JPH11210469A - Cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of smoke and soot from a spark plug in a cylinder injection type spark ignition engine adapted to carry out stratified combustion. SOLUTION: In a cylinder injection type spark ignition engine including a spark plug 8 provided at the center of the upper part of a cylinder, a fuel injection valve 5 provided in the peripheral part of the cylinder, a recessed groove 1 formed in the top surface of a piston 4, and a swirl flow creating means provided in an intake pipe, a convex part 13 having inclined surfaces 13a, 13c and a vertical surface 13b are formed on the exhaust pipe side of the recessed groove 1. During the later half period of compression stroke, fuel is injected into the recessed groove 1, striding over the vertical surface 13b of the convex part 13. With this arrangement, fuel injected onto the top surface of the convex part 13, creates a mixture which can be easily ignited around the spark plug, and fuel injected toward an intake pipe from the convex part is diffused in the recessed groove 1, thereby it is possible to prevent occurrence of smoke and soot from the spark plug.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection spark ignition engine for reducing smoldering of an ignition plug and exhaust emission during stratified charge combustion.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine, an in-cylinder injection system for directly injecting fuel into a cylinder has been attracting attention for the purpose of improving fuel efficiency and reducing pollution of exhaust gas. FIG. 19 shows a configuration diagram of a typical direct injection engine. In this system, the spark plug 8 is usually arranged at the center of the upper part of the cylinder 6, and the concave portion 1 is provided at the top of the piston 4 on the side of the intake pipes 9a and 9b. The position of the exhaust pipe side wall surface 1 a of the concave groove 1 is installed below the ignition plug 8. The fuel injection valve 5 is installed on the intake pipe side above the cylinder 6. A swirl control valve 2 is provided on the intake pipe 9b.
This valve can be opened and closed by a drive mechanism (not shown) according to the load of the engine. When the engine load is low load or medium load, the swirl control valve 2 is closed by the drive mechanism, and air is introduced into the cylinder 6 only from the intake pipe 9a during the intake stroke. A swirling flow occurs. In the latter half of the compression stroke, fuel atomized to a number of diameters + μm from the fuel injection valve 5 is injected into the concave groove 1. The fuel injection amount at this time is approximately 1/25 to 1 /
50. The fuel rotates in the groove 1 while being vaporized by the action of the swirling flow, and is carried near the spark plug 8. As a result, an air-fuel mixture having a relatively high fuel concentration is formed around the ignition plug, and even a lean air-fuel mixture having an average air-fuel ratio of 25 to 50 can be stably ignited and burned. An in-cylinder injection spark ignition engine of this type is disclosed in, for example,
No. 4416, JP-A-5-18245 and JP-A-5-256137.

[0003]

By the way, in such a direct injection type spark ignition engine, fuel is injected late in the compression stroke at the time of low load or medium load operation, so that the fuel vaporization time is short, and the ignition timing is low. In order to obtain a sufficiently vaporized mixture, very finely atomized fuel must be supplied into the cylinder. Further, since the injection period of the fuel needs to be as short as possible, the injection speed of the fuel is higher than that of the conventional port injection system. In this case, the mixture with the air is not sufficiently mixed, and the mixture having a very high fuel concentration reaches the vicinity of the spark plug, and the controllability of the ignition timing is deteriorated, and the smolder and soot of the spark plug occur. There is fear.

[0004]

In order to overcome the above-mentioned problems, in a first direct injection type spark ignition engine according to the present invention, a side wall surface of an exhaust pipe of a concave groove of a piston is positioned below a spark plug and an intake pipe. The side wall surface is disposed below the fuel injection valve, and a convex portion is provided on the bottom surface of the concave groove on the exhaust pipe side. The intake pipe side of the convex portion is a vertical wall surface, and the upstream and downstream sides of the swirl flow of the convex portion are formed by slopes smoothly connected to the concave grooves. In the latter half of the compression stroke during low-load and medium-load operation, the injection direction of the fuel injector is determined so as to straddle the intake pipe side wall surface of the projection.

