JPH10339142A - Cylinder fuel injection internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform effective stratified charge combustion by holding an thick mixed gas layer in a cavity while concentrating the thick mixed gas around a spark plug at a center of a combustion chamber in a spark ignition engine in which fuel is directly injected to be supplied into a piston cavity. SOLUTION: An upper surface of a piston is formed swollen to comprise an inclined surface 1A facing an intake port 9 and an inclined surface 1B facing an exhaust port 13, a cavity 6 is formed in such a way that a main part 6A of it is opened in the intake port side inclined surface 1A to be close to a boundary L of both inclined surfaces 1A, 1B, and that only a range 6B to be on the up stream side of a spark plug to swirl is partially opened in the exhaust port side inclined surface 1B, and fuel injection is set to rise from an inner wall surface of the cavity main part 6A to be concentrated around a spark plug 3 at a center of a combustion chamber, while residual fuel is secured in the cavity 6 by an expansion part 6B to cause stratified charge combustion.

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 internal combustion engine.

[0002]

2. Description of the Related Art A conventional in-cylinder injection type internal combustion engine is disclosed, for example, in JP-A-8-35429. The purpose of this is to enable stable stratified combustion regardless of the large load range, that is, the amount of fuel injection, and the shape of the cavity (cavity) provided on the upper surface of the piston as a wall close to the spark plug And a space in which fuel and air are diffused and mixed by swirl behind the linear wall surface.
For this reason, even at the time of high load, that is, in the state of a large amount of fuel, the excess fuel does not stagnate near the spark plug,
That is, a mixture having a combustible air-fuel ratio can be formed.

[0003]

The cavity of the in-cylinder injection type internal combustion engine has a first wall section having an arc shape, a second wall section having a straight line shape, and the like. The third wall section having a circular arc shape has a continuous plane shape. The vertical section has the largest cross-sectional area near the center in the depth direction, and the second wall section is a wall section facing the third wall section. It is formed so that the height is larger than that. The upper surface of the piston is provided with a raised shape including an inclined surface facing the intake port and an inclined surface facing the exhaust port.

However, according to such a cavity shape, since most of the injected fuel spray is held in the cavity, ignition cannot be performed until the piston reaches the vicinity of top dead center, and the ignition timing is delayed from the optimum ignition timing. Therefore, sufficient output performance may not be obtained.

On the other hand, since each of the above-mentioned wall sections has a region which spreads to the exhaust side from the top of the raised shape of the piston upper surface, the injected fuel is relatively diffused to the exhaust-side region of these wall sections. As a result, the air-fuel mixture near the ignition plug becomes thin, and the ignitability may be deteriorated.

An object of the present invention is to solve such a conventional problem.

[0007]

According to a first aspect of the present invention, a spark plug is located at a substantially central portion of a combustion chamber between an intake port and an exhaust port disposed opposite to each other, and has a substantially circular shape on a top surface. A piston having a cavity formed therein, a fuel injection valve for injecting fuel from the intake port side toward the cavity, and a means for generating a swirl in the cylinder. The cavity has a protruding shape including a sloped surface facing the exhaust port and an inclined surface facing the exhaust port, and the main part of the cavity is opened in the intake port side inclined surface in the vicinity of a boundary portion between the respective inclined surfaces. Further, only the region upstream of the spark plug with respect to the swirl is formed so as to partially open into the exhaust port side inclined surface.

According to a second aspect of the present invention, in the first aspect of the invention, the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position deviated toward the intake port side from the center of the combustion chamber.

According to a third aspect of the present invention, in the first aspect of the present invention, the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position deviated toward the exhaust port side from the center of the combustion chamber.

According to a fourth aspect of the present invention, the cavity of each of the above-mentioned inventions is formed in such a manner that the main part thereof has a circular planar shape, and a portion opening into the exhaust port side inclined surface bulges from the circular shape. Shall be done.

According to a fifth aspect of the invention, the cavity of the first to third aspects of the invention has an elliptical shape whose planar shape is formed so that a major axis extends from the vicinity of the fuel injection valve to the swirl downstream direction. .

According to a sixth aspect of the present invention, the cavity of the first to third aspects of the present invention has a circular shape whose planar shape is partially projected to the inclined surface on the exhaust port side.

