JP3832584B2 - Fuel injection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for an in-cylinder injection spark ignition internal combustion engine (hereinafter simply referred to as an engine) that directly injects fuel into the cylinder.
[0002]
[Related background]
In an in-cylinder injection type engine in which fuel is directly injected into a cylinder, since the fuel spray shape greatly affects the combustion state in the cylinder, various proposals have been made to form an appropriate fuel spray. For example, there is a fuel injection valve that uses a swirl injector that diffuses fuel spray in a conical shape (for example, Patent Documents 1 and 2).
[0003]
In the techniques described in these patent documents, a deep dish cavity is formed on the top surface of the piston, and the intake port is formed substantially upright, and the intake air flowing from the intake port in the compression stroke is inverted upward by the cavity, The fuel spray from the swirl injector is transferred to the vicinity of the spark plug using the reverse tumble flow generated by this, and an ignitable air-fuel mixture is formed around the spark plug, and then the stratified fuel is diluted around the periphery. Combustion is possible.
[0004]
However, since the fuel spray is reversed on the piston cavity by using the intake air flow, the fuel tends to adhere to the piston top surface and accumulate, and the local over-riching causes a decrease in thermal efficiency, HC, soot, smoke, etc. In the following, there is a problem of increasing the emission). In addition, since the fuel spray of the swirl injector has a weak penetration force, the spray characteristics change according to the in-cylinder pressure and the in-cylinder temperature, and the fuel transfer using the intake air flow is affected by carbon deposition in the combustion chamber. Therefore, there has been a problem that stable fuel transfer is hindered and it is difficult to realize reliable stratified combustion.
[0005]
Therefore, a technique has been proposed in which fuel is transferred using the momentum of the fuel and the cavity shape of the piston without depending on the intake air flow (see, for example, Patent Document 3). In Patent Document 3, fuel is injected in two directions from a fuel injection valve, and after the spray has advanced on the cavity bottom wall of the piston, it is deflected upward by both sides of the opposing side wall and led to the vicinity of the spark plug. It is configured.
[0006]
[Patent Document 1]
Japanese Patent No. 3087309
[Patent Document 2]
Japanese Patent Laid-Open No. 10-288039
[Patent Document 3]
Japanese Patent Laid-Open No. 2000-282872
[0007]
[Problems to be solved by the invention]
As is well known, in a fuel injection apparatus that performs this type of stratified combustion, normal ignition cannot be expected unless an appropriate air-fuel mixture is formed around the spark plug at the ignition timing. However, in the technique of Patent Document 3 described above, since the fuel spray deflected by the opposed side wall of the cavity reaches the vicinity of the spark plug and forms a combustible mixture, the combustible mixture is removed at an appropriate timing. In order to form, it was necessary to precisely control the fuel injection timing.
[0008]
The purpose of the present invention is to prevent a decrease in thermal efficiency and an increase in emissions due to fuel adhesion to the piston top surface, and to ensure stratified combustion without being affected by in-cylinder pressure, in-cylinder temperature, carbon deposition, etc. In addition, an object of the present invention is to provide a fuel injection device for an internal combustion engine that can form a combustible air-fuel mixture around a spark plug for a long period of time and can increase the degree of freedom of control during stratified combustion.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is characterized in that a spark plug is disposed substantially at the center of the combustion chamber of the internal combustion engine, and at a predetermined angle with respect to the axis of the spark plug on one side of the intake side of the combustion chamber In a fuel injection device for an internal combustion engine that performs stratified combustion by injecting fuel directly from the fuel injection valve into the combustion chamber during the compression stroke, It is formed around a flat portion near the intake side, and includes a pair of guide walls that extend from both sides of the fuel spray to the vicinity of the lower part of the spark plug, and merges, and the fuel injection valve is convex on the spark plug side, A fuel spray having a concave cross section is formed on the piston side, and the convex side of the fuel spray is directed toward the vicinity of the spark plug and the concave side of the fuel spray is injected toward the vicinity of both guide walls.
[0010]
Therefore, in the compression stroke of the internal combustion engine, the fuel spray is injected from the fuel injection valve so as to intersect the axis of the spark plug at a predetermined angle, the cross-sectional shape of the fuel spray is convex toward the spark plug, and the piston Since it has a concave shape on the side, it can be mixed well in contact with the intake air with a large area. And the convex side of the fuel spray is directed toward the vicinity of the spark plug, and the concave side of the fuel spray is injected toward the vicinity of both guide walls, and the concave side of the fuel spray is then respectively near the lower part of the spark plug along the guide wall. And is joined to the vicinity of the spark plug as the piston rises.
