JPH08177500A - Direct injection spark ignition engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To promote the mixing of fuel that collides with the piston in a direct injection spark ignition engine. In a direct-injection spark ignition engine in which a spark plug 8 and a fuel injection valve 3 are exposed to a combustion chamber 2, a diffusion table 12 that rises from a top surface 11 of a piston 1 is formed, and the diffusion table 12 is formed along a fuel injection direction. To form an inclined guide surface 13.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A premixed spark ignition engine having a carburetor and a fuel injection valve in an intake pipe has a problem that output characteristics and exhaust composition are deteriorated due to fuel transportation delay, especially during transient operation. In order to solve this, a direct injection spark ignition engine in which a fuel injection valve is exposed to the combustion chamber to directly inject fuel into the combustion chamber has been considered (actual application 1
-173416 gazette, reference).

As a conventional direct injection type spark ignition engine, there is one shown in FIG. 7, for example.

To explain this, the fuel injection valve 3 is arranged on the ceiling wall of the combustion chamber of the cylinder head 10 so as to face the top surface 11 of the piston 1 from the side of the combustion chamber.

In FIG. 7, L is the center line of the fuel spray injected from the injection port of the fuel injection valve 3. The fuel spray center line L is arranged so as to be inclined with respect to the top surface 11 of the piston 1 at a predetermined angle θ ₀ . The piston top surface 11 is formed along a substantially horizontal plane A orthogonal to the cylinder axis.

In the compression stroke in which the piston 1 rises, the fuel spray injected from the injection port of the fuel injection valve 3 hits the piston top surface 11 and is reflected to mix with the air in the combustion chamber 2.

The spark plug 8 blows a spark near the top dead center of the piston 1 to ignite the compressed mixture and burn the mixture.

[0008]

However, in such a conventional direct injection spark ignition engine, in the compression stroke in which the piston 1 rises, a part of the fuel spray colliding with the piston top surface 11 is generated by the piston. The fuel adheres to the top surface 11 and diffuses and burns the fuel on the piston 1 to generate smoke.

The fuel spray having the velocity V is the top surface 1 of the piston.
The velocity component VH _{0 in the} direction normal to the collision surface at the moment of collision with 1 is expressed as VH ₀ = Vsin θ ₀ (2).

If the velocity component VH ₀ is large, the residual rate of the fuel adhering to the piston 1 in the fuel spray impinging on the piston 1 increases, and the amount of smoke generated increases.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and promote mixing of fuel that collides with a piston in a direct injection spark ignition engine.

[0012]

A direct-injection spark ignition engine according to claim 1 is a direct-injection spark ignition engine in which a spark plug and a fuel injection valve are exposed to a combustion chamber. Of the piston, a diffusion base protruding from the top face of the piston is formed, and a guide surface inclined along the fuel injection direction is formed on the diffusion base.

According to a second aspect of the present invention, in the direct injection type spark ignition engine of the first aspect, the shape of the fuel spray injected from the fuel injection valve is a conical column shape, and the guide surface is along the fuel injection direction. To form a slanted flat surface.

According to a third aspect of the present invention, there is provided a direct injection spark ignition engine according to the first aspect of the invention, wherein the fuel spray injected from the fuel injection valve is formed into a hollow conical cylinder shape, and the guide surface is fuel-injected. Inclined along the direction and curved in a crescent shape.

According to a fourth aspect of the present invention, in the direct injection type spark ignition engine, the diffusion table is raised in a spherical shape.

[0016]

In the direct-injection spark ignition engine according to the first aspect, the fuel spray injected from the fuel injection valve hits the guide surface of the diffusion table and mixes with the air in the combustion chamber. When the spark plug blows a spark to the mixture, the mixture ignites and burns.

Since the guide surface of the diffusion table is inclined along the fuel injection direction, the velocity component in the direction normal to the surface with which the fuel spray collides is reduced, and the fuel spray reflects on the guide surface and enters the combustion chamber. Promote spreading.

