JPH0914103A - In-cylinder injection engine - Google Patents

Abstract

(57) Abstract: A cylinder injection engine capable of performing stratified mixture combustion and uniform premixed combustion. In a cylinder injection engine 1 having a cylinder injection valve 14 for injecting fuel into a cylinder 6d, two intake valve openings 10a and 10b are formed in a cylinder head 3 in parallel in a cam axis direction, When viewed in the cylinder axis direction, the intake valve openings 10a and 10b are formed at positions where the distance L1 from the line connecting the centers of the intake valve openings to the cylinder axis C is 1/4 or less of the cylinder radius L. The injection port 14b of the fuel injection valve 14 is arranged between the intake valve openings 10a and 10b of the cylinder head 3 as viewed in the cylinder axis direction, and the injection axis is arranged to face the exhaust side.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, there has been proposed an in-cylinder injection engine in which a fuel injection valve is mounted on a cylinder head so as to face a combustion chamber and fuel is directly injected and supplied into a cylinder. The fuel injection valve is configured such that an injection port having a predetermined injection angle can be opened and closed by a valve body that is driven forward and backward by an electromagnetic coil, and the energization time to the electromagnetic coil is controlled according to the required fuel amount. The opening time of the injection port is controlled, and the fuel injection amount is adjusted accordingly.

[0003]

In the in-cylinder injection engine, however, a uniform premixed combustion in which the combustion speed is increased by uniformly diffusing and distributing the fuel in the cylinder in accordance with the operating state of the engine, or It is required to perform a stratified mixture combustion that prevents knocking under a high load by forming a high concentration mixture near the spark plug and forming a lean mixture at a corner of the combustion chamber.

The present invention has been made to meet the above-mentioned conventional demands, and an object of the present invention is to provide a cylinder injection engine capable of performing stratified mixture combustion and uniform premixed mixture combustion.

[0005]

According to a first aspect of the present invention, in a cylinder injection engine having a cylinder injection valve for injecting fuel into a cylinder, two intake valve openings are provided in a cylinder head in a cam axis direction. Formed in parallel, the two intake valve openings are formed at positions where the distance from the line connecting the centers of the two intake valve openings to the cylinder axis is 1/4 or less of the cylinder radius when viewed in the cylinder axis direction, The fuel injection valve is characterized in that the injection port of the fuel injection valve is located between the intake valve openings of the cylinder head as viewed in the cylinder axis direction, and the injection axis extends toward the exhaust side.

According to a second aspect of the present invention, in the first aspect, the intake camshaft is arranged so that at least a part of the intake camshaft is located in a cylinder projection plane when viewed in the cylinder axis direction, and the fuel injection valve is provided. It is characterized in that it is inserted and disposed between the intake port of the cylinder head and the block-side mating surface so as to be substantially parallel to the straight portion of the intake port.

According to a third aspect of the present invention, there is provided an in-cylinder injection engine equipped with an in-cylinder injection valve for injecting fuel into a cylinder,
A cavity that forms a combustion chamber with the combustion concave portion of the cylinder head is provided at the top of the piston so that the fuel injected through the in-cylinder injection valve enters the cavity of the piston that is rising near the top dead center. Is installed in the cavity, reflects the injected fuel on the exhaust side of the peripheral wall surface of the cavity, guides part of the reflected fuel toward the spark plug, and guides the other part into the cavity. It is characterized by forming an inclined surface.

According to a fourth aspect of the present invention, in the third aspect, the cavity is eccentrically arranged on the exhaust side, and an intake inclined surface for introducing air into the cavity is formed on the intake side of the cavity, and the squish on the intake side is formed. The feature is that the surface is formed wider than the squish surface on the exhaust side.

According to a fifth aspect of the invention, in the fourth aspect, the cavity is a three-leaf type as a whole including a portion extending from the center of the cylinder to the introduction inclined surface side and a portion extending to the left and right sides of the reflection inclined surface. It is characterized by

According to a sixth aspect of the present invention, in the fourth aspect, opposed concave portions facing the left and right intake valve openings are provided on the left and right sides of the introduction inclined surface.

A seventh aspect of the present invention is an in-cylinder injection engine having an in-cylinder injection valve for injecting fuel into a cylinder,
Two intake valve openings are formed in parallel on the cylinder head in the cam axis direction, and the injection port of the fuel injection valve is located between the intake valve openings of the cylinder head when viewed in the cylinder axis direction.
In addition, the injection axis is arranged to face the exhaust side, the ignition plug is arranged near the cylinder axis, and the portion of the cylinder head combustion chamber ceiling wall between the both intake valve openings is It is characterized in that a projection portion is formed to prevent the injected fuel of 1. from directly impinging on the electrode of the spark plug and to promote atomization of the injected fuel.