According to a seventh aspect of the present invention, the fuel injection valve of each of the above-mentioned inventions is provided such that the spray center thereof is directed to a protruding portion of the cavity toward the exhaust port side inclined surface.

[0014]

In each of the above inventions, part of the fuel spray injected from the fuel injection valve located on the intake port side collides with the opposing cavity inner wall surface. Since the main portion of the cavity is located on the intake port side inclined surface close to the boundary portion of the raised shape, the inner wall surface against which the fuel spray collides has the highest height up to the piston upper surface and the center of the combustion chamber. Close to the department. Therefore, the fuel spray that collides with the opposing wall surface of the cavity and rises out of the cavity concentrates near the spark plug, and forms a rich mixture layer near the spark plug. As a result, the piston can be ignited earlier than reaching the top dead center, so that good output performance is exhibited.

On the other hand, a part of the fuel spray is transported to the downstream side of the swirl by the swirl. At this time, since the cavity has a shape protruding from the exhaust port side inclined surface in the swirl downstream direction, the swirl causes the swirl. On the other hand, a large amount of fuel can be ensured in the cavity on the upstream side of the ignition plug, whereby good combustion performance can be obtained by utilizing the intake air flow in the cavity while maintaining a rich mixture layer.

According to the second aspect of the present invention, since the cavity capacity in the combustion chamber is relatively small, in an engine having a relatively large bore-stroke ratio, the dispersion of the fuel in the cavity is regulated and the stratification is achieved. , And good fuel economy performance can be secured.

According to the third aspect of the present invention, since the distance from the fuel injection valve to the opposed wall surface of the cavity is increased, the fuel vaporization time is prolonged, and unburned HC and smoke are reduced.
Another advantage is that a cavity capacity sufficient to hold fuel spray can be ensured in an engine having a relatively small bore / stroke ratio.

According to the fourth aspect of the present invention, the planar shape of the main portion of the cavity is circular, and the portion opening into the inclined surface on the exhaust port side is formed so as to bulge from the circular shape. This facilitates introduction and maintenance of the swirl into the cavity, while securing a large volume of the cavity in the swirl downstream area to hold a large amount of fuel, thereby improving the effect of improving stratified combustion.

According to the fifth aspect of the present invention, since the plane shape of the cavity is an elliptical shape whose major axis extends along the downstream direction of the swirl from the vicinity of the fuel injection valve, the flow of the entire swirl generated in the cylinder is reduced within the cavity. This facilitates the concentration of the fuel spray near the spark plug, thereby further improving the ignitability.

According to the sixth aspect of the present invention, since the planar shape of the cavity is a circular shape partially projecting from the inclined surface on the exhaust port side, the swirl in the cavity is hardly attenuated, and the fuel is transported to the vicinity of the ignition plug accordingly. Opportunity is increased, ignitability is improved, and active combustion is obtained.
Also, machining of the piston is easy.

According to the seventh aspect of the present invention, the fuel injection valve is provided so that the spray center thereof is directed to the protruding portion of the cavity toward the exhaust port side inclined surface. While adjusting the proportion of the fuel spray to be guided in the direction of the spark plug, most of the injected fuel can be reliably secured in the cavity.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show an embodiment of the present invention. First, the structure will be described. 1 is a piston, 2 is an injection valve for directly injecting fuel into a cylinder, 3 is a spark plug, 4 is a cylinder, 5 is a cylinder head, and 6 is a cavity formed on the upper surface of the piston. 7 is an intake valve,
Reference numeral 8 denotes an exhaust valve. In this embodiment, each of the intake valve 7 and the exhaust valve 8 is a four-valve type provided with two each. The ignition plug 3 is located substantially at the center of the combustion chamber 12 between the intake and exhaust valves. 9a and 9b are intake ports, 10a and 10b are intake manifolds connected to the ports 9a and 9b,
Reference numeral 11 denotes an intake control valve as a swirl generating means interposed in one intake manifold 10b, 12 denotes a combustion chamber, 13
Reference numerals a and 13b denote exhaust ports.

The intake control valve 11 is kept closed in a predetermined operating range where the load and the number of revolutions are relatively low. In this case, a swirl is generated in a counterclockwise direction in FIG.

The upper surface of the piston 1 has a slope 1A on the intake port 9a, 9b side with the boundary immediately below the spark plug 3 as a boundary.
And an inclined surface 1B on the exhaust port 13a, 13b side.