In the second direct injection type spark ignition engine of the present invention, the exhaust pipe side wall surface of the concave groove of the piston is disposed below the ignition plug, and the intake pipe side wall surface is disposed below the fuel injection valve. A convex portion is provided on the bottom surface of the concave groove on the intake pipe side. The upstream and downstream sides of the swirling flow of the convex portion are formed by slopes that smoothly connect to the concave grooves. In the latter half of the compression stroke during low-load and medium-load operation, the injection direction of the fuel injection valve is determined so as to straddle the boundary between the exhaust side of the projection and the groove.

In the third direct injection type spark ignition engine of the present invention, the side wall surface of the exhaust pipe in the groove of the piston is disposed below the ignition plug, and the side wall surface of the intake pipe is disposed below the fuel injection valve. A convex portion is provided on the bottom surface of the concave groove on the intake pipe side. The upstream and downstream sides of the swirling flow of the convex portion are formed by slopes that smoothly connect to the concave grooves. A structure is provided on the exhaust pipe side of the projection to block the flow of air near the surface of the projection from the intake pipe side to the exhaust pipe side. In the latter half of the compression stroke during low-load and medium-load operation, the injection direction of the fuel injection valve is determined so as to straddle the boundary between the exhaust side of the projection and the groove.

In a fourth direct injection type spark ignition engine according to the present invention, the exhaust pipe side wall surface of the concave groove of the piston is disposed below the ignition plug, and the intake pipe side wall surface is disposed below the fuel injection valve. A concave portion is provided on the bottom surface of the concave groove on the intake pipe side. The upstream side and the downstream side of the swirling flow of the concave portion are constituted by slopes smoothly connected to the concave groove. In the latter half of the compression stroke during low-load and medium-load operation, the injection direction of the fuel injector is determined so as to straddle the boundary between the exhaust side of the recess and the groove.

In the fifth direct injection type spark ignition engine of the present invention, the exhaust pipe side wall surface of the concave groove of the piston is disposed below the ignition plug, and the intake pipe side wall surface is disposed below the fuel injection valve. The injection direction of the injection valve is determined so that the fuel injected late in the compression stroke is directed to the bottom of the groove. Means are provided for generating a flow in which fuel rising in the direction of the spark plug along the groove wall circulates about an axis parallel to the central axis of the cylinder and perpendicular to a plane passing through the spark plug and the fuel injection valve.

In the above-described first in-cylinder injection spark ignition engine, during a low-load or medium-load operation, in the latter stage of the compression stroke, the intake pipe side wall surface of the convex portion provided on the exhaust pipe side of the concave groove of the piston is removed. Fuel is injected from the fuel injection valve to straddle. The fuel injected toward the upper surface of the projection is transported to the vicinity of the spark plug while being vaporized by the swirling flow around the cylinder axis. on the other hand,
The fuel injected toward the intake pipe side from the projection collides with the intake pipe side wall surface of the projection along the bottom surface of the groove, where it flows toward the upstream and downstream sides of the swirling flow and is widely dispersed in the groove. I do. As a result, it is possible to prevent generation of an air-fuel mixture with an excessively high fuel concentration around the ignition plug.

In the above-described second in-cylinder injection type spark ignition engine, at the latter stage of the compression stroke during low load or medium load operation, the convex portion provided on the intake pipe side of the concave groove of the piston at the exhaust pipe side. The fuel is injected from the fuel injection valve so as to straddle the boundary between the groove and the bottom of the groove. The fuel injected toward the exhaust pipe side of the concave groove is conveyed to the vicinity of the ignition plug while being vaporized by the swirling flow around the cylinder axis. On the other hand, the fuel injected into the convex portion is divided into an upstream side and a downstream side of the swirling flow and widely dispersed in the concave groove. As a result, it is possible to prevent generation of an air-fuel mixture with an excessively high fuel concentration around the ignition plug.

The third in-cylinder injection spark ignition engine described above has the same operation as the second in-cylinder injection spark ignition engine described above, and furthermore, the vicinity of the surface of the projection is changed from the intake pipe side to the exhaust pipe. The fuel vapor flowing toward the side is dispersed on the upstream side and the downstream side of the swirling flow by the flow shielding structure provided on the exhaust pipe side of the projection, and an air-fuel mixture with an excessively high fuel concentration is generated in the ignition plug. Can be prevented.