[0011]
Since the fuel is transferred using the momentum of the fuel spray as described above, the fuel spray is less susceptible to the influence of the cylinder pressure, the cylinder temperature, the carbon deposition, etc. as compared with the fuel transfer using the intake air flow. Becomes difficult to adhere in the flat part of the piston.
During fuel injection, the fine particles on the convex side of the fuel spray are taken into the inertial flow of the surrounding air and transported to the spark plug, and the concave side of the fuel spray is the piston guide wall with respect to the convex side of the fuel spray. As a result, the gas is transferred with a time lag as a result, and as a result, a combustible mixture is formed around the spark plug over a long period of time. Therefore, a combustible air-fuel mixture exists around the spark plug in a wide range of piston positions (in other words, ignition timing), and the degree of freedom of control related to the fuel injection timing and ignition timing is expanded.
[0012]
According to a second aspect of the present invention, in the first aspect, the nozzle hole of the fuel injection valve is formed to have an inverted V shape or an inverted U shape.
Therefore, the fuel spray is injected so as to have an inverted V-shaped or inverted U-shaped cross-section corresponding to the injection hole of the fuel injection valve, and the fine particles on the convex side of the fuel spray are directly transported to the spark plug. The concave side of the fuel spray is injected in the vicinity of both guide walls, and is transferred with a time difference with respect to the convex side of the fuel spray.
[0013]
According to a third aspect of the present invention, in the first aspect, the attachment angle or the fuel spray angle of the fuel injection valve is set so that the upper end of the main flow of the fuel spray is directed to the vicinity below the spark plug.
Therefore, the upper end of the main flow of the fuel spray is directed near the lower portion of the spark plug, so that collision of the fuel spray with the spark plug is prevented and momentum is applied to the surrounding air flow induced by the dynamic pressure of the injected spray main flow. A fuel spray roll-up phenomenon in which the lost fuel fine particles are taken in occurs, and the fuel spray fine particles rolled up from the mainstream are transferred to the spark plug. Then, the fuel spray passing through the guide wall with a time difference from the formation of the combustible mixture by the fuel spray is transferred to the ignition plug to form the combustible mixture, and the formation of the combustible mixture over a long period is realized.
[0014]
According to a fourth aspect of the present invention, in the first aspect, the guide wall is formed by raising the periphery of the flat portion, and the height of the raised portion is such that the height of the guide wall is highest on the combustion chamber center side. Is set.
Therefore, the fuel on the concave side injected during the compression stroke is blocked by the guide wall, and the fuel spray being transferred along the guide wall gradually diffuses to increase the volume. In accordance with this, the height of the guide wall is the highest on the combustion chamber center side where the ignition plug is located, so that a situation where fuel spray spills from the flat portion is prevented, and the fuel spray is reliably transferred by the guide wall. .
[0015]
According to a fifth aspect of the present invention, in the first aspect, the guide wall guides the concave side of the fuel spray along the side wall surface of the guide wall facing the fuel injection valve.
Therefore, by guiding the fuel spray on the concave side along the guide wall, the contact area between the fuel spray and the flat portion can be reduced, and the amount of fuel adhering to the flat portion can be reduced as much as possible.
[0016]
Preferably, the lower surface of the cylinder head and the top surface of the piston forming the combustion chamber are each formed as a pent roof type having inclined surfaces inclined to the intake side and the exhaust side. In this case, the raised portion is composed of both pent roof type inclined surfaces and an upper surface.
With this configuration, the lower surface of the pent roof type cylinder head and the top surface of the piston approach each other as the piston rises, and a squish flow toward the center of the combustion chamber is generated. The situation where the fuel spray diffuses from the vicinity of the spark plug is suppressed, and the situation where the fuel spray transferred along the guide wall flows out to the exhaust side is suppressed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an engine fuel injection device embodying the present invention will be described. The engine of this embodiment is configured as an in-line four-cylinder gasoline engine having four valves per cylinder. FIG. 1 is a cross-sectional view showing the configuration of a head portion in a specific cylinder of the engine, and FIG. 2 is a side cross-sectional view as seen from an arrow A in FIG. Side sections are represented in relation to each other. Hereinafter, the configuration of the head portion of the specific cylinder will be described with reference to the same drawing, but the other cylinders have the same configuration.
[0018]
Pistons 2 are slidably inserted into the cylinder 1 a of the cylinder block 1, and a combustion chamber 4 is formed in the cylinder 1 a and between the top surface of the piston 2 and the lower surface of the cylinder head 3. .
A spark plug 5 is disposed in the cylinder head 3 so as to face substantially the center in the combustion chamber 4. A pair of intake ports 6 (only one is shown) is shown on the left side of the figure with the spark plug 5 as the center. One end side is opened, and one end of a pair of exhaust ports 7 (only one is shown) is opened on the right side in the figure. Each intake port 6 is provided with an intake valve 6a, and each exhaust port 7 is provided with an exhaust valve 7a. These intake / exhaust valves 6a, 7a correspond to the rotation of the crankshaft by a camshaft (not shown). Open and close ports 6 and 7.
[0019]
The intake port 6 and the exhaust port 7 have the same shape as a general engine. Although not shown, the other end of the intake port 6 is opened on one side of the cylinder head 3 and is provided with a throttle valve or the like. The other end side of the exhaust port 7 opens to the other side of the cylinder head 3 and communicates with an exhaust passage provided with a catalyst and a silencer. The intake air from the intake passage is adjusted in flow rate by a throttle valve and then flows into the combustion chamber 4 from the intake port 6 when the intake valve 6a is opened. On the other hand, the exhaust gas after combustion in the combustion chamber 4 is discharged from the exhaust valve 7a. As the valve is opened, it is guided from the exhaust port 7 to the exhaust passage and discharged to the outside through the catalyst and the silencer.
[0020]
Between the two intake ports 6 of the cylinder head 3, a fuel injection valve 8 is provided so as to be positioned on the outer peripheral side of the combustion chamber 4, and the fuel injection valve 8 has a posture in which the tip side is inclined slightly downward from the horizontal. The tip is held and directed toward the spark plug 5. As a result, the fuel spray F is injected from the fuel injection valve 8 at a predetermined angle with respect to the axis L of the spark plug 5 in a side view and is directed toward the axis L of the spark plug 5 in a plan view. .
[0021]
3 is a plan sectional view corresponding to the upper stage of FIG. 1 showing the nozzle structure of the fuel injection valve 8, FIG. 4 is a view taken along the arrow B in FIG. 3 showing the nozzle structure, and FIG. FIG. A nozzle hole 8a having a slit shape is formed at the tip of the fuel injection valve 8 (so-called single slit type), and the nozzle hole 8a has an inverted V shape as shown in FIG. With this nozzle structure, a flat fuel spray F in which the cross-sectional shape in the direction orthogonal to the injection direction forms an inverted V shape is injected from both the nozzle holes 8a.
[0022]
Further, although the fuel spray F after the injection gradually diffuses, as shown in the upper part of FIG. 1, as shown in the lower part of FIG. 1, the diffusion angle ψ of the fuel spray F is in the range of 50 to 80 °. Similarly, the ridge line angle θ1 of the lower end of the fuel spray F with respect to the horizontal (for example, the lower surface of the cylinder head 3) is in the range of 30 to 45 °, and the ridge line angle of the upper end of the fuel spray F with reference to the horizontal. The mounting angle of the fuel injection valve 8 and the shape of the injection hole 8a are set so that θ2 is in the range of 20 to -15 ° (in the negative case, it means that the fuel spray F diffuses upward from the horizontal). Has been.
[0023]
Here, the ridge line angle θ1 is set as a value capable of supplying the fuel spray F to the piston top surface, and the main flow (described later) of the fuel spray F at a predetermined fuel injection timing (in other words, the piston position). The fuel spray F excluding the fuel spray Fa generated by the rolling phenomenon) is set to be supplied into the flat portion 10 of the piston 2 described later. Further, the lower ridge line angle θ2 is set so that the upper end of the fuel spray F (corresponding to a convex side having an inverted V-shaped cross section) reaches the spark plug 5.
[0024]
The difference between the ridge line angles (θ1−θ2) is the vertical diffusion angle θ0 of the fuel spray F (the ridge line angles θ1, θ2 and the diffusion angle θ0 are collectively referred to as the fuel spray angle). As a result of setting the ridge line angles θ1, θ2, the width is set narrower than that of, for example, a swirl injector used in a general in-cylinder injection type engine. The optimum ridge line angle θ1 varies depending on the mounting angle of the fuel injection valve 8, the fuel injection timing, and the like. Similarly, the optimum ridge line angle θ2 depends on the positional relationship between the fuel injection valve 8 and the spark plug 5 and the like. Different. Therefore, the ridge line angles θ1 and θ2 are not necessarily limited to the above range, and can be arbitrarily set according to the engine specifications.
[0025]
The fuel pressure supplied to the fuel injection valve 8 is set higher than the fuel pressure (about 5-8 MPa) applied to the swirl injector or the like, for example, 12-14 MPa.
On the other hand, the top surface of the piston 2 is a pent roof type in which inclined surfaces 2b that are inclined to the intake side and the exhaust side are formed with the uppermost flat surface 2a interposed therebetween, and combustion is performed so as to correspond to the top surface of the piston 2 The lower surface of the cylinder head 3 constituting the chamber 4 is also a pent roof type.
[0026]
A flat portion 10 is formed at a position near the intake side (intake port) of the top surface of the piston 2, and the periphery of the flat portion 10 is formed by a flat surface 2 a protruding from the top surface of the piston 2 and an intake / exhaust inclined surface 2 b (lifted portion). It is configured as a guide wall. Although the guide wall is continuous along the peripheral edge of the flat portion 10, as described later, since the fuel transfer action is individually performed on both sides of the fuel injection valve 8, a pair of the guide walls is sandwiched between the fuel injection valves 8 for convenience of explanation. Are divided into guide walls 11a and 11b. Therefore, the respective guide walls 11 a and 11 b are extended from both sides of the fuel injection valve 8 to the exhaust side, and merge in the vicinity below the spark plug 5.
[0027]
Since the flat portion 10 is formed horizontally and the top surface of the piston 2 is a pent roof type, the flat portion 10 has a substantially circular shape opened to the intake side in plan view as shown in the upper part of FIG. 1, the height of the guide walls 11a and 11b is higher on the exhaust side than on the intake side (fuel injection valve side) in the side view, and is highest on the center side of the combustion chamber.
[0028]
6 is a cross-sectional view taken along the line VI-VI in FIG. 1 showing the cross-sectional shape of the guide walls 11a and 11b. The cross-sections of the guide walls 11a and 11b are formed in a circular shape with a predetermined radius r, and the radius r is the guide wall 11a. , 11b, the guide walls 11a, 11b have a reentrant cross-sectional shape that narrows upward.
The engine configured as described above is comprehensively controlled by an ECU (electronic control unit) (not shown). Regarding the fuel injection control, the compression stroke injection in which the fuel injection is performed in the compression stroke and the intake stroke injection in the intake stroke are selectively executed in accordance with the operation region (for example, the engine speed Ne and the engine load).
[0029]
For example, in a region where the engine rotational speed Ne and the engine load are relatively low, switching to compression stroke injection is performed, and stratified combustion is performed in which the fuel spray F is transferred to the vicinity of the spark plug, while the engine rotational speed Ne and the engine load increase. By switching to intake stroke injection, uniform combustion is performed to uniformly mix fuel spray and intake air. In the compression stroke injection, the fuel spray is transferred to the vicinity of the spark plug along two paths. Hereinafter, the fuel spray transfer state in the compression stroke injection will be described.
[0030]
FIG. 7 is a view showing the fuel spray F during injection, FIG. 8 is a view showing the fuel spray F after injection, and FIG. 9 is a view showing the fuel spray F just before ignition. Is a flat cross section and the lower section is a side cross section. 10 is a side sectional view as seen from the arrow C in FIG. 7, FIG. 11 is a side sectional view as seen from the arrow D in FIG. 8, and FIG. 12 is a side sectional view as seen from the arrow E in FIG. is there. FIG. 13 is a partially enlarged view showing the rising of the fuel spray F, which corresponds to the transition from FIG. 7 to FIG. 8 over time.
[0031]
When the piston 2 rises during the compression stroke, fuel is injected from the fuel injection valve 8 at a predetermined crank angle, as shown in FIGS. Since the injected fuel spray F has an inverted V-shaped cross section, the fuel spray F is in contact with the intake air with a large area and is mixed well, and collision with the spark plug 5 is prevented based on the ridge angle θ2.
Here, the collision with the spark plug 5 is prevented by the main flow of the fuel spray F. As shown in FIG. 13, at the time of this fuel injection, the fuel main flow injected as the piston 5 rises. Due to the dynamic pressure, an air flow in the vicinity of the main flow is induced by inertia, and the fuel spray F is rolled up in which the fuel fine particles whose momentum has been lost are successively taken into the air flow, and the fuel spray that has rolled up from the main flow. The fine particles Fa are transferred to the spark plug 5. If the main stream of the fuel spray F that has not been sufficiently atomized collides directly with the spark plug 5, there is a possibility that the fuel will become overconcentrated and the fuel will adhere to the spark plug 5 in the liquid phase and cause the spark plug 5 to be swollen. Since the fuel spray fine particles Fa that have been mainly rolled up in this way are transferred to the spark plug 5, an air-fuel mixture suitable for ignition (combustible air-fuel mixture) is formed around the spark plug 5.
[0032]
On the other hand, as shown in FIGS. 8 and 11, based on the setting of the ridge line angle θ 1 and the diffusion angle ψ, the main flow of the fuel spray F is from the lower end (corresponding to the concave side having an inverted V-shaped cross section) The fuel spray F supplied to the vicinity of the guide walls 11a and 11b is transferred to the vicinity of the lower part of the spark plug 5 along the guide walls 11a and 11b according to its own momentum, and merges. The movement of the fuel spray F is caused by the fact that the spray momentum in the traveling direction is set to a strong point and a high fuel pressure as compared with the swirl injector that converts the fuel pressure into the movement of the swirl direction component.
[0033]
The fuel spray F being transferred along the guide walls 11a and 11b gradually diffuses and increases in volume, and also doubles in volume at the time of merging, but as the volume of the fuel spray F increases, the guide walls 11a and 11b Since the height is increased, the situation in which the fuel spray F spills out from the flat portion 10 is prevented, and the fuel spray F is reliably transferred by the guide walls 11a and 11b.
[0034]
When the piston 2 approaches the compression top dead center and immediately before the ignition timing, as shown in FIGS. 9 and 12, the fuel spray F is pushed up to the vicinity of the spark plug by the rising piston 2 and around the spark plug 5. Forms a combustible mixture. At this point, the lower surface of the pent roof type cylinder head 3 and the top surface of the piston 2 approach each other, and a squish flow S toward the center of the combustion chamber 4 indicated by the arrow is generated. The situation where the fuel spray F diffuses from the vicinity of the spark plug is suppressed.
[0035]
Further, the squish flow S also has an effect of preventing the situation where the fuel spray F after joining flows out from the flat portion 10 to the exhaust side. That is, it is desirable that the momentum of the fuel spray F be completely lost with the merging, but actually, the momentum in the injection direction may remain and flow out from the flat portion 10 to the exhaust side. The spray F is difficult to transfer to the vicinity of the spark plug. Since the squish flow S is generated from the exhaust side as described above, the outflow of the fuel spray F to the exhaust side is suppressed, and as a result, the fuel spray F is reliably transferred near the spark plug.
[0036]
A combustible air-fuel mixture is formed around the spark plug 5 by the fuel spray F and the fuel spray fine particles Fa that have been transferred as described above, and the periphery thereof is kept lean. Therefore, the air-fuel mixture is ignited by the subsequent ignition of the spark plug 5, and stratified combustion is realized.
And, in this embodiment, since the fuel is transferred using the momentum of the fuel spray F, compared to the case where the fuel is transferred using the intake air flow as in the techniques of Patent Documents 1 and 2, for example, It is difficult to be affected by in-cylinder pressure, in-cylinder temperature, carbon deposition, or the like, and stratified combustion can be reliably realized by stable fuel transfer. Further, since the spraying momentum in the traveling direction is set to a strong point and a high fuel pressure as compared with the swirl injector that converts the fuel pressure into the movement of the swirl direction component, the fuel spray F having the momentum is the flat portion 10 of the piston 2. In addition, since it is a part of the entire fuel spray that is not easily collected in the flat portion 10, even if the fuel spray adheres and accumulates in the flat portion 10, the amount of the fuel spray is very small. It is possible to prevent enrichment and prevent a decrease in thermal efficiency and an increase in emissions.
[0037]
Further, as described above, the fuel spray F and the rolled up fuel spray particulates Fa are transferred to the vicinity of the spark plug by following two paths. First, the fuel spray Fa rolled up from the main stream is directly transferred to the spark plug 5; Thereafter, the main flow of the fuel spray F is transferred to the spark plug 5 with a time difference through the guide walls 11a and 11b on the piston top surface. In addition, as with the fuel spray fine particles Fa that are transferred in advance, the fuel spray F that is transferred with a delay after passing through the guide walls 11as and 11b loses its momentum due to merging. Stay long. Therefore, a combustible air-fuel mixture is formed around the spark plug 5 over a long period of time, and the combustible air-fuel mixture exists around the spark plug 5 in a wide range of piston positions (in other words, ignition timing). In addition, the degree of freedom of control regarding the fuel injection timing and the ignition timing can be greatly expanded.
[0038]
On the other hand, this embodiment does not require an upright intake port for generating a reverse tumble flow unlike the techniques of Patent Documents 1 and 2. The technologies of Patent Documents 1 and 2 have problems such as production equipment dedicated to an upright intake port, restrictions on car design due to the overall height of the engine, and cost increase due to a complicated swirl injector. Since the layout can be designed freely, there are no restrictions on production equipment and car design, and there is an advantage that cost reduction can be achieved by adopting a simple fuel injection valve 8 in which the shape of the injection hole is simply changed.
[0039]
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the fuel injection device of a four-valve in-line four-cylinder gasoline engine is embodied. However, the valve mechanism of the engine is changed to an intake / exhaust two-valve, or the cylinder arrangement of the engine is changed. May be.
Moreover, in the said embodiment, although the flat part 10 was formed in the substantially circular shape and the periphery was made into the reentrant-shaped guide walls 11a and 11b, if the fuel spray F can be transferred to the downward vicinity of the spark plug 5, The shapes of the flat portion 10 and the guide walls 11a and 11b are not limited to this. Therefore, for example, a cavity is formed in a substantially heart shape with the tip directed toward the intake side, and its peripheral edge is used as a guide wall, or as shown in FIG. 14, a guide wall 12 having an upright sectional shape is formed. May be.
[0040]
Further, in the above embodiment, the top surface of the piston is a pent roof type, so that the height of the guide walls 11a and 11b is set higher on the exhaust side than on the intake side, that is, highest on the combustion chamber center side. However, instead of this, the top surface of the piston is formed flat, and the bottom surface of the flat portion 10 is inclined so that the center side of the piston 2 is deepened. Also good.
[0041]
In the above embodiment, the lower ridge angle θ2 is set so as to prevent the main flow of the fuel spray F from colliding with the spark plug 5. There is no problem even if spray collision occurs. Therefore, the lower ridge line angle θ2 may be set so that a part of the main flow of the fuel spray F is directly transferred to the spark plug 5.
[0042]
On the other hand, in the above embodiment, the fuel injection valve 8 is formed with the inverted V-shaped injection hole 8a having a slit shape, and the corresponding fuel spray F having a cross-sectional shape is injected, but the shape of the injection hole 8a is the same. It is not limited and can be variously changed. For example, an inverted U-shaped injection hole 31 may be formed as shown in FIG. 15, or a substantially C-shaped injection hole 32 (so-called multi-slit type) may be formed as shown in FIG.
[0043]
Further, as shown in FIG. 17, an inverted V-shaped injection hole 33 may be provided, and in this case, the fuel spray F injected from the provided injection hole 33 merges while colliding. Therefore, a flatter fuel spray is formed, and mixing with intake air can be further promoted as the contact area increases.
Further, as shown in FIGS. 18 and 19, it may be formed as an injection hole group 34, 35 consisting of a plurality of injection holes 34a, 35a (so-called multi-hole type). 16 has the same function as the slit-shaped nozzle hole 8a of FIG. 4, and the nozzle group 17 of FIG. 17 has the same function as the slit-shaped nozzle hole 33 of FIG. Since the diameter of each nozzle hole 34a, 35a is reduced as compared with these slit-shaped nozzle holes 8a, 33, the fuel spray F can be atomized to further promote mixing with the intake air.
[0044]
【The invention's effect】
As described above, according to the fuel injection device of the internal combustion engine of the first and second aspects of the present invention, it is possible to prevent a decrease in thermal efficiency and an increase in emission due to fuel adhesion to the piston top surface, Stratified combustion can be reliably realized without being affected by in-cylinder temperature or carbon deposition, and a combustible air-fuel mixture is formed around the spark plug for a long period of time, increasing the degree of control freedom during stratified combustion. can do.
[0045]
According to a fuel injection device for an internal combustion engine of a third aspect of the present invention, in addition to the first aspect, the spark plug is prevented from rolling when the main flow of fuel spray collides, thereby realizing more reliable stratified combustion. can do.
According to the fuel injection device for the internal combustion engine of the fourth aspect of the invention, in addition to the first aspect, it is possible to prevent the fuel spray from spilling from the guide wall and realize more reliable stratified combustion.
[0046]
According to the fuel injection device for the internal combustion engine of the fifth aspect of the invention, in addition to the first aspect, by reducing the fuel adhesion to the flat portion as much as possible, it is possible to suppress the decrease in thermal efficiency and improve the exhaust emission. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a head portion of an engine according to a first embodiment.
2 is a side cross-sectional view of the configuration of the head portion as seen from the direction of arrow A in FIG.
3 is a cross-sectional plan view corresponding to the upper stage of FIG. 1 showing the nozzle structure of the fuel injection valve.
4 is a view taken along arrow B in FIG. 3 showing the nozzle structure. FIG.
FIG. 5 is a view showing a cross-sectional shape of fuel spray viewed from the direction of arrow B in FIG. 3;
6 is a cross-sectional view taken along the line VI-VI in FIG. 1 showing a cross-sectional shape of the guide wall.
FIG. 7 is a diagram showing fuel spray during injection.
FIG. 8 is a diagram showing fuel spray after injection.
FIG. 9 is a view showing fuel spray just before ignition.
10 is a side sectional view as seen from the direction of arrow C in FIG.
11 is a side sectional view as seen from the direction of arrow D in FIG. 8. FIG.
12 is a side sectional view as seen from the direction of arrow E in FIG. 9;
FIG. 13 is a partially enlarged view showing the fuel spray rolling up.
FIG. 14 is a cross-sectional view showing another example in which the guide wall is formed as a vertical wall.
FIG. 15 is a view showing another example in which the nozzle hole is formed in an inverted U shape.
FIG. 16 is a view showing another example in which the nozzle holes are formed in a substantially C shape.
FIG. 17 is a view showing another example in which an inverted V-shaped injection hole is provided.
FIG. 18 is a view showing another example in which nozzle holes are formed as nozzle hole groups.
FIG. 19 is a view showing another example in which the nozzle holes are formed as a nozzle hole group.
[Explanation of symbols]
2 piston
4 Combustion chamber
5 Spark plug
8 Fuel injection valve
10 Flat part
11a, 11b, 12 guide walls
F, Fa Fuel spray
8a, 31-33, 34a, 35a nozzle hole

Claims (5)

A fuel injection valve having a spark plug disposed at substantially the center of the combustion chamber of the internal combustion engine and a fuel spray that intersects the axis of the spark plug at a predetermined angle on one side of the intake side of the combustion chamber In a fuel injection device for an internal combustion engine that performs stratified combustion by directly injecting fuel into the combustion chamber from the fuel injection valve in the compression stroke,
A pair of guide walls that are formed around a flat portion near the intake side of the piston top surface, extend from both sides of the fuel spray to the vicinity of the lower part of the spark plug, and merge.
The fuel injection valve forms a fuel spray having a convex shape on the spark plug side and a concave shape on the piston side, with the convex side of the fuel spray directed toward the vicinity of the spark plug, and the fuel spray A fuel injection device for an internal combustion engine, wherein the concave side is injected toward the vicinity of both guide walls. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the injection hole of the fuel injection valve is formed in an inverted V shape or an inverted U shape. 2. The fuel injection of the internal combustion engine according to claim 1, wherein the fuel injection valve is set at an attachment angle or a fuel spray angle so that an upper end of a main flow of the fuel spray is directed to a lower vicinity of the spark plug. apparatus. The guide wall is formed by raising the periphery of the flat portion, and the height of the raised portion is set so that the height of the guide wall is highest on the combustion chamber center side. The fuel injection device for an internal combustion engine according to claim 1. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the guide wall guides the concave side of the fuel spray along a side wall surface of the guide wall facing the fuel injection valve.

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