[0012]

According to the in-cylinder injection engine of the first aspect of the invention, the intake valve openings arranged in parallel are largely offset to the cylinder axis side, and the injection port of the fuel injection valve is arranged on both sides of the cylinder head. Since the fuel is injected toward the exhaust side by being positioned between the intake valve openings, intake air is introduced into the cylinder from the vicinity of the center of the cylinder in the axial direction of the cylinder, and the intake side of the cylinder inner peripheral surface is exhausted. Along the part, it flows vertically and a pair of left and right vertical vortices (tumbles) are generated. Then, the fuel is injected toward the exhaust side through the space between the two tumble flows.
Therefore, a stratified air-fuel mixture is formed which has a high-concentration air-fuel mixture in the central portion of the cylinder and a low-concentration air-fuel mixture in the left and right portions.

According to the second aspect of the invention, the intake camshaft is
Since it is arranged so that it intersects with the valve axis of the intake valve when viewed in the cam axis direction and that at least a part of the intake cam shaft is located in the cylinder projection plane when viewed in the cylinder axis direction, the intake port should be installed upright. It is possible to secure a space for disposing the fuel injection valve between the intake port and the block-side mating surface.

According to the third aspect of the invention, the fuel injected from the fuel injection valve collides with the reflective inclined surface of the cavity of the piston, a part of which is blown up to the ignition plug side and ignited around the ignition plug. A possible high-concentration mixture is formed, and the rest forms a high-concentration mixture in the cavity. As a result, a high-concentration air-fuel mixture is formed around the spark plug and the cavity and a low-concentration stratified air-fuel mixture is formed around the cavity.

According to the fourth aspect of the present invention, the cavity is eccentrically arranged on the exhaust side, an introduction inclined surface for introducing air into the cavity is formed on the intake side of the cavity, and the squish surface on the intake side is exhausted. Since it is formed wider than the squish surface on the side, when the piston rises near the top dead center, air flows into the cavity, and the vortex of this most air promotes mixing of the fuel and air guided in the cavity. A uniform mixture can be formed in the cavity.

According to the fifth aspect of the present invention, the cavity is a three-leaf type as a whole, which includes a portion extending from the center of the cylinder to the introduction inclined surface side and a portion extending to the left and right sides of the reflection inclined surface. The air flowing into the cavity more reliably generates the vortex, and the mixing of the fuel and the air is further promoted.

According to the sixth aspect of the present invention, since the opposed concave portions facing the left and right intake valve openings are provided as recesses, the generation of vortices can be increased, the mixing of fuel and air can be further promoted, and the combustion efficiency can be increased. Can be improved.

According to the invention of claim 7, since the protrusion is formed on the inner surface of the top wall of the cylinder head, the fuel injected and supplied is divided into left and right parts by the protrusion. Therefore, it is possible to prevent the injected fuel from directly impinging on the ignition plug, and by providing the protrusion, the temperature particularly near the separated fuel reaching portion becomes high, and atomization of the fuel can be promoted.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The first aspect of the invention of claims 1 to 6 is as follows.
An embodiment will be described with reference to the drawings. In all the drawings of this specification, the same reference numerals indicate the same or corresponding parts.
1 to 13 are views for explaining the in-cylinder injection engine according to the first embodiment, and FIGS. 1 and 2 are sectional side views (sectional views taken along the line II and II-II in FIG. 3). 3, FIG. 3 is a bottom view of the cylinder head, FIG. 4 is a plan view of the piston, FIG. 5 is a cross-sectional side view of the injection nozzle portion of the fuel injection valve, and FIGS.
Is a plan view of the cylinder liner, a sectional side view, FIG. 8 is an injection characteristic diagram of the fuel injection valve, FIGS. 9 and 10 are engine speed-load-operating state characteristic diagrams for explaining the operation, and FIGS. Is a schematic diagram showing a homogeneous premixed combustion and stratified mixture combustion states, and FIG. 13 is a schematic diagram showing a lift curve of an intake valve.

In the figure, reference numeral 1 is a water-cooled 4-cycle parallel multi-cylinder 4-valve engine, in which a cylinder head 3 is connected to a head-side mating surface of a cylinder block 2 by a head bolt 20 and is formed above the cylinder head 3. It has a structure in which the formed cam chamber 4 is covered with a head cover 5.