In this case, as shown in FIG. 2, the cavity 6 has a main part 6A having a circular planar shape, and the center of the circle is located substantially on the center line of the fuel spray. However, the cavity 6 has a portion (hereinafter, referred to as an “expansion portion 6B”) in which a part of the swirl downstream region swells and opens inside the exhaust port side inclined surface 1B.

During the stratified charge combustion, the fresh air is supplied to an intake port formed in a substantially linear shape so that the intake control valve 11 provided in the intake manifold 10b suppresses the introduction of fresh air from the intake port 9b during the intake stroke. 9a, the intake manifold 10a and the intake port 9
A swirl flow is generated in the cylinder 4 with the inflow resistance at a being small. The swirl in the cavity 6 is generated by the swirl flow in the cylinder being introduced into the cavity 6 during the intake and compression strokes. In addition, fuel during stratified combustion is injected by the injection valve 2 so as to face the bottom surface of the cavity 6 during the compression stroke.

Next, the operation will be described.

As shown in FIG. 2, a part of the fuel spray injected from the fuel injection valve 2 located on the intake port side collides with the opposed inner wall surface of the cavity. Main part of cavity 6
Since A is located on the intake port side inclined surface 1A close to the boundary portion (ridge line L) of the raised shape, the inner wall surface against which the fuel spray collides has the highest height up to the piston upper surface and the combustion chamber. Close to the center of 12. For this reason, the fuel spray that collides with the cavity facing wall surface and rises out of the cavity concentrates near the spark plug 3 (see the F portion in FIG. 2).
A rich mixture layer is formed near the ignition plug 3. As a result, the piston 1 can be ignited earlier than reaching the top dead center, so that it is possible to set an appropriate ignition timing and exhibit high fuel economy performance and high output unique to stratified combustion.

On the other hand, a part of the fuel spray is transported by the swirl in the downstream direction of the swirl. At this time, the cavity 6 has an expanded portion 6B protruding from the exhaust port side inclined surface 1B in the swirl downstream direction. Therefore, a large amount of fuel can be ensured in the cavity 6 on the upstream side of the spark plug 3 with respect to the swirl, and the intake air flow in the cavity 6 can be utilized while maintaining a rich mixture layer. Good combustion performance is obtained.

FIGS. 3 and 4 show the second and third embodiments of the present invention, respectively.
An embodiment will be described. FIG. 3 shows that the planar shape of the cavity 6 is an elliptical shape formed so that the long axis extends from the vicinity of the fuel injection valve 2 to the swirl downstream direction, and a part of the extended portion 6
B projecting into the exhaust port side inclined surface 1B as B,
FIG. 4 shows a plan view of the cavity 6 in which a part of the cavity 6 is formed into a circular shape with the extended portion 6B protruding from the exhaust port side inclined surface 1B.

According to the embodiment of FIG. 3, since the elliptical cavity shape extends from immediately below the fuel injection valve 2 to the swirl downstream direction, the entire swirl flow generated in the cylinder is easily introduced into the cavity 6. Thereby, the concentration of the fuel spray near the ignition plug 3 is promoted, and the ignitability can be further improved. Further, according to the embodiment of FIG. 4, since the planar shape of the cavity 6 is a circular shape partially projecting to the exhaust port side inclined surface 1B, the swirl in the cavity is hardly attenuated, and accordingly the vicinity of the spark plug 3 The opportunity for transporting fuel to the fuel cell increases, the ignitability is improved, and active combustion is obtained. There is also an advantage that machining of the piston 1 is easy.

FIGS. 5 to 7 show fourth and sixth embodiments of the present invention. The shapes of the cavities 6 are shown in FIGS. 5 and 6, respectively, and FIG. , FIG. 7 respectively correspond to those of FIG. However, in these embodiments, the ridge line L of the piston upper surface, that is, the boundary between the intake port side inclined surface 1A and the exhaust port side inclined surface 1B is defined by the combustion chamber 1
2 is different from the previous embodiment in that the position is set closer to the intake port 9 side than the center.

According to these embodiments, since the capacity of the cavity 6 in the combustion chamber 12 is relatively small, the bore
In an engine having a relatively large stroke ratio, the dispersion of fuel in the cavity 6 can be regulated, and the stratification of the air-fuel mixture can be maintained to ensure good fuel economy.

FIGS. 8 to 10 show seventh to ninth embodiments of the present invention. The shapes of the cavities 6 are shown in FIG. 8 and FIG. 3, respectively. , FIG.
Respectively correspond to those in FIG. However, these embodiments are different from the preceding embodiments in that the ridge line L on the upper surface of the piston is set at a position closer to the exhaust port 13 side than the center of the combustion chamber 12.

According to these embodiments, the fuel injection valve 2
Therefore, the effect that the fuel vaporization time from injection to collision with the cavity wall surface is prolonged and unburned HC and smoke are reduced accordingly can be expected. Another advantage is that a cavity capacity sufficient to hold fuel spray can be ensured in an engine having a relatively small bore / stroke ratio.

In each of the above embodiments, the direction of the fuel injection valve 2 is adjusted so that the spray center is
B can be set to point. This allows
While adjusting the proportion of the fuel spray to be guided toward the spark plug 3 by colliding with the wall surface of the cavity main portion 6A, most of the injected fuel can be reliably secured in the cavity 6 to enhance the effect of stratified combustion.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a first embodiment of a direct injection engine according to the present invention.

FIG. 2 is a plan view of a piston according to the first embodiment.

FIG. 3 is a plan view of a piston according to a second embodiment of the present invention.

FIG. 4 is a plan view of a piston according to a third embodiment of the present invention.

FIG. 5 is a plan view of a piston according to a fourth embodiment of the present invention.

FIG. 6 is a plan view of a piston according to a fifth embodiment of the present invention.

FIG. 7 is a plan view of a piston according to a sixth embodiment of the present invention.

FIG. 8 is a plan view of a piston according to a seventh embodiment of the present invention.

FIG. 9 is a plan view of a piston according to an eighth embodiment of the present invention.

FIG. 10 is a plan view of a piston according to a ninth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 piston 1A intake port side inclined surface 1B exhaust port side inclined surface 2 fuel injection valve 3 spark plug 4 cylinder 5 cylinder head 6 cavity 6A main cavity 6B cavity extension 7 intake valve 8 exhaust valve 9a, 9b intake port 10a, 10b Intake manifold 11 Intake control valve 12 Combustion chamber 13a, 13b Exhaust port L Boundary of slope (ridgeline)

Claims (7)

[Claims] A piston having a substantially circular cavity formed on a top surface thereof, a piston located at a substantially central portion of a combustion chamber between an intake port and an exhaust port disposed opposite to each other; An internal combustion engine comprising: a fuel injection valve for injecting fuel from the cavity toward the cavity; and a means for generating a swirl in the cylinder, wherein a piston upper surface has an inclined surface facing an intake port and an inclined surface facing an exhaust port. And the cavity has a main portion which is opened in the intake port side inclined surface in the vicinity of a boundary portion between the inclined surfaces.
And so that only the region on the upstream side of the spark plug with respect to the swirl partially opens into the exhaust port side inclined surface,
An in-cylinder fuel injection type internal combustion engine characterized by being formed. 2. The in-cylinder fuel injection according to claim 1, wherein the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position deviated toward the intake port side from the center of the combustion chamber. Type internal combustion engine. 3. The in-cylinder fuel injection according to claim 1, wherein the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position deviated toward the exhaust port side from the center of the combustion chamber. Type internal combustion engine. 4. The cavity according to claim 1, wherein a main portion thereof has a circular planar shape, and a portion that opens into the exhaust port-side inclined surface is formed in a manner bulging from the circular shape. An in-cylinder fuel injection type internal combustion engine according to any one of claims 1 to 3. 5. The cavity according to claim 1, wherein a plane shape of the cavity is an elliptical shape formed such that a major axis extends from a vicinity of the fuel injection valve to a swirl downstream direction. 8. The in-cylinder fuel injection internal combustion engine according to item 1. 6. The in-cylinder fuel injection according to any one of claims 1 to 3, wherein the cavity has a planar shape that is partially circular and protrudes from the inclined surface on the exhaust port side. Type internal combustion engine. 7. The fuel injection valve according to claim 1, wherein a spray center of the fuel injection valve is provided so as to point to a protruding portion of the cavity toward the inclined surface on the exhaust port side.
The in-cylinder fuel injection type internal combustion engine according to any one of the above.