JP4205016B2 - Fuel injection mechanism for in-cylinder direct injection engine - Google Patents

Description

  The present invention relates to a fuel injection mechanism for an in-cylinder direct injection engine that promotes air supply to a fuel jet of fuel in the in-cylinder direct injection engine.

  In the prior art, a venturi-shaped cap portion supported by a nozzle holder portion is provided in the vicinity of the nozzle nozzle hole to recapture the fuel group in the process of injection diffusion from the nozzle and form a mixed jet with air. In the process of allowing the injected fuel group to flow through the base portion, the fuel jet can be activated by mixing the fuel and air and transferring heat to the fuel. The fuel jet exiting the nozzle hole reaches the venturi-shaped inlet entrance while expanding and entraining part of the air in the combustion chamber, and the inlet inlet collides with the guide wall in a straight line and forcibly reassembles inside the nozzle. It will be. In the constricted portion of the mouthpiece, the rigidity energy of each jet is converted into velocity energy from pressure, and a single jet having activated in a uniform density distribution form is formed. It has also been proposed that a single fuel jet formed in this way further collides with a collision diffusion part (see, for example, Patent Document 1).

JP-A-8-4629 (paragraphs 0014-0019, FIGS. 1-3)

  In such a conventional fuel injection mechanism, since most of the injected fluid collides with the wall surface of the venturi-shaped base portion, vaporization of fuel is promoted, but kinetic energy is reduced. For this reason, in the injection in the compression process in which the in-cylinder space, which is often performed in the in-cylinder direct injection engine, becomes a high pressure, there is a problem that the injected fluid does not spread sufficiently in the cylinder. In addition, a part of the non-vaporized jet fluid adheres to the wall surface of the collided venturi-shaped base part, which may cause generation of unburned gas and carbon deposits on the wall surface that affect jet characteristics. was there. This problem was more severe with the collision diffusion part.

  An object of the present invention is to provide a fuel injection mechanism for a direct injection engine in a cylinder that can sufficiently supply air to a fuel jet without causing the fuel jet to collide with a structure to promote mixing of the fuel and air and evaporation of the fuel. Is to provide

In order to solve the above problems, according to the fuel injection mechanism for a direct injection engine of the present invention, the fuel injection mechanism is provided in the vicinity of the injection port of the fuel injection valve facing the combustion space of the direct injection engine, and is injected from the injection port. A duct having an inner peripheral surface that closely surrounds and separates the side surface of the fuel jet, and the air in the upstream space with respect to the fuel jet duct is attracted into the duct by the flow of the fuel jet and mixed with the fuel jet is, between the duct and the upstream space, that have passages for communicating the upstream space is provided only a duct partially circumferential duct.

  A fuel injection mechanism for a direct injection engine according to the present invention includes a duct having an inner peripheral surface that closely surrounds and separates a side surface of a fuel jet injected from an injection port, and a space upstream of the fuel jet duct. The air is attracted into the duct by the flow of the fuel jet and mixed with the fuel jet, so that the effect of promoting air mixing into the fuel jet and evaporation of the fuel can be obtained.

Embodiment 1 FIG.
1 and 2 show a fuel injection mechanism of an in-cylinder direct injection engine according to Embodiment 1 of the present invention. FIG. 1 is a schematic sectional view showing only a portion of the fuel injection mechanism of the in-cylinder direct injection engine. is there. FIG. 2 is an enlarged plan view showing a nozzle hole of the fuel injection mechanism of the direct injection engine shown in FIG.

  The fuel injection mechanism of a direct injection engine in a cylinder according to the present invention is used together with a direct injection engine having a combustion space 2 partially defined by a cylinder head 1. The fuel injection valve 3 is attached to the top wall of the cylinder head 1, and its injection port 4 faces the combustion space 2 and can inject fuel into the combustion space 2 to form a fuel jet 5. In the illustrated example, the nozzle holes 4 have six small nozzle holes 17 as shown in FIG. 2, and the small nozzle holes 17 are arranged in a circle at equal intervals so as to contact a circumscribed circle 7 having a center 6. ing. When the nozzle hole 4 is composed of a plurality of small nozzle holes 17, the center of the group of the small nozzle holes 17 is aligned with the center 6 and arranged to be aligned.

  The fuel injected from the nozzle holes 4 in such a group is injected in the direction determined by the small nozzles 17 from the respective small nozzles 17, and the fuel injected from the other small nozzles 17 and the surroundings When mixed with air, the spray pattern gradually spreads from the group of nozzles 4 as shown as a fuel jet 5 in FIG. 1 as a whole. The outer peripheral surface 8 of the fuel jet 5 having such a spray pattern has a substantially conical shape as a whole from the time when it is injected from the nozzle 4 until the speed is lost, regardless of whether the nozzle 4 is single or plural.