A piston 7 is provided in the cylinder block 2.
A cast iron cylinder liner 6 having a cylinder bore 6d into which is slidably inserted is fixedly inserted. A flange portion 6a is formed thickly on the upper portion of the cylinder liner 6 and has a height of about 1/2 of a piston stroke. The upper surface of the flange portion 6a communicates with a cooling jacket 3f in the cylinder head 3. An annular groove portion 6b is formed, and the annular groove portion 6b has a through hole 6c formed so as to penetrate the flange portion 6a in an obliquely downward direction.
Of the cooling jacket 2a.

The piston 7 is formed by forming a pin boss portion 7b into which a piston pin is inserted in a cylindrical portion 7a and closing an upper end with a top portion 7c. The top portion 7c is provided with a recess on the lower surface of the cylinder head 3. A cavity 8 that forms a combustion chamber with the formed combustion recess 3a is provided as a recess. As shown in FIGS. 2 and 4, this cavity 8 has a circular recess 8a.
An introducing portion 8b that projects radially outward on the intake side of the circular recess 8a, and a reflecting portion 8c that projects radially outward on the exhaust side of the circular recess 8a.

The center point P of the recess 8a is deviated from the cylinder axis C to the exhaust side by f. Further, the introduction portion 8b is for introducing the injected fuel into the cavity 8, and an introduction inclined surface 8d is formed at the outer end portion thereof. The reflecting portion 8c is for blowing up a part of the fuel injected from the fuel injection valve 14 to the spark plug 9 side and directing the rest toward the inside of the cavity 8, and a reflecting inclined surface 8e is formed inside thereof. Has been done. The reflective inclined surface 8e is located substantially at the center of the cylinder, and the reflective inclined surface 8e
The electrode 9a of the spark plug 9 is located directly above e.

In the combustion recess 3a of the cylinder head 3, two left and right intake valve openings 10a and 10b and two left and right exhaust piece openings 11a and 11b are opened. As shown in FIG. 1, the left and right intake valve openings 10a and 10b are led to a rear wall 3b of the cylinder head while being joined by a bifurcated intake port 12a. Here, the intake port 12a has a throat portion 12b, which is coaxial with the valve shaft 15b of the intake valve 15 and is relatively long when viewed in the cam shaft direction (see FIG. 1).
A space for disposing the fuel injection valve 14, which will be described later, is secured between the straight portion 12c of a and the block-side mating surface 3g.

A branch portion 12d of the intake manifold 12 is connected to the intake port 12a. A bias valve 17 is arranged in the branch portion 12d. The non-uniform flow valve 17 has a cutout portion 17a, and a valve shaft 17b parallel to the cam shaft.
It is rotatable around a fully open position and a closed position shown by a solid line in FIG. 2, and is opened and closed by an actuator (not shown). When the drift valve 17 is rotated to the closed position, intake air is taken in by the top wall of the intake port 12a and the cutout portion 1.
7a and flows toward the top wall side, and flows axially from the cylinder center side along the exhaust side inner surface of the cylinder bore 6d and reverses at the piston top surface. A pair of left and right eddies, so-called tumble, are generated.

Further, the left and right exhaust valve openings 11a, 11
b is led out to the cylinder head front wall 3c while being joined by a bifurcated exhaust port 13a, and an exhaust pipe 13 is connected to the leading opening.

As shown in FIG. 3, the left and right intake valve openings 10a and 10b are located at a distance from the line A passing through the cylinder axis C and parallel to the cam axis to the intake valve openings 10a and 10b. L1 is largely deviated to the exhaust side so as to be ¼ or less of the cylinder bore radius L, and is separated in the cam axis direction to such an extent that a required gap is obtained between the L1 and the screw insertion hole of the ignition plug 9. It is installed in.

Due to the displacement of the intake valve openings 10a and 10b toward the exhaust side, a wide flat squish surface 3d is secured in the combustion recess 3a of the cylinder head 3 between the left and right intake valve openings 10a and 10b. An injection opening 3e is formed at the center of the squish surface 3d in the cam axis direction. In the injection opening 3e, the straight line portion 12c is provided between the straight line portion 12c of the intake port 12a and the block-side mating surface 3g.
The injection portion 1 of the fuel injection valve 14 inserted and arranged substantially parallel to c
4a is located.