In the above-described fourth in-cylinder injection spark ignition engine, at the latter stage of the compression stroke during low load or medium load operation, the exhaust pipe side of the concave portion provided on the intake pipe side of the concave groove of the piston is connected. Fuel is injected from the fuel injection valve so as to straddle the boundary of the groove bottom. The fuel injected toward the exhaust pipe side of the concave groove is conveyed to the vicinity of the ignition plug while being vaporized by the swirling flow around the cylinder axis. On the other hand, the fuel injected into the concave portion is divided into the upstream side and the downstream side of the swirling flow and widely dispersed in the concave groove. As a result, it is possible to prevent generation of an air-fuel mixture with an excessively high fuel concentration around the ignition plug.

In the above-described fifth in-cylinder injection spark ignition engine, fuel is injected from the fuel injection valve toward the concave groove of the piston at the latter stage of the compression stroke during low load or medium load operation. The fuel in the groove rises toward the spark plug along the wall of the groove while being vaporized by the swirling flow around the cylinder axis, and is parallel to the central axis of the cylinder and perpendicular to the plane passing through the spark plug and the fuel injection valve. Circulate around. This promotes the mixing of fuel and air below the spark plug, suppresses the flow from the piston toward the spark plug, and prevents the formation of an excessively rich fuel-air mixture around the spark plug. it can.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view showing a first embodiment of a direct injection type spark ignition engine according to the present invention, FIG. 2 is a schematic plan view thereof, and FIG. 3 is a sectional view taken along line AA in FIG. FIG. As shown in FIG. 19, the general configuration of the engine is such that two intake pipes 9a and 9b and two exhaust pipes 10 are provided.
Is provided above the cylinder 6, and is a four-valve engine in which an intake valve 11 and an exhaust valve 12 are provided in each intake pipe and exhaust pipe. The swirl control valve 2 is provided in the intake pipe 9b. The swirl control valve is closed by a drive mechanism (not shown) at the time of low load or medium load operation, and is opened at the time of high load operation. An ignition plug 8 is provided above the center of the cylinder 6, and a fuel injection valve 5 is provided between the intake pipes 9a and 9b. The fuel injection valve 5 atomizes the fuel to a size of several tens of μm and injects it into the cylinder 6 in a conical shape. A circular concave groove 1 is provided near the intake pipe side of the top surface of the piston 4. The exhaust pipe side wall surface 1a of the concave groove 1 is formed by a slope that forms an obtuse angle with respect to the concave groove bottom surface, and the other side surface of the concave groove 1 is substantially perpendicular to the concave groove bottom surface. In the present invention, as shown in FIGS.
The convex portion 13 is provided on the 0 side. The intake pipe side wall surface 13b of the convex portion 13 is substantially at the center of the concave groove and forms an angle substantially perpendicular to the concave groove bottom surface. On the other hand, the side surface 1 of the projection 13
3a and 13c are connected to the bottom surface of the groove 1 by a gentle slope. The exhaust pipe side of the projection 13 is connected to the exhaust pipe side wall surface 1 a of the concave groove 1. Also, the protrusion 13
Is a flat surface. As shown in FIG. 4, the fuel injection direction of the fuel injection valve 5 is such that the conical fuel spray 14 injected from the fuel injection valve 5 in the latter stage of the compression stroke straddles the intake pipe side wall surface 13 b of the projection 13. , And is supplied to both the upper surface of the convex portion 13 and the bottom surface of the concave groove 1 on the intake pipe side.

In this embodiment, during low load and medium load operation, the swirl control valve 2 is closed, and air is introduced into the cylinder 6 from the intake pipe 9a. As a result, a swirling flow around the axis of the cylinder is generated in the cylinder 6. In the vicinity of the surface of the piston, this swirling flow becomes a flow S that swirls in the concave groove 1 on the top surface of the piston as shown in FIG. Since the side surface (wall surface) 13a corresponding to the upstream side of the swirling flow and the side surface (wall surface) 13c corresponding to the downstream side of the convex portion 13 are gently inclined from the bottom surface of the concave groove 1, the disturbance of the swirling flow S due to the convex portion 13 is small. In the latter half of the compression stroke, the swirling flow S continues to exist in the groove 1 without disappearing.