As a result, it is possible to reduce the residual rate of the fuel adhering to the piston of the fuel spray impinging on the guide surface, and to reduce the amount of smoke generated by the diffuse combustion of the fuel on the piston.

Further, the diffusion table raised from the top surface of the piston absorbs combustion heat and becomes higher in temperature than other parts, so that evaporation of fuel adhering to the diffusion table is promoted and the amount of smoke generated is reduced. can do.

In the direct injection spark ignition engine according to the second aspect of the present invention, most of the fuel spray injected from the fuel injection valve and spreading in the shape of a conical column can collide with the flat guide surface, and the fuel is guided. It reflects on the surface and promotes spreading to the combustion chamber.

In the direct-injection spark ignition engine according to the present invention, the fuel spray injected from the fuel injection valve and spreading in the shape of a hollow conical cylinder is caused to collide with a crescent-shaped curved guide surface, and the fuel is reflected on the guide surface. And promote the spread to the combustion chamber.

In the direct-injection spark ignition engine according to the fourth aspect, the spherically raised diffusion table does not have a sharp portion having a large surface area, so that a heat spot is generated even when exposed to high-temperature combustion gas. This can be prevented and the heat resistance of the piston can be increased.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a 4-stroke engine will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a spark plug 8 faces the center of the combustion chamber 2, and two intake valves and two exhaust valves are provided so as to face each other so as to sandwich the spark plug 8. 6 in the figure
Is an intake port, and 7 is an exhaust port.

A fuel injection valve 3 is provided on the ceiling wall of the combustion chamber of the cylinder head 10 from the side of the combustion chamber 2 to the top surface 11 of the piston 1.
Is arranged so as to face. The fuel injection valve 3 faces the combustion chamber 2 beside the two intake valves and in the middle of the two intake valves.

The fuel injection timing from the fuel injection valve 3 is set so that the fuel injection pressure does not rise above the pressure in the combustion chamber 2 during the compression stroke in which the piston 1 rises.

In FIG. 1, L is the center line of the fuel spray injected from the fuel injection valve 3. This fuel spray center line L
Are arranged so as to be inclined at a predetermined angle θ ₀ with respect to the top surface 11 of the piston 1. The piston top surface 11 is formed along a substantially horizontal plane A orthogonal to the cylinder axis.

In this embodiment, the fuel spray injected from the fuel injection valve 3 is in the form of a conical column from the single injection port toward the piston top surface 11.

The piston 1 is integrally formed with a diffusion table 12 which is raised from the top surface 11 of the piston 1 on the center line L of the fuel spray. The diffusion table 12 has a guide surface 13 on which the fuel spray injected from the fuel injection valve 3 collides.

In this embodiment, the guide surface 13 is formed in a flat shape which is inclined along the fuel spray center line L. That is, the angle θ _{1 at} which the guide surface 13 is inclined with respect to the fuel spray center line L is formed to be smaller than the angle θ _{0 at} which the piston top surface 11 is inclined with respect to the fuel spray center line L.

As shown in FIG. 2, the guide surface 13 is formed in a rectangular shape. The diffusion table 12 is formed by a guide surface 13 and a plurality of flat surfaces that connect the periphery of the guide surface 13 and the piston top surface 11.

Next, the operation will be described.

In the compression stroke in which the piston 1 rises, the fuel spray injected from the injection port of the fuel injection valve 3 spreads in a conical column shape centered on the fuel spray center line L, and most of it is the guide surface of the diffusion table 12. Upon hitting 13, the piston 1 mixes with the air in the combustion chamber 2 before reaching the top dead center.

The spark plug 8 emits sparks near the top dead center of the piston 1 to ignite the compressed air-fuel mixture and burn the air-fuel mixture.

In the compression stroke in which the piston 1 rises, most of the fuel spray that collides with the guide surface 13 is reflected by the inclined diffusion table 12 and spreads into the combustion chamber 2. Since the guide surface 13 is inclined along the fuel spray center line L, it is possible to reduce the residual rate of the fuel that adheres to the piston 1 in the fuel spray that collides with the guide surface 13.