The fuel injection valve 14 includes the injection portion 14a.
The injection nozzle 14b formed inside is opened and closed by a valve body 14c that is driven forwards and backwards by an electromagnetic coil. The tip surface 14e of the injection portion 14a is the inner surface of the combustion recess 3a and the squish surface 3d. It is formed to be flush. Further, as shown in FIGS. 2 and 5, when the piston 7 is located at a stroke position of 1/2 to 1/3 from the top dead center, the injection nozzle 14b causes the fuel to flow to the reflection inclined surface 8e of the piston 7. Its angle so that it is jetted toward
The direction is set. In this case, the injection angle is set to θ, and the injection direction is set to an angle θ ′ between the axis of the injection valve 14 and the axis of the injected fuel. Reference numeral 14f is a fuel supply rail that supplies high-pressure fuel to the fuel injection valve 14.

The left and right intake valve openings 10a and 10b are also provided.
Can be opened and closed by the valve heads 15a of the left and right intake valves 15 and 15, and the left and right exhaust valve openings 11a and 11b.
Can be opened and closed by the valve heads 16a of the left and right exhaust valves 16, 16. The intake valve 15 and the exhaust valve 16 are arranged so that their respective valve shafts 15b, 16b form a predetermined sandwiching angle, and the lifters 17, 17 attached to the upper ends of the respective valve shafts 15b, 16b are Opening and closing are driven by intake and exhaust cam shafts 18 and 19, respectively.

The intake camshaft 18 is pivotally supported by a bearing portion 18a and a bearing cap 18b formed on the cylinder head 3 side, and the exhaust camshaft 19 is bearing portion 19a and a bearing cap 19b on the cylinder head 3 side. Is pivotally supported by. The intake cam shaft 18 is arranged at a position higher than the exhaust cam shaft 19 by e.

Here, the exhaust valve 16 is arranged with an inclination angle such that the intersection point b between the axis a of the exhaust valve 16 and the exhaust cam shaft 19 substantially coincides with the extension line c of the most exhaust side of the cylinder bore 6d. . Further, the intake valve 15 has its axis a '.
Is intersected with the intake cam shaft 18 at an inclination angle deviated by d from the extension line c'of the most intake side portion of the cylinder bore 6d toward the cylinder axis. That is, in the engine of the present embodiment, the cam shafts 18 and 19 are arranged with a narrow interval such that the axes thereof are located substantially within the projection plane of the cylinder bore 6d in the cylinder axis direction, and the valve holding angle is about 20. It is as narrow as °.

By setting the valve holding angle to be narrow in this way, the valve heads 15a and 16a have a substantially flat surface, and as a result, the surface shape of the combustion recess 3a becomes substantially flat and the volume of the combustion recess 3a becomes large. Is small, and a high compression ratio is achieved while providing the cavity 8.

Further, since the valve holding angle is made small, the straight portion 12c of the intake port 12a can be erected so that the angle formed with the cylinder axis becomes small, and the throat portion 12b is set to be long, A fuel injection valve 1 is provided between the intake port 12a and the block-side mating surface 3g.
The arrangement space of 4 was secured.

Further, as described above, since the intake camshaft 18 is arranged at the height of the dimension e, the intake port 12a can be erected while ensuring the necessary throat length, and the space for disposing the fuel injection valve 14 can be increased. Was secured.
And because we got a relatively large space for placement,
The cooling jacket 3f can be formed so as to surround the fuel injection valve 14, and the fuel injection valve 14 can be arranged at a position where fuel can be injected toward the combustion chamber 3a.

Here, the engine 1 is provided with an intake valve opening / closing timing variable mechanism for changing the opening / closing timing of the intake valve 15, which is a combination of a valve timing variable mechanism and a valve lift variable mechanism. As described below, only the closing timing of the intake valve can be changed without changing the opening timing of the intake valve.

In the variable valve lift mechanism, a cylinder 17a is formed inside the intake lifter 17, and the cylinder 17a is formed.
A piston member 17b having an escape hole 17c in a is inserted and arranged so as to be movable back and forth in the direction perpendicular to the valve axis.
When the piston member 17a is moved forward, the operation of the lifter 17 is directly transmitted to the intake valve 15 via the piston member 17a, and the lift curve becomes a curve a in FIG. On the other hand, when the piston member 17b is retracted, the escape hole 17c of the member 17b and the valve shaft 15b coincide with each other, the intake valve 15 idles by the depth of the escape hole 17c, and the lift curve is the curve b in FIG. Becomes

The variable valve timing mechanism is a known mechanism for changing the phase angle between the cam shaft 18 and the timing sprocket. When the phase angle is changed while the lift curve is the curve b, the timing curve changes. Change to curve c. As a result, the opening timing of the intake valve is θo.
While the closing timing changes from θc to θc ′.