In the latter stage of the compression stroke following the intake, the fuel injection valve 5 straddles the intake pipe side wall surface 13b of the projection 13 toward the upper surface of the projection 13 and the bottom surface of the groove 1 on the intake pipe side. The fuel is injected in an amount of 1/25 to 1/50 of the intake air mass. As shown in FIG. 5, the fuel F1 injected toward the upper surface of the projection 13 evaporates while passing through the groove 1 toward the exhaust pipe due to the inertia force at the time of injection, and is swirled by the swirling flow S. And arrives near the center of the cylinder.
On the other hand, a part F21 of the fuel injected toward the intake pipe side from the intake pipe side wall surface 13b of the convex portion 13 advances toward the exhaust pipe side near the bottom surface of the concave groove 1 due to inertia force at the time of injection while evaporating. Collides with the intake pipe side wall surface 13b of the projection. Since the intake pipe side wall surface 13b of the convex portion is perpendicular to the bottom surface of the concave groove 1, the fuel F21 colliding with this wall surface decelerates over the wall surface 13b while decelerating, and passes through the upper surface of the convex portion 13 to the cylinder 6
To the vicinity of the center of. Also, the side wall surface of the intake pipe of the projection 13
Part of fuel injected toward intake pipe side from 13b F22
Moves toward the exhaust pipe near the bottom surface of the concave groove 1 due to the inertia force at the time of injection while evaporating, and the intake pipe side wall surface 13b of the convex portion
Collide with The fuel F22 colliding with the wall surface decelerates over the wall surface 13b while decelerating, reaches a side surface (wall surface) 13c corresponding to the downstream side of the swirling flow of the projection 13, and further descends on the wall surface 13c by the swirling flow S to form the groove 1 Head toward the intake pipe.

FIG. 6 shows the above vapor behavior in a longitudinal section. Fuel F1 injected toward the upper part of the projection 13
Quickly reaches the vicinity of the electrode position of the spark plug 8, a mixture having a high fuel concentration is generated near the ignition plug, and the mixture can be reliably ignited. On the other hand, the fuel F21 injected toward the intake pipe side of the concave groove 1 collides with the intake pipe side wall surface of the convex part, so that the velocity toward the exhaust pipe side is greatly reduced, and the fuel F21 is injected into the upper part of the convex part 1. It moves toward the center of the cylinder later than the fuel F1 injected toward the cylinder. As a result, the fuel vapor directed toward the ignition plug 8 has a long band-like distribution as shown by F in FIG. Also, as shown in FIG.
A part of the fuel injected toward the intake pipe side is not directed to the center of the cylinder, but is diffused toward the intake pipe side of the concave groove 1 by the swirling flow. Lower. On the other hand, in the case of the conventional method in which the convex portion 13 is not provided and the bottom surface of the concave groove 1 is flat, almost all of the fuel injected toward the bottom surface of the concave groove 1 has a short time as shown in FIG.
Reaches the electrode section. As a result, the steam has a locally concentrated distribution near the spark plug as shown by F 'in FIG. FIG. 8 shows a change in the fuel-air ratio of the air-fuel mixture near the electrode portion of the spark plug with respect to the crank angle. In the conventional method, since the concentrated steam reaches the electrode portion of the ignition plug, the fuel-air ratio rapidly increases with time and greatly exceeds the stoichiometric mixture ratio. Further, as the fuel gas approaches the top dead center, the concentrated steam passes through the electrode portion of the spark plug, and the fuel-air ratio decreases rapidly. In general, the combustion speed is highest near the stoichiometric mixture ratio, so to improve ignitability and subsequent flame propagation, it is desirable to ignite when the mixture near the spark plug has the stoichiometric mixture ratio. On the other hand, in the conventional method, since the fuel-air ratio in the vicinity of the ignition plug changes rapidly as shown in FIG. 8, it is very difficult to control the ignition timing. Also, if ignition is delayed for any reason, a highly concentrated air-fuel mixture is generated at the electrode portion of the spark plug, which may cause smoldering and soot of the spark plug. On the other hand, in the present invention, since the steam toward the spark plug has a band-like distribution, and the diffusion of the steam into the concave groove is promoted by the projection, the fuel-air ratio of the air-fuel mixture around the spark plug is as shown in FIG. And gradually changes with respect to the crank angle. For this reason, there is an effect that the control of the ignition timing is facilitated and the occurrence of smoldering and soot of the spark plug can be prevented.