The velocity component VH _{1 in the} direction normal to the colliding surface at the moment when the fuel spray having the velocity V collides with the guide surface 13 is expressed as VH ₁ = Vsin θ ₁ (1)

On the other hand, the velocity component VH _{0 in the} direction normal to the collision surface at the moment when the fuel spray having the velocity V collides with the piston top surface 11 is expressed as VH ₀ = Vsin θ ₀ (2) It

Since the guide surface 13 is inclined along the fuel spray center line L and θ ₁ is smaller than θ ₀ , the fuel spray guide surface 1
The velocity component VH _{1 in the} normal direction with respect to 3 is smaller than the velocity component VH _{0 with} respect to the piston top surface 11 of the conventional device, and the residual rate of the fuel adhering to the piston 1 in the fuel spray colliding with the guide surface 13 is reduced. You can

By reducing the amount of fuel adhering to the piston 1, it is possible to reduce the amount of smoke produced by the diffuse combustion of the fuel on the piston 1.

Further, the diffusion table 12 raised from the piston top surface 11 absorbs combustion heat and becomes higher in temperature than other parts of the piston 1, so that evaporation of the fuel adhering to the diffusion table 12 is promoted, The amount of smoke generated can be reduced.

Next, another embodiment shown in FIG. 3 will be described. It should be noted that the same parts as those in FIG.

In this embodiment, the fuel spray injected from the fuel injection valve 3 is in the form of a hollow conical cylinder extending from the single injection port toward the piston top surface 11.

As shown in FIG. 4, the diffusion table 22 is formed by bulging from the piston top surface 11 in a crescent shape.
Has a guide surface 23 for colliding the fuel spray injected from the fuel injection valve 3.

The guide surface 23 is such that the fuel spray is the top surface 11 of the piston.
It is formed in a crescent shape along an annular portion reaching to.

The guide surface 23 is formed into a curved surface which is inclined along the fuel spray center line L at a substantially constant angle θ ₂ .
Angle θ at which the guide surface 23 is inclined with respect to the fuel spray center line L
₂ is formed so as to be smaller than an angle θ _{0 at} which the piston top surface 11 is inclined with respect to the fuel spray center line L.

Next, the operation will be described.

In the compression stroke in which the piston 1 rises, the fuel spray injected from the injection port of the fuel injection valve 3 spreads in the shape of a conical cylinder, and a part of the fuel spray hits the guide surface 23 of the diffusion table 22,
Mix with the air in the combustion chamber 2.

In the compression stroke in which the piston 1 rises, most of the fuel spray that collides with the guide surface 23 is reflected by the inclined guide surface 23 and spreads to the combustion chamber 2. Since the guide surface 23 is inclined along the fuel spray center line L, the residual rate of the fuel adhering to the piston 1 in the fuel spray colliding with the guide surface 23 can be reduced.

The velocity component VH _{2 in the} direction normal to the colliding surface at the moment when the fuel spray having the velocity V collides with the guide surface 23 is expressed as VH ₂ = Vsin θ ₂ (3).

The velocity component VH ₂ of the fuel spray in the direction normal to the guide face 23 becomes smaller than the velocity component VH _{0 with} respect to the piston top face 11 of the conventional apparatus, and the fuel spray that collides with the guide face 23 adheres to the piston 1. The residual rate of fuel consumption can be reduced.

Next, another embodiment shown in FIG. 5 will be described. It should be noted that the same parts as those in FIG.

In this embodiment, the fuel spray injected from the fuel injection valve 3 spreads in a conical column shape from the single injection port toward the piston top surface 11.

As shown in FIG. 6, the diffusion table 32 is formed by projecting spherically from the piston top surface 11.

The diffusion table 32 has a spherically curved guide surface 33.
Have. The part of the guide surface 33 where the fuel spray collides is
It is formed in a curved surface inclined along the fuel spray center line L.