This intake valve opening / closing timing variable mechanism is provided with the intake valve 15
The opening timing is constant, and the closing timing can be freely changed in the range from before bottom dead center (for example, 60 °) during the piston descending stroke to after bottom dead center (for example, 60 °) during the ascending stroke. There is. When the intake valve 15 is closed at 60 ° before bottom dead center, the substantial compression ratio is 11, and 6 after bottom dead center.
It is 16 when closed at 0 °.

The engine 1 is equipped with an ECU (not shown) for controlling the operation of the engine.
Is a non-uniform flow valve control means for controlling the operation of the actuator for the non-uniform flow valve (tumble valve) 17, as a variable mechanism control means for controlling the operation of the intake valve opening / closing timing variable mechanism, and the injection timing of the fuel injection valve 14, It functions as an injection valve control means for controlling the injection amount and the like.

Next, the function and effect will be described. In this engine 1, as shown in FIG. 9 (a), in the low / medium speed / high load operation range S1, the low compression ratio operation is performed by closing the intake valve 15 before the bottom dead center during the piston descending stroke. In the other operating range S2, the basic compression ratio operation is performed in which the intake valve is closed at the normal timing after bottom dead center during the piston rising stroke.

Further, as shown in FIG. 9 (b), in the medium / high speed / high load operation range S3, a uniform premixed gas operation is performed in which the fuel injection start timing is before bottom dead center during the piston descending stroke, and other than that. In the operation range S4, the stratified mixture operation is performed with the fuel injection timing after the bottom dead center during the piston ascending stroke.

As a result, as shown in FIG. 10, the intake valve early closing operation and the early fuel injection operation are carried out in the medium speed and high load operation range S5, and the most uniform premixed air operation is performed in this operation range S5. Will be done.

In the operating range S5, the uniform premixed combustion is carried out so that the fuel is uniformly diffused in the entire cylinder to increase the combustion speed. For that purpose, the ECU uses the actuator to position the drift valve 17 at the fully open position, and FIG.
As shown in FIG.
The closing timing of 5 is set to before the bottom dead center in the piston descending stroke, for example, 60 °, and the fuel injection valve 14 is operated to start the fuel injection immediately after the intake valve 15 is closed.

Since the non-uniform flow valve 17 is located at the fully open position, the intake air is introduced into the cylinder through the entire intake port 12a, so that the above tumble hardly occurs (see FIG. 11 (a)). On the other hand, since the cavity 8 formed on the top portion 7c of the piston 7 is deviated to the exhaust side and the squish surface 3d having a large area is formed on the intake side, the cavity 7 is increased as the piston 7 moves upward. Swirl occurs within 8 (see FIGS. 1B and 1D).

Due to the early closing of the intake valve 15, the substantial compression ratio becomes 11, and the cylinder pressure decreases until the piston 7 reaches the bottom dead center. Since the fuel is injected and supplied in this depressurized state, the injected fuel is atomized by the depressurization boiling phenomenon, and the spread angle of the spray is increased to substantially increase the injection angle. A uniform air-fuel mixture is created and the burning speed is improved. In this case, the injection characteristic of the fuel injection valve 14 is as shown in FIG.
Since a larger amount of fuel is injected on the injection start side, the fuel is intensively injected in the depressurized state, and from this point as well, the spread angle of the spray increases.

Further, since the temperature of the air-fuel mixture at the start of compression decreases due to the depressurization boiling phenomenon of the fuel, the temperature rise of the air-fuel mixture at the end of the compression stroke is suppressed even in the high load operation range, and knocking can be prevented accordingly. .

In the operation area S6, a combustible high-concentration mixture is formed near the plug and the cavity 8
A stratified mixture is formed in which the fuel is confined in the inside as a homogeneous mixture and the remaining region is a lean mixture. For that purpose, the ECU operates the above-mentioned actuator and operates the above-mentioned drift valve 1
7 to the fully closed position, and the intake valve opening / closing timing variable mechanism is used to set the closing timing of the intake valve 15 to after bottom dead center (for example, 60 °) in the piston descending stroke, and the fuel injection valve 14 is set. As late as possible (eg 120 ° before top dead center)
At, the fuel injection is started. As a result, the substantial compression ratio becomes about 14.

When the bias valve 17 is fully closed, intake air flows unevenly toward the top wall of the intake port 12a, passes through the left and right intake valve openings 10a and 10b near the cylinder axis, and reaches the exhaust side surface of the cylinder bore 6d. A pair of left and right tumble flows are generated in the cylinder bore 6d (see FIG. 12 (a)).

On the other hand, the fuel is injected between the left and right tumble flows toward the reflecting inclined surface 8e of the piston 7 at the 1/2 to 1/3 stroke position with the injection angle θ. Therefore, in the cylinder bore 6d, a stratified air-fuel mixture is formed in which the central portion has a high concentration capable of being sufficiently ignited and the left and right portions are not ignited (FIGS. 12B and 12E).
reference).

From the fuel injection valve 14 to the piston 7
The fuel injected into the cavity 8 of the
And part of it blows up to reach the vicinity of the electrode 9a of the ignition plug 9, and a high-concentration air-fuel mixture that can be ignited is formed near the electrode 9a. Further, the rest of the fuel reflected by the collision goes inward of the cavity 8 (see FIG. 12).
(C) and (f)).

Since the cavity 8 is deviated to the exhaust side, the introduction portion 8b having the introduction inclined surface 8d is provided on the intake side, and the squish surface 3d having a large area is formed on the intake side, the piston 7 is moved upward. , Air flows into the cavity 8 while forming a horizontal vortex (swirl). The vortex of the air promotes mixing with the fuel flowing into the cavity, and a uniform air-fuel mixture is formed in the cavity 8 (see FIGS. 12D and 12G).

In this way, stratified mixture combustion in which a high-concentration mixture is formed around the spark plug and a uniform mixture is formed in the cavity 8 can be realized, and the combustion speed is improved.

In this case, since there is almost no combustible air-fuel mixture in the area outside the spark plug outside the cavity 8, abnormal ignition does not occur at the corner of the combustion chamber even under high load, and the high compression ratio is achieved. It is possible to suppress the occurrence of knocking while maintaining (for example, about 14).

FIG. 14 is a view showing the cavity of the piston according to the second embodiment of the invention of claim 5. The concave portion of the cavity 38 of the present embodiment is provided with the introduction portion 8 from the center of the cylinder.
a portion 38a extending to the side of the introduction inclined surface 8d of b, and the reflecting portion 8
Portions 38b, 38 extending to the left and right of the reflective inclined surface 8e of c
It is a three-leaf type as a whole consisting of b and b.

In the present embodiment, since the concave portion of the cavity 38 is of a three-leaf type, the turbulent intensity of the squish flow flowing into the cavity 38 is increased, the mixing of fuel and air is further promoted, and the combustion speed is increased. To do.

FIGS. 15 to 19 are views showing a cylinder injection engine according to a third embodiment of the invention of claims 6 and 7, and FIG. 15 is a sectional side view of a main part of this engine, and FIG.
Is a bottom view of the cylinder head, FIG. 17 is a plan view showing the cavity of the piston, and FIGS. 18 and 19 are views showing temperature changes in the combustion chamber.

In the figure, reference numeral 40 designates the left and right intake valve openings 10a, 10 which open in the combustion recess 3a of the cylinder head 3.
It shows a protrusion arranged between b (valve bridge). The projection 40 surrounds the separation wall surfaces 40a and 40a for separating the fuel injected and supplied from the injection opening 3e into left and right flows D and E, and the electrode 9a of the spark plug 9, and the fuel is applied to the electrode 9a. And a shielding wall surface 40b for avoiding direct contact with

The cavity 41 of the piston 7 is recessed on the left and right sides of the introduction inclined surface 8d, and has opposed recesses 42a and 42b facing the left and right intake valve openings 10a and 10b.

As described above, in this embodiment, the injected fuel is separated into the left and right flows D and E by the protrusion 40, and the intake valve openings 10a and 10a are provided on the left and right sides of the introduction inclined surface 8d.
Since the facing recesses 42a and 42b facing the 10b are provided, it is possible to further promote the mixing of fuel and air.

Further, since the projection 40 is provided, the injected fuel is separated into the left and right flows D and E, and the injected fuel can be prevented from directly hitting the electrode 9a of the spark plug 9. Further, by providing the protrusion 40, the temperature in the vicinity of the arrival position of the separated fuel is increased and atomization is promoted.

Here, the temperature distribution in the fuel recess 3a of the cylinder head due to the provision of the protrusion 40 was measured. In this measurement, the points 50, 51, 56, 55 on the straight line A where the protrusion 40 is formed and the points 53, 52, 57, 5 on the straight line B connecting the intake valve opening and the exhaust valve opening.
8 was examined.

As shown in FIGS. 18 and 19, at any of the points, the temperature rises as the engine speed and speed increase, but especially the point located between the reaching portions of the left and right directional flows D and E. The temperatures of 56 and 57 increase significantly as the engine speed and speed increase. As a result, sufficient heat is given to the separated fuel, and atomization is promoted.

Generally, in an engine, it is necessary to atomize a large amount of fuel as the engine speed increases,
Moreover, it is necessary to shorten the time required for this atomization. In this engine, the left and right intake valve openings 10 in the combustion recess 3a are
Since the protrusion 40 is provided between a and 10b, the protrusion 4
When 0, the temperature of the fuel reaching portion can be increased, and the fuel evaporation time can be shortened accordingly.

In FIG. 18, F is 800 rpm.
, G is 4800 rpm, H is 5600 rp
It is a characteristic line showing a temperature change of each above-mentioned point in case of m, respectively. In FIG. 19, I is 60 km / h, J is 120 km / h, and K is 180 km / h.
It is a characteristic line which shows the temperature change of each said point at the time of respectively.

[0066]

According to the in-cylinder injection engine of the first aspect of the present invention, the intake valve openings arranged in parallel are largely offset to the cylinder axis side, and the injection port of the fuel injection valve is arranged in the cylinder head. Since the fuel is injected toward the exhaust side by being positioned between the intake valve openings, a pair of left and right vertical vortices (tumble) is generated in the cylinder, and the fuel is the tumble flow. Is injected toward the exhaust side through the space between them, so that a high-concentration air-fuel mixture is formed in the center of the cylinder and
On the right side, a stratified mixture that is a low concentration mixture is formed,
Particularly, there is an effect that the occurrence of knocking can be suppressed during low speed rotation and high load operation.

According to the second aspect of the present invention, since the intake camshaft is arranged so as to be located within the cylinder projection plane in the cylinder axis direction, the intake port can be arranged upright, and the intake port and the block side can be arranged. There is an effect that a space for disposing the fuel injection valve can be secured between the contact surface and the surface.

According to the third aspect of the invention, the piston has a reflective inclined surface for guiding a part of the injected fuel toward the spark plug and the remaining part into the cavity in the cavity of the piston. In addition, a stratified mixture having a high concentration and a low concentration around the cavity can be formed, and knocking can be suppressed.

According to the fourth aspect of the present invention, the cavity is eccentrically arranged on the exhaust side, an introduction inclined surface for introducing air into the cavity is formed on the intake side of the cavity, and the squish surface on the intake side is exhausted. Since it is formed wider than the squish surface on the side, air can be made to flow into the cavity as the piston rises near the top dead center, and the vortex of this air causes the flow of fuel and air guided in the cavity. Mixing is promoted, a uniform air-fuel mixture can be formed in the cavity, and the combustion speed can be improved.

According to the invention of claim 5, the cavity as a whole is composed of a portion extending from the introduction inclined surface to the introduction inclined surface side from the center of the cylinder, and a portion extending to the left and right of the reflection inclined surface. Since it is of the three-leaf type, the air flowing into the cavity more reliably generates a vortex, the mixing of the fuel and the air is further promoted, and the combustion speed can be further improved.

According to the sixth aspect of the present invention, since the opposed concave portions facing the left and right intake valve openings are provided on the introduction inclined surface side,
There is an effect that the mixing of fuel and air is further promoted and the combustion speed can be further improved.

According to the seventh aspect of the present invention, since the protruding portion for cutting and separating the injected fuel is arranged in the valve bridge of the cylinder head, it is possible to prevent the injected fuel from directly impinging on the ignition plug, and also the fog of the fuel. There is an effect that can promote the conversion.

[Brief description of the drawings]

1 is a sectional side view of a direct injection engine according to a first embodiment of the present invention (claims 1 to 4) (a sectional view taken along line II in FIG. 3).

FIG. 2 is a sectional side view of the engine of the first embodiment (FIG. 3).
II-II line sectional view).

FIG. 3 is a bottom view of the cylinder head of the engine of the first embodiment.

FIG. 4 is a plan view of a piston of the engine of the first embodiment.

FIG. 5 is a sectional side view of a fuel injection valve of the engine of the first embodiment.

FIG. 6 is a plan view of a cylinder liner of the engine of the first embodiment.

FIG. 7 is a sectional side view of the cylinder liner of the engine of the first embodiment.

FIG. 8 is an injection characteristic diagram of the fuel injection valve of the engine of the first embodiment.

FIG. 9 is an engine speed-load-operating state characteristic diagram for explaining the operation of the engine of the first embodiment.

FIG. 10 is an engine speed-load-operating state characteristic diagram for explaining the operation of the engine of the first embodiment.

FIG. 11 is a schematic diagram showing a uniform premixed combustion state of the engine of the first embodiment.

FIG. 12 is a schematic diagram showing a stratified mixture combustion state of the engine of the first embodiment.

FIG. 13 is a schematic diagram showing a lift curve of the engine of the first embodiment.

FIG. 14 is a plan view showing a cavity of a piston according to a second embodiment of the invention of claim 5;

FIG. 15 is a sectional side view of an essential part of an engine according to a third embodiment of the present invention.

FIG. 16 is a bottom view of the cylinder head of the engine of the third embodiment.

FIG. 17 is a plan view showing a cavity of a piston of the engine of the third embodiment.

FIG. 18 is a temperature characteristic diagram of the engine of the third embodiment.

FIG. 19 is a temperature characteristic diagram of the engine of the third embodiment.

[Explanation of symbols]

1 in-cylinder injection engine 3 cylinder head 3a combustion recess 3d intake side squish surface 3g block side mating surface 6d cylinder bore (cylinder) 7 piston 7c piston top 8,38 cavity 8d introduction slope 8e reflection slope 9 spark plug 10a, 10b Intake valve opening 12a Intake port 14 Fuel injection valve 14b Injection nozzle (injection port) 15 Intake valve 18 Intake cam shaft 40 Protrusion C Cylinder shaft 42a. 42b Opposed recess c'Intake valve valve axis L Cylinder radius L1 Distance from the line connecting the centers of both intake valve openings to the cylinder axis

Claims (7)

[Claims] 1. An in-cylinder injection engine having an in-cylinder injection valve for injecting fuel into a cylinder, wherein two intake valve openings are formed in a cylinder head in parallel in the cam axis direction and viewed in the cylinder axis direction. The distance from the line connecting the centers of the intake valve openings to the cylinder axis is 1/4 of the cylinder radius.
The fuel injection valve is formed at the following position, and the injection port of the fuel injection valve is arranged between the intake valve openings of the cylinder head as viewed in the cylinder axis direction, and the injection axis is arranged to face the exhaust side. A cylinder injection engine characterized in that 2. The intake camshaft according to claim 1, wherein the intake camshaft is arranged so that at least a part of the intake camshaft is located in a cylinder projection plane when viewed in the cylinder axis direction, and the fuel injection valve is provided in the camshaft direction. The in-cylinder injection engine is characterized in that it is inserted between the intake port of the cylinder head and the mating surface on the block side so as to be substantially parallel to the straight portion of the intake port. 3. An in-cylinder injection engine provided with an in-cylinder injection valve for injecting fuel into a cylinder, wherein a cavity forming a combustion chamber with a combustion recess of a cylinder head is recessed at the top of a piston. The injection fuel is arranged so that the injected fuel enters the cavity of the piston that is rising near the top dead center, and the injected fuel is collided and reflected on the exhaust side of the peripheral wall surface of the cavity, An in-cylinder injection engine characterized in that a reflective inclined surface is formed to guide a part of the reflected fuel toward the spark plug and guide the other part into the cavity. 4. The cavitation according to claim 3, wherein the cavity is eccentrically arranged on the exhaust side, an introduction inclined surface for introducing air into the cavity is formed on the intake side of the cavity, and a squish surface on the intake side is formed on the exhaust side. A cylinder injection engine characterized by being formed wider than the squish surface. 5. The cavity according to claim 4,
An in-cylinder injection engine having a three-leaf type as a whole including a portion extending from the center of the cylinder toward the introduction inclined surface and portions extending to the left and right of the reflection inclined surface. 6. The in-cylinder injection engine according to claim 4, wherein opposed recesses facing the left and right intake valve openings are provided on the left and right sides of the introduction inclined surface. 7. An in-cylinder injection engine having an in-cylinder injection valve for injecting fuel into a cylinder, wherein two intake valve openings are formed in a cylinder head in parallel in the cam axis direction and viewed in the cylinder axis direction. The injection port of the fuel injection valve is located between the both intake valve openings of the cylinder head, the injection axis is arranged toward the exhaust side, and the ignition plug is arranged near the cylinder axis. It is possible to prevent the fuel injected from the fuel injection valve from directly impinging on the electrode of the spark plug at a portion of the top wall of the combustion chamber of the head between the intake valve openings and to promote atomization of the injected fuel. The in-cylinder injection engine is characterized in that a projection portion for forming is formed.