FIG. 9 is a longitudinal sectional view showing a second embodiment of the direct injection type spark ignition engine according to the present invention, FIG. 10 is a schematic plan view thereof, and FIG. 11 is a sectional view taken along line A--A in FIG. It is sectional drawing seen from the side. The schematic configuration of the present engine is the same as that of the first embodiment, and differs from the first embodiment only in the shape of the protrusion 13 provided in the concave groove 1 and the injection direction of the fuel injection valve 5. In this embodiment, as shown in FIGS.
3 is provided on the intake pipe side of the concave groove 1. The cross section of the convex portion 13 has a triangular shape as shown in FIG. 11, and the side surfaces 13a and 13c have a gentle slope with respect to the bottom surface of the concave groove 1.

In this embodiment, at the time of low load and medium load operation, the swirl control valve is closed as in the first embodiment, and a swirling flow around the cylinder axis is generated in the cylinder. Since the side surfaces 13a and 13c of the convex portion are gently inclined with respect to the bottom surface of the concave groove 1, the turbulence of the swirl flow S due to the convex portion 13 is small, and the swirl flow S does not disappear even in the latter stage of the compression stroke. It remains in the groove 1.

In the latter stage of the compression stroke following the intake air, the intake air flows from the fuel injection valve 5 across the exhaust pipe side wall 13d of the projection 13 toward the bottom of the projection 13 and the groove 1 on the exhaust pipe side. 1/25 to 1/50 of the mass of fuel is injected. As shown in FIG. 12, the fuel F1 injected toward the exhaust pipe side of the concave groove 1 advances in the concave groove 1 toward the exhaust pipe side by the inertia force at the time of injection while evaporating, while the swirl flow S causes the concave groove. 1 and reaches the vicinity of the center of the cylinder. On the other hand, the fuel that has collided with the convex portion 13 is divided into a fuel F21 directed toward the swirl flow upstream and a fuel F22 directed toward the swirl flow downstream because the convex portion has a triangular cross section. The fuel F21 flowing toward the upstream of the swirl flow is conveyed in the circumferential direction of the concave groove 1 by the swirl flow S while evaporating, and reaches near the center of the cylinder. on the other hand,
The fuel F22 flowing toward the downstream side of the swirl flow is carried by the swirl flow S to the intake pipe side of the concave groove 1. As a result, as shown in FIG. 13, the distribution of the fuel vapor becomes a distribution that spreads to the upstream and downstream sides of the swirling flow in the vicinity of the projection 13. The fuel F1 injected toward the exhaust pipe side of the concave groove 1 quickly reaches the vicinity of the ignition plug, so that a mixture with a high fuel concentration is generated in the ignition plug, and the mixture can be reliably ignited. On the other hand, the fuel that has collided with the convex portion 13 is diffused upstream and downstream of the swirling flow, so that it is possible to prevent the mixture having an excessively high vapor concentration from being concentrated near the ignition plug. In the present embodiment, the cross-sectional shape of the projection 13 is triangular. However, the same effect as in the present embodiment can be obtained even if the cross-sectional shape is trapezoidal, pentagonal, or semicircular.

