combustion chamber 4. Two exhaust ports 8 are provided, and a spark plug 9 is provided in a portion between the two intake valves 5 and the two exhaust valves 7, that is, in a portion substantially at the center of the cylinder 2. It is attached to look into.

Reference numeral 10 denotes a fuel injection valve which injects fuel into the cylinder 2 during an intake stroke in which the piston 11 in the cylinder 2 moves downward. The portion between the intake valves 5 in a plan view (FIG. 2) viewed from the direction of the axis 2 a of the cylinder 2 and the lower surface of the cylinder head 3 in the side view (FIG. 1). The fuel injection valve 10 is mounted so that the tip 10a of the fuel injection valve 10 can be seen inside the cylinder 2 at a position near the inner peripheral surface of the cylinder 2. The axis 10b is directed in a direction toward the center O or substantially the center of the cylinder 2 in plan view (FIG. 2), and outwardly with respect to the axis 2a of the cylinder 2 in side view (FIG. 1). It is mounted on the cylinder head 3 so as to tilt in.

The tip 10a of the fuel injection valve 10
As shown in FIGS. 4 and 5, an injection hole 10a 'for injecting fuel obliquely downward with respect to the axis 2a of the cylinder 2 is formed.
Is a slit having a rectangular cross-section having a width W and a length L, and the longitudinal direction of the slit-shaped injection hole 10a '
The center O of the cylinder 2 in the plan view (FIG. 2)
Or, it is set in a direction toward the approximate center.

On the other hand, a cavity 12 is formed in the top surface 11a of the piston 11 which reciprocates in the cylinder 2, and the ignition plug 9 is seen in the cavity 12 in the plan view (FIG. 2). The fuel is injected into the cavity 12 from the slit-shaped injection hole 10 a ′ of the fuel injection valve 10.

The cavity 11 is formed in a rectangular shape having a long side L0 in the longitudinal direction of the slit-shaped injection hole 10a 'and a short side W0 in a direction perpendicular to the long side L0 in the plan view (FIG. 2). .

In this configuration, the supply of fuel from the fuel injection valve 10 is performed during the intake stroke in which the piston 11 moves downward, by the slit-shaped injection hole 1 at the tip end thereof.
0a ′, the fuel spreads in a fan shape with a spread angle θ in a flat state having a relatively small thickness, and the top surface 1
This is done by squirting into the cavity 12 at 1a.

At this time, the cavity 12 is a rectangular spray having a long side L0 in the longitudinal direction of the slit-shaped injection hole 10a 'and a short side W0 in a direction perpendicular to the long side L0 in plan view (FIG. 2). Due to the shape similar to the shape of the fuel, almost all of the fuel ejected while spreading in a fan shape from the slit-shaped injection hole 10a 'is
It is possible to reliably prevent the fuel injected into the cavity 12 from adhering to the inner surface of the cylinder 2 without increasing the area ratio of the cavity 12 to the top surface 11a of the piston 11. Can be reduced.

Next, FIGS. 6 and 7 show a second embodiment.

In the second embodiment, the fuel injection valve 10
Like the ignition plug 9, the fuel injection valve 10 is disposed substantially at the center of the cylinder 2 in a plan view, and the fuel is injected from the fuel injection valve 10 substantially directly below.

Also in this case, the fuel injection valve 10
Is formed in a rectangular slit-shaped injection hole in the same manner as described above, and the cavity 12 in the top surface 11a of the piston 11 is also similar to the above in plan view.
The slit-shaped injection hole is formed in a rectangle having a long side L0 as a long side and a short side W0 as a direction perpendicular to the long side L0,
In the same manner as described above, almost all of the fuel ejected while spreading in a fan shape from the slit-shaped injection hole can be reliably introduced into the cavity 12, and the fuel injected into the cavity 12 adheres to the inner surface of the cylinder 2. The area ratio of the cavity 12 to the top surface 11a of the piston 11 can be reliably reduced without increasing the area ratio.

In each of the above embodiments, a protruding portion 12b is provided on the inner bottom surface 12a of the cavity 12 so as to extend in the longitudinal direction, and the fuel injected into the cavity 12 is supplied with the protruding portion 12b. Thus, while diverting into two flows toward the left and right long side surfaces 12c in the cavity 12, the left and right long side surfaces 12c are set such that the angle T with respect to the top surface 11a of the piston 11 is smaller than a right angle. By configuring the return portion so that the flow is directed inward, the fuel injected into the cavity 12 can be further reduced from adhering to the inner surface of the cylinder 2.

The present invention can be applied to a stratified combustion system.
Is not limited to a rectangular shape as viewed from the axial direction of the cylinder 2, but may be a slit-shaped injection hole 1 in the fuel injection valve 10.
Needless to say, the shape may be an elongated ellipse or an ellipse having a major axis in the longitudinal direction of 0a 'and a minor axis in a direction perpendicular to the major axis.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of a main part showing a first embodiment of the present invention.

FIG. 2 is a plan sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an enlarged cross-sectional view of a tip portion of the fuel injection valve.

FIG. 5 is a side view taken along the line VV of FIG. 4;

FIG. 6 is a vertical sectional front view of a main part showing a second embodiment of the present invention.

7 is a sectional view taken along the line VII-VII in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder 2a Cylinder axis 3 Cylinder head 4 Combustion chamber 9 Spark plug 10 Fuel injector 10a Tip of fuel injector 10a 'Injection hole 11 Piston 12 Cavity

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 61/18 320 F02M 61/18 320B 320C 330 330Z

Claims (1)

[Claims] 1. A cavity is formed in a top surface of a piston in a cylinder, and a spark plug is mounted on a cylinder head at a top of the cylinder so as to be seen in an area of the cavity when viewed from an axial direction of the cylinder. And a fuel injection valve, wherein the fuel injection valve is mounted so as to jet fuel from the injection hole at the tip end thereof into the cavity, wherein the injection hole at the tip end of the fuel injection valve is provided. Is formed into a slit-shaped injection hole having a rectangular cross-section, while the cavity is elongated in a longitudinal direction of the slit-shaped injection hole when viewed from the axial direction of the cylinder, and a direction perpendicular to the slit is shortened. A structure of an in-cylinder fuel injection type internal combustion engine, characterized in that: