JP3932853B2 - 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 internal combustion engine.
[0002]
[Prior art]
As disclosed in Japanese Patent Application Laid-Open No. 11-303710, a general internal combustion engine fuel injection device includes a valve body that contacts an annular tapered seat portion, a fuel reservoir directly downstream of the seat portion, and a fuel And a nozzle hole communicating with the reservoir. When the fuel is injected, the valve body is separated from the seat portion, whereby high-pressure fuel flows into the fuel reservoir through the seat portion, whereby the fuel is injected from the fuel reservoir through the injection hole.
[0003]
[Problems to be solved by the invention]
If the injection hole is formed on the central axis of the seat portion, the fuel that has flowed into the fuel reservoir easily flows into the injection hole and is injected. However, for example, in the case where the nozzle hole is deviated with respect to the central axis of the seat portion and communicated with the fuel reservoir, a relatively wide space is formed on the side opposite to the nozzle hole in the fuel reservoir, The fuel that has flowed into the fuel reservoir from the non-biased side of the seat portion easily forms a vortex that swirls in the vertical direction in this space. When such a vortex is formed, energy loss of the fuel flowing into the nozzle hole occurs, so that the penetrating force of the injected fuel is reduced or the flow velocity of the fuel passing through the nozzle hole is reduced. It becomes difficult to form a fuel spray having an intended shape due to the occurrence of equilibrium.
[0004]
Accordingly, an object of the present invention is to provide a fuel injection device in which the nozzle hole is deviated from the central axis of the valve body seat portion and communicates with the fuel reservoir, and fuel flowing into the fuel reservoir from the valve body seat portion is contained in the fuel reservoir. In other words, it is possible to form a fuel spray of an intended shape having a strong penetration force without forming a vortex.
[0005]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, comprising: a valve body; an annular tapered seat portion in contact with a seat corner portion of the valve body; and a fuel located immediately downstream of the seat portion. A reservoir, and a single injection hole that is deviated from the central axis of the seat portion and communicates with the fuel reservoir, and the displacement of the injection hole causes a displacement from the displacement side of the injection hole in the fuel reservoir. The space on the counter-bias side becomes large, and a chamfer is formed on at least the counter-bias side between the seat portion and the fuel reservoir, and at the tip end portion of the valve body from the corner portion of the seat. protrusion protruding from the surface constituting the tip portion to the tip portion in the axial direction of the valve body is provided, the fuel passing through the counter-biasing side of the seat portion, said projection of said chamfer and the valve body substantially in the space of the counter-biased side by parts Characterized in that it is guided to part.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic longitudinal sectional view in a cylinder of a cylinder injection type spark ignition internal combustion engine to which a fuel injection device according to the present invention is attached, and FIG. 2 is a plan view of a piston in FIG. In these drawings, reference numeral 1 denotes an intake port that communicates with the inside of the cylinder via an intake valve 3. An exhaust port 2 communicates with the inside of the cylinder via the exhaust valve 4. Reference numeral 5 denotes a piston, and a concave cavity 8 is formed on the top surface.
[0008]
6 is an ignition plug disposed substantially at the center of the upper part of the cylinder, and 7 is a fuel injection device for directly injecting fuel from the periphery of the upper part of the cylinder into the cylinder, that is, a fuel injection valve. The fuel injection valve 7 is disposed on the intake port side where the temperature becomes relatively low due to the intake air flow in the cylinder in order to prevent fuel vapor.
[0009]
Moreover, the fuel injection valve 7 has a slit-shaped injection hole, and injects fuel in the substantially fan shape with thin thickness. In order to perform stratified combustion, as shown in FIG. 1, fuel is injected into a cavity 8 formed on the top surface of the piston 5 in the latter half of the compression stroke. Although the fuel immediately after the injection indicated by the oblique lines is in a liquid state, it spreads in the width direction and is likely to be vaporized in order to make sufficient contact with the high-pressure and high-temperature intake air in the cylinder when flying in the cylinder. As it advances along the width 8a and spreads in the width direction, it absorbs heat from a wide area of the bottom wall 8a, and is easily vaporized. The fuel being vaporized in this way is deflected upward by the opposing side wall 8b.
[0010]
As shown in FIG. 2, the opposing side wall 8b has an arc shape in plan view. As a result, the fuel that has progressed and vaporized on the bottom wall 8a of the cavity 8 gathers in the center due to the arc shape of the opposing side wall 8b, and becomes a lump of combustible air-fuel mixture indicated by dots in the vicinity of the spark plug 6. Thus, stratified combustion can be realized as lean combustion by igniting and burning this combustible mixture. Thus, since the fuel spray is guided to the vicinity of the spark plug by its own inertial force, a relatively strong penetration force is required to form a good combustible mixture. A strong penetration force is also preferable for increasing the frictional force with the intake air during flight and vaporizing the fuel.
[0011]
This in-cylinder injection type spark ignition internal combustion engine forms not only such stratified combustion but also fuel in the intake stroke to form a homogeneous mixture in the cylinder at the time of ignition, and this homogeneous mixture is ignited and combusted. Homogeneous combustion is also possible. Unlike the stratified combustion in which the fuel injection period is limited to the latter half of the compression stroke, such homogeneous combustion is mainly performed at high rotation and high load because a large amount of fuel can be injected. During homogeneous combustion, the relatively thin, generally fan-shaped fuel spray spreads in the width direction during flight in the cylinder, and there is a portion that is difficult to come into contact with the intake air in the cylinder, such as the central part of the conical fuel spray. In addition, since the entire spray is sufficiently in contact with the intake air, it is easy to vaporize, which is advantageous for forming a good homogeneous mixture. In addition, if the penetration force of the fuel spray is strong, the frictional force with the intake air becomes larger as in the stratified combustion, so that the fuel is more easily vaporized.
[0012]
FIG. 3 is a cross-sectional view of the tip portion of the fuel injection valve 7. An annular tapered seat surface 72 with which the valve body 71 abuts is formed at the tip of the fuel injection valve 7, and a cap-shaped fuel reservoir 73 is formed downstream of the seat surface 72. . The cap shape of the fuel reservoir 73 is composed of a cylindrical shape in contact with the seat surface 72 and a hemispherical shape having the same radius as this cylindrical shape. A slit-like injection hole 74 communicating with the fuel reservoir 73 is further formed at the tip of the fuel injection valve 7.
[0013]
4 is a cross-sectional view taken along the line AA in FIG. 3. As shown in FIGS. 3 and 4, the nozzle hole 74 has two thicknesses that are separated from each other in the thickness direction of the substantially fan-shaped fuel spray and are substantially parallel to each other. It has a width direction wall and two width direction walls spaced apart with a predetermined depression angle B in the width direction of the fuel spray. The center line in the thickness direction of the two walls in the width direction indicated by the alternate long and short dash line intersects with the hemispherical center C of the fuel reservoir 73. The center line in the thickness direction may slightly deviate from the hemispherical center C and intersect the center axis of the sheet surface.
[0014]
As shown in FIG. 1, the fuel injection valve 7 is attached at a relatively small angle with respect to the boundary surface between the cylinder head and the cylinder block because of the attachment space. However, if the fuel is injected in the axial direction of the fuel injection valve 7 attached in this way, it is difficult to inject the fuel into the cavity 8 on the top surface of the piston 5, so as shown in FIG. The fuel is injected at a predetermined angle D with respect to the direction. Therefore, the two thickness direction walls of the injection hole 74 are formed to be inclined at a predetermined angle D with respect to the axis of the fuel injection valve 7.
[0015]
As shown in FIGS. 3 and 4, when the valve body 71 is lifted and the seat corner 71a of the valve body 71 is separated from the seat surface 72, the high-pressure fuel stored in the pressure accumulating chamber (not shown) or the like is The fuel flows into the fuel reservoir 73 through 72, and the fuel is injected from the fuel reservoir 73 through the injection hole 74. If the fuel thus injected becomes a substantially fan-shaped spray along the shape of the nozzle hole 74 and has a relatively strong penetration force, as described above, during the stratified combustion, it can be vaporized easily and reliably. In this way, a good combustible air-fuel mixture can be formed. Further, during homogeneous combustion, it can be easily vaporized to form a good homogeneous mixture.
[0016]
FIG. 5 is a cross-sectional view of the tip of a general fuel injection valve 7 ′. The same reference numerals are assigned to the same components as those in FIG. The annular tapered seat surface 72 comes into contact with the seat corner portion 71a ′ of the valve body 71 ′ to stop high-pressure fuel in order to stop fuel injection. In order to complete this seal, it is necessary to provide a sufficient resistance against the pressing force acting in the axial direction of the valve body 71 ′. For this purpose, the seat surface 72 is placed on the axis E. It must be tilted at a relatively large angle F. Similarly, in the fuel injection valve 7 of the present embodiment, the seat surface 72 is inclined at a relatively large angle with respect to the axis E.
[0017]
As described above, the nozzle hole 74 is inclined at the predetermined angle D with respect to the axis E. As a result, the injection hole 74 is in communication with the fuel reservoir 73 while being offset with respect to the axis E, that is, with respect to the central axis of the seat portion 72. Thus, when the fuel reservoir 73 is considered at the opening of the nozzle hole 74, the space 73a on the counter-bias side is larger than the space 73b on the side of the nozzle hole, and the space 73a on the counter-bias side is relatively small. It will be wide.
[0018]
During fuel injection, the fuel flows into the fuel reservoir 73 through the seat portion 72. However, since the seat portion 72 is inclined at a relatively large angle F with respect to the axis E as described above, As indicated by arrows in FIG. 5, the fuel that flows into the fuel reservoir 73 from the nozzle hole deflection side of the seat portion 72 flows into the upper portion (valve element side) of the deflection side space 73 b of the fuel reservoir 73, and also the seat portion 72. The fuel flowing into the fuel reservoir 73 from the nozzle hole opposite side of the nozzle hole flows into the upper part of the counter-bias side space 73a, and then these two fuel flows collide with each other and pass through the vertical plane (the hole hole 74). It progresses downward (injection hole side) of the fuel reservoir 73 along the vicinity (perpendicular to the center plane in the width direction).
[0019]
At this time, since the bias side space 73b of the fuel reservoir 73 is narrow, the fuel flow does not swirl, but the anti-bias side space 73a is wide and the fuel passes through its surroundings. As indicated by arrows in FIG. 5, the fuel tends to form a vortex swirling in the vertical direction. When such a vortex is formed, energy loss of the fuel flowing into the nozzle hole occurs, so that the penetrating force of the injected fuel is reduced or the flow velocity of the fuel passing through the nozzle hole is reduced. It becomes difficult to form a fuel spray having an intended shape due to the occurrence of equilibrium.
[0020]
In the fuel injection valve 7 of this embodiment, as shown in FIG. 3, a tapered chamfer 75 is formed between the seat portion 72 and the fuel reservoir 73. As a result, as shown by an arrow in FIG. 3, the fuel that flows into the fuel reservoir 73 from the nozzle hole deflection side of the seat portion 72 is guided by the chamfer 75 to the substantially central portion of the bias side space of the fuel reservoir 73. The fuel flowing into the fuel reservoir 73 from the nozzle hole counter-bias side of the seat portion 72 is guided to the substantially central part of the counter-bias side space.
[0021]
Thus, in this embodiment as well, the anti-bias side space of the fuel reservoir 73 is wide, but the fuel flow guided to the substantially central portion does not form a vortex in the anti-bias side space and flows into the nozzle hole 74. Because there is no energy loss of the fuel to be injected, the penetration force of the injected fuel does not decrease, and there is no imbalance in the flow velocity of the fuel passing through the nozzle hole Thus, it is possible to form a fuel spray having an intended shape.
[0022]
Further, in the present embodiment, the tip of the valve body 71 facilitates the introduction of the fuel flowing into the fuel reservoir 73 from the nozzle hole deflection side of the seat portion 72 to the substantially central portion of the deflection side space, and The fuel that flows into the fuel reservoir 73 from the nozzle hole counter-bias side protrudes by a protrusion 71b that facilitates the introduction of the fuel into the substantially central portion of the counter-bias side space.
[0023]
As a result, the fuel flowing into the fuel reservoir 73 from the nozzle hole counter-bias side of the seat portion 72 is more reliably guided to the substantially central portion of the counter-bias side space, and it is ensured that a vortex is generated in the fuel reservoir 73. Can be prevented.
[0024]
In the present embodiment, the chamfer 75 is formed on the entire circumference between the seat portion 72 and the fuel reservoir 73. As a result, the fuel flowing into the fuel reservoir 73 from the nozzle hole counter-bias side of the seat portion 72 is guided to the substantially central portion of the anti-bias side space, and in addition to the inside of the fuel reservoir 73 from the nozzle hole bias side of the seat portion 72. The fuel that flows in is guided to a substantially central portion of the bias side space. As described above, since the bias side space of the fuel reservoir is narrow, it is difficult for the fuel vortex to be formed even if the fuel is not led to substantially the center. Thereby, the chamfer 75 may be formed only on the counter-bias side between the seat portion 72 and the fuel reservoir 73. However, by using this embodiment, the generation of vortices can be completely prevented even in the bias side space of the fuel reservoir 73. The same applies to the protrusion 71b of the valve body 71.
[0025]
In the present embodiment, the nozzle hole 74 is a slit nozzle hole for forming a substantially fan-shaped fuel spray. This does not limit the invention. For example, even when the nozzle hole having a round cross section is formed at the same position as the slit nozzle hole, the anti-bias side space of the fuel reservoir 73 is similarly widened, and if a vortex is formed here, the nozzle hole An energy loss of the fuel flowing into the fuel occurs, and the penetration force of the injected fuel is also reduced. Accordingly, even in this case, it is effective to provide the chamfer 75 and the protruding portion 71b as in the present embodiment. Finally, in the present embodiment, the annular tapered shape of the seat portion 72 is actually a truncated cone shape, but may be any annular tapered shape such as a truncated pyramid shape.
[0026]
【The invention's effect】
According to the fuel injection device for an internal combustion engine according to the present invention, when the space on the counter-bias side is larger than the space on the bias side of the nozzle hole in the fuel reservoir due to the bias of the nozzle hole, the space between the seat portion and the fuel reservoir is increased. A chamfer is formed at least on the anti-bias side, and a protruding portion that protrudes in the axial direction of the valve body from the surface that forms the distal end portion is provided at the distal end portion from the corner portion of the seat of the valve body. The fuel passing through the anti-bias side of the seat portion is guided to the substantially central portion of the space on the anti-bias side by chamfering and the protruding portion of the valve body. As a result, the generation of vortices can be prevented in a large anti-bias side space where vortices are easily formed, and the energy loss of fuel in the fuel reservoir is suppressed. It can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal cross-sectional view of a cylinder injection type spark ignition internal combustion engine equipped with a fuel injection device according to the present invention.
2 is a top view of a piston of the direct injection spark ignition internal combustion engine of FIG. 1. FIG.
FIG. 3 is a sectional view of a tip portion showing an embodiment of a fuel injection valve.
4 is a cross-sectional view taken along the line AA in FIG. 3;
FIG. 5 is a cross-sectional view of a tip portion of a general fuel injection valve.
[Explanation of symbols]
6 ... Spark plug 7 ... Fuel injection valve 71 ... Valve body 71b ... Projection 72 ... Seat surface 73 ... Fuel reservoir 74 ... Injection hole 75 ... Chamfer

Claims (1)

A valve body, an annular taper-shaped seat portion with which a seat corner of the valve body abuts, a fuel reservoir located immediately downstream of the seat portion, and a fuel reservoir deviated from a central axis of the seat portion A single injection hole communicating therewith, and due to the deviation of the injection hole, a space on the counter-bias side in the fuel reservoir becomes larger than a space on the deflection side of the injection hole, and the seat portion and the fuel reservoir, A chamfer is formed at least on the anti-bias side between the valve body, the tip side portion of the valve body from the sheet corner portion, and the axis of the valve body from the surface constituting the tip side portion at the most distal portion A projecting portion projecting in the direction is provided, and fuel passing through the anti-biasing side of the seat portion is guided to a substantially central portion of the space on the anti-biasing side by the chamfering and the projecting portion of the valve body. A fuel injection device for an internal combustion engine.

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