FIG. 14 is a schematic plan view showing a third embodiment of the in-cylinder injection spark ignition engine according to the present invention, and FIG. 15 is a sectional view taken along line AA of FIG. This embodiment is different from the above-described second embodiment in that a flow shielding plate 17 is provided on the exhaust pipe side surface of the projection 13. As shown in FIG.
The flow shielding plate 17 has a function of deflecting the fuel flow from the intake pipe side to the exhaust pipe side in the vicinity of the surface of the projection 13 toward the upstream side and the downstream side of the swirling flow S. As a result, the fuel injected toward the projection 13 can be reliably diffused, and the mixture with an excessively high fuel concentration can be prevented from reaching the vicinity of the ignition plug.

FIG. 16 is a schematic plan view showing a fourth embodiment of the in-cylinder injection spark ignition engine according to the present invention, and FIG. 17 is a sectional view taken along line AA of FIG. In the present embodiment, the convex portion 13 of the second embodiment described above is changed to a concave portion 18. As shown in FIG. 17, the cross-sectional shape of the concave portion 18 is triangular, and the side surfaces 18a and 18b of the concave portion 18
It has a gentle slope with respect to the bottom surface. Also, recess 1
8 is perpendicular to the bottom surface of the groove 1. In this embodiment, similarly to the second embodiment, the swirl flow S is generated in the cylinder at the time of low load and medium load operation, and the exhaust pipe side wall surface 1 of the recess 18 is formed later in the compression stroke.
Fuel is injected from the fuel injection valve 5 so as to straddle 8c.
As shown in FIG. 18, the fuel F1 injected toward the exhaust pipe side of the concave groove 1 quickly reaches the vicinity of the spark plug, thereby generating a fuel-rich mixture in the spark plug,
It is possible to reliably ignite. On the other hand, the fuel colliding with the concave portion 18 collides with the exhaust pipe side wall surface 18c, and is diffused upstream and downstream of the swirling flow. As a result, it is possible to prevent the mixture having an excessively high vapor concentration from being concentrated near the spark plug. In the present embodiment, the cross-sectional shape of the concave portion 18 is triangular, but the same effect as in the present embodiment can be obtained even if it is trapezoidal, pentagonal, semicircular, or the like.

FIG. 20 is a longitudinal sectional view showing a fifth embodiment of the direct injection spark ignition engine according to the present invention, and FIG. 21 is a schematic plan view thereof. In the present embodiment, the bottom surface of the concave groove 1 is formed of a flat surface, and a step 15 is provided on the exhaust pipe side wall surface of the concave groove 1. FIG. 22 shows an enlarged view of the step portion 15. Step 15
Is a surface perpendicular to the bottom surface of the groove 1, and the upper surface of the step portion 15 is a surface parallel to the bottom surface of the groove 1. In the present embodiment, as in the first embodiment described above, the swirl flow S is generated in the cylinder at the time of low-load and medium-load operation, and then, at the latter stage of the compression stroke, almost at the center of the bottom surface of the groove 1. The fuel is injected from the fuel injection valve 5 toward the fuel injection valve. FIG.
As shown in FIG. 1, the fuel F1 injected into the groove 1 is vaporized, moves in the groove 1 toward the exhaust pipe by inertia force at the time of injection, and is swirled by the swirling flow S in the circumferential direction of the groove 1. Carried. Eventually, the fuel collides with the side surface 15b of the step portion 15,
Change the flow direction upward. As shown in FIG. 22, the fuel tends to move further upward due to inertial force even after passing through the edge portion 16 of the step portion 15. However, since the pressure on the exhaust pipe side of the edge portion 16 decreases, the fuel at the edge portion 16 Separation vortices are generated and the steam circulates on the step 15. Thereby, mixing of fuel and air and vaporization of fuel are promoted, and the flow of steam rising toward the spark plug as shown in FIG. 7 is weakened. As a result, it is possible to prevent the mixture having an excessively high fuel vapor concentration from reaching the vicinity of the spark plug.

As shown in FIG. 23, by forming the edge 16 of the step 15 at an acute angle, a circulating flow on the step 15 can be generated more reliably. FIG.
The same effect can be obtained by providing the projection 19 on the bottom surface of the concave groove 1 as shown in FIG.

[0025]

According to the present invention, an air-fuel mixture having an appropriate concentration can be stably supplied to the electrode portion of the spark plug during low-load and medium-load operation, so that the ignition performance can be improved and the smolder of the spark plug can be improved. It is possible to reduce the ease and improve the controllability of the ignition timing.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a direct injection type spark ignition engine showing a first embodiment of the present invention.

FIG. 2 is a schematic plan view of a direct injection type spark ignition engine showing a first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a piston of a direct injection type spark ignition engine showing a first embodiment of the present invention.

FIG. 4 is a diagram showing a state of fuel injection in the first embodiment of the present invention.

FIG. 5 is a view showing a fuel behavior in the first embodiment of the present invention.

FIG. 6 is a view showing a fuel behavior in the first embodiment of the present invention.

FIG. 7 is a diagram showing fuel behavior in a conventional method.

FIG. 8 is a diagram showing a change in a fuel-air ratio around a spark plug according to a conventional method and the present invention.

FIG. 9 is a longitudinal sectional view of a direct injection type spark ignition engine showing a second embodiment of the present invention.

FIG. 10 is a schematic plan view of a direct injection type spark ignition engine showing a second embodiment of the present invention.

FIG. 11 is a sectional view of a piston of a direct injection type spark ignition engine showing a second embodiment of the present invention.

FIG. 12 is a view showing a fuel behavior in a second embodiment of the present invention.

FIG. 13 is a view showing a fuel behavior in a second embodiment of the present invention.

FIG. 14 is a schematic plan view of a direct injection type spark ignition engine showing a third embodiment of the present invention.

FIG. 15 is a sectional view of a piston of a direct injection type spark ignition engine showing a third embodiment of the present invention.

FIG. 16 is a schematic plan view of a direct injection type spark ignition engine showing a fourth embodiment of the present invention.

FIG. 17 is a cross-sectional view of a piston of a direct injection type spark ignition engine showing a fourth embodiment of the present invention.

FIG. 18 is a view showing a fuel behavior in a fourth embodiment of the present invention.

FIG. 19 is a schematic configuration diagram of a direct injection type spark ignition engine according to the first to fifth embodiments of the present invention.

FIG. 20 is a longitudinal sectional view of a direct injection type spark ignition engine showing a fifth embodiment of the present invention.

FIG. 21 is a schematic plan view of a direct injection spark ignition engine showing a fifth embodiment of the present invention.

FIG. 22 is an enlarged view of a cross section of a piston of a direct injection type spark ignition engine showing a fifth embodiment of the present invention.

FIG. 23 is an enlarged view of a cross section of a piston of a direct injection type spark ignition engine showing a fifth embodiment of the present invention.

FIG. 24 is an enlarged view of a cross section of a piston of a direct injection type spark ignition engine showing a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Concave groove, 4 ... Piston, 5 ... Fuel injection valve, 8 ... Ignition plug, 13 ... Convex part, 13a ... Side surface which corresponds to the swirl flow upstream side of the convex part, 13b ... Suction wall surface of convex part, 13c ... Convex Side surface corresponding to the downstream side of the swirling flow of the portion, 15: step portion, 15a: intake pipe side wall surface of the step portion, 16: edge portion of the step portion, 17: flow shielding plate, 18: concave portion, 19: projection portion.