Next, the operation will be described.

In the compression stroke in which the piston 1 rises, most of the fuel spray injected from the injection port of the fuel injection valve 3 and spreading in a conical column shape spreads over a wide area by hitting the guide surface 33 having a spherical shape, and inside the combustion chamber 2. Mix with air.

During the compression stroke in which the piston 1 rises, most of the fuel spray that collides with the guide surface 33 is reflected by the inclined guide surface 33 and spreads to the combustion chamber 2, and the residual rate of fuel adhering to the piston 1 Can be reduced.

Further, since the spherically raised diffusion table 32 does not have a sharp portion having a large surface area, it is possible to prevent the generation of heat spots even when exposed to high temperature combustion gas, and the heat resistance of the piston 1 is improved. Can be increased.

[0059]

As described above, in the direct injection spark ignition engine according to the first aspect of the present invention, the fuel injection direction of the fuel injection valve is directed to the top surface of the piston, and the diffusion table protruding from the top surface of the piston is formed. Since the guide surface that is inclined along the fuel injection direction is formed on the diffusion table, mixing of the fuel that collides with the piston with air is promoted, and the occurrence of smoke and the like can be suppressed.

In the direct injection type spark ignition engine described in claim 2, in the invention described in claim 1, the form of the fuel spray injected from the fuel injection valve is made into a conical column shape, and the guide surface of the diffusion table is injected with the fuel. Since the fuel spray is formed in a flat shape that is inclined along the direction, most of the fuel spray can be made to collide with the flat guide surface, and the fuel is reflected on the guide surface and promoted to spread to the combustion chamber.

According to the third aspect of the present invention, in the direct injection type spark ignition engine according to the first aspect of the invention, the form of the fuel spray injected from the fuel injection valve is made into a hollow conical cylinder shape, and the guide surface of the diffusion table is formed. Since it is inclined along the fuel injection direction and curved in a crescent shape, the fuel is reflected on the guide surface and promoted to spread to the combustion chamber.

The direct-injection spark ignition engine according to a fourth aspect of the present invention is the same as the first aspect of the present invention, in which the diffusion table is raised in a spherical shape, so that it does not have a sharp portion having a large surface area and is exposed to high-temperature combustion gas. Even if this happens, heat spots can be prevented from occurring and the heat resistance of the piston can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an engine showing an embodiment of the present invention.

FIG. 2 is a view showing the shape of a piston.

FIG. 3 is a sectional view of an engine showing another embodiment.

FIG. 4 is a view showing the shape of a piston.

FIG. 5 is a sectional view of an engine showing still another embodiment.

FIG. 6 is a view showing the shape of a piston.

FIG. 7 is a sectional view of an engine showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Combustion chamber 3 Fuel injection valve 6 Intake port 7 Exhaust port 8 Spark plug 10 Cylinder head 11 Piston top surface 12 Diffusion table 13 Guide surface 22 Diffusion table 23 Guide surface 32 Diffusion table 33 Guide surface

Claims (4)

[Claims] 1. A direct injection type spark ignition engine in which a spark plug and a fuel injection valve are faced to a combustion chamber, the fuel injection direction of the fuel injection valve is directed to the top surface of the piston, and a diffusion table protruding from the top surface of the piston is formed. The direct injection spark ignition engine is characterized in that the diffusion table is formed with a guide surface inclined along the fuel injection direction. 2. The direct injection according to claim 1, wherein the shape of the fuel spray injected from the fuel injection valve is made into a conical columnar shape, and the guide surface is formed into a flat surface inclined along the fuel injection direction. Jet spark ignition engine. 3. The fuel spray injected from the fuel injection valve has a hollow conical tubular shape, and the guide surface is inclined along the fuel injection direction and curved in a crescent shape. Item 1. A direct injection spark ignition engine according to Item 1. 4. The direct injection spark ignition engine according to claim 1, wherein the diffusion table is raised in a spherical shape.