Continued on the front page (72) Inventor Toshiharu Nogi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Ryuhei Kawabe 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] An ignition plug is provided substantially at the center of an upper portion of a cylinder, a fuel injection valve is provided on an intake side of a peripheral portion of an upper portion of the cylinder, and a concave groove is formed on a part of a piston top surface. A part of the side wall surface is located substantially below the spark plug, a part of the intake pipe side wall surface of the concave groove is located substantially below the fuel injection valve, and a swirl flow around the central axis of the cylinder during the intake / compression stroke. In the in-cylinder injection type spark ignition engine configured to be generated, a convex portion is provided on a part of the exhaust pipe side bottom surface of the concave groove, and the intake pipe side wall surface of the convex portion is formed by a vertical wall surface, A side surface corresponding to the swirl flow upstream side and a side surface corresponding to the swirl flow downstream side of the convex portion are formed by a slope having a gentle slope with respect to the concave groove bottom surface, and the upper surface of the convex portion is formed by a flat surface, and at least low load or medium load. In the latter half of the compression stroke during operation, the fuel injection direction of the fuel injection valve extends across the intake pipe side wall surface of the projection. Cylinder injection type spark ignition engine, characterized in that defined. 2. An engine according to claim 1, further comprising: a spark plug substantially at the center of an upper portion of the cylinder, a fuel injection valve on an intake side of an upper peripheral portion of the cylinder, a groove on a part of a piston top surface, and an exhaust pipe of the groove. A part of the side wall surface is located substantially below the spark plug, a part of the intake pipe side wall surface of the concave groove is located substantially below the fuel injection valve, and a swirl flow around the central axis of the cylinder during the intake / compression stroke. In the in-cylinder injection spark ignition engine configured such that a convex portion is provided on the intake pipe side bottom surface of the concave groove, and a side surface corresponding to the swirl flow upstream side and a side surface corresponding to the swirl flow downstream side of the convex portion are provided. The fuel injection system is constituted by a gentle slope with respect to the groove bottom, and at least in the latter stage of the compression stroke at the time of low load or medium load operation, crosses the boundary between the exhaust pipe side wall surface of the protrusion and the groove bottom. An in-cylinder injection spark ignition engine, wherein a fuel injection direction of a valve is determined. 3. The in-cylinder injection spark ignition engine according to claim 2, further comprising means for blocking the flow of air from the intake pipe side near the surface of the projection to the exhaust pipe side. In-cylinder injection spark ignition engine. 4. A cylinder having an ignition plug substantially at the center of an upper part thereof, a fuel injection valve on an intake side of an upper peripheral part of the cylinder, a concave part on a part of a piston top surface, and an exhaust pipe of the concave part. A part of the side wall surface is located substantially below the spark plug, a part of the intake pipe side wall surface of the concave groove is located substantially below the fuel injection valve, and a swirl flow around the central axis of the cylinder during the intake / compression stroke. In the in-cylinder injection type spark ignition engine configured to generate a concave portion, a concave portion is provided on the intake pipe side bottom surface of the concave groove, and a side surface corresponding to the swirl flow upstream side and a side surface corresponding to the swirl flow downstream side of the concave portion are formed in the concave portion. The fuel injection valve is constituted by a gentle slope with respect to the groove bottom surface, and at least in the latter stage of the compression stroke at the time of low load or medium load operation, straddles the boundary between the exhaust pipe side wall surface of the recess and the groove bottom surface. An in-cylinder injection spark ignition engine, characterized in that an injection direction is determined. 5. A cylinder having an ignition plug substantially at the center of an upper part thereof, a fuel injection valve on an intake side of a peripheral part of the upper part of the cylinder, a concave part on a part of a piston top surface, and an exhaust pipe of the concave part. A part of the side wall surface is located substantially below the spark plug, a part of the intake pipe side wall surface of the concave groove is located substantially below the fuel injection valve, and a swirl flow around the central axis of the cylinder during the intake / compression stroke. In the in-cylinder injection spark ignition engine configured to be generated, the injection direction of the fuel injection valve is determined so that the fuel injected from the fuel injection valve in the latter half of the compression stroke is directed to the bottom surface of the groove. The fuel injected from the fuel injection valve at least in the late stage of the compression stroke at the time of low-load or medium-load operation rises toward the spark plug along the groove wall surface and is parallel to the central axis of the cylinder and connected to the spark plug. Circulates around an axis perpendicular to the plane passing through the central axis of the fuel injector, Countercurrent-cylinder injection spark ignition engine, characterized in that it comprises means for generating a flow of the exhaust pipe direction from the intake pipe in the combustion chamber top. 6. The direct injection type spark ignition engine according to claim 5, wherein a step is provided between an exhaust pipe side wall surface of the concave groove and a concave groove bottom surface. Spark ignition engine. 7. The in-cylinder injection spark ignition engine according to claim 6, wherein a junction between the upper surface of the step and the side surface of the concave groove on the intake pipe side is formed by an acute angle edge. In-cylinder injection spark ignition engine.