  A flat disk-like partition wall 9 is fixed to the top wall of the cylinder head 1 of the engine by welding or the like over the entire outer periphery. The partition wall 9 directly receives the heat of the combustion flame, but this heat is radiated to the outside through the cylinder head 1. The partition wall 9 is provided in the axial direction of the fuel injection valve 3 by a relatively small predetermined distance A from the fuel injection valve 3.

  In the center of the partition wall 9, a duct 10, which is a circular opening that is axially aligned with the center 6 of the nozzle 4 of the fuel injection valve 3, is provided. A fuel jet 5 from the nozzle 4 passes through the duct 10 and enters the combustion space 2. It is supposed to be supplied. The duct 10 is an edge portion of the opening of the partition wall 9 and is an annular portion having an inner peripheral surface that surrounds the outer peripheral surface 8 of the fuel jet 5 injected from the injection nozzle 4 in a close proximity.

  The disk-shaped partition wall 9 substantially divides the inside of the cylinder except for the duct 10, and forms a combustion space 2 below the partition wall 9 and a space 11 surrounded by the top wall above the partition wall 9. Forming. This space 11 is the upstream space 11 because it is on the upstream side of the duct 10 when viewed in the direction of the flow of the fuel jet 5, and the duct 10 is supported by the partition wall 9 with respect to the cylinder head 1. Therefore, the partition wall 9 supports the duct 10 and substantially partitions the upstream space 11 from the combustion space 2.

  The duct 10 is a cylindrical or annular member having an inlet 12 on the side of the nozzle 4, an inner peripheral surface 13, and an outlet 14, and is an edge portion of the opening of the partition wall 9 in the illustrated example. The partition wall 9 is provided at a predetermined distance A from the fuel injection valve 3, and the partition wall 9 is provided with a duct 10 that is a circular opening. Is provided on the entire circumference of the duct 10 to the upstream space 11. The diameter of the duct 10 is larger than the diameter of the circumscribed circle 7 of the group of the nozzle holes 4, and the inner peripheral surface 13 is close to the side surface of the fuel jet 5, that is, the outer peripheral surface 8, as shown in FIG. Enclosed so as not to touch away. In this way, when the fuel jet 5 passes through the duct 10, the air in the upstream space 11 is drawn in by the flow of the fuel jet 5 and is drawn into the duct 10.

  1 and 2, until the fuel jet 5 is injected from the nozzle 4 of the fuel injection valve 3, the upstream space 11 formed by the partition wall 9 and the combustion space 2 are completely separated by a duct 10 having a circular opening. Both pressures are the same. From this state, when the fuel jet 5 is injected from the nozzle 4 and the fuel jet 5 passes through the duct 10 and flows into the combustion space 2, the air present in the duct 10 is pushed out into the combustion space 2. That is, velocity energy is given to the air existing in the duct 10.

  In the case of a continuous fluid, the sum of pressure energy, velocity energy, and potential energy is always constant in any part of the fluid according to Bernoulli's theorem. If the potential energy is almost the same in any part of the fluid, the velocity energy is given by the injection and pushed out from the duct 10 into the combustion space 2, and the air in the upstream space 11 having little velocity energy is the same as the velocity. Only the air pushed out of the duct 10 into the combustion space 2 has a small pressure energy with the air originally having no energy in the combustion space 2. That is, the pressure of the air pushed out from the duct 10 into the combustion space 2 is lower than the air existing in the upstream space 11 defined by the partition wall 9 and the air in the combustion space 2.

  As a result, ambient air flows toward the duct 10, but in the structure of the fuel injection mechanism of the present invention, the fuel jet 5 is injected while being diffused toward the combustion space 2. 9 flows into the inlet portion 12 of the duct 10 from the upstream space 11 formed by the passage 9 through the flow path 15 between the fuel injection valve 3 and the partition wall 9.

  When air flows into the duct 10 from the upstream space 11, it passes through a flow path 15 that is a gap formed by the fuel injection valve 3 and the partition wall 9. By adjusting the size (distance A) of this gap, etc. By adjusting the size of the flow path 15 to cause the fuel jet 5 to appropriately collide with the air, or to supply air near the fuel jet 5, the air can be entrained in the fuel jet 5. In this way, self-supply of air to the fuel jet 5 is established by the energy of the fuel jet 5.

  As described above, according to the fuel injection mechanism of the direct injection engine of the present invention, the entrainment and evaporation of the liquid components of the fuel jet 5 are promoted by the entrainment of air into the fuel jet 5 and the collision of the air. Thus, an air-fuel mixture in which the fuel jet 5 and air are appropriately mixed can be obtained in a short time.

  The duct 10 has a diameter larger than the diameter of the circumscribed circle 7 of the nozzle 4, and the inner peripheral surface 13 is close to the outer peripheral surface 8 of the fuel jet 5, but surrounds the fuel jet 5. It is made not to touch. Therefore, the fuel jet 5 injected from the fuel injection valve 3 does not collide with the partition wall 9, and the speed of the fuel jet 5, the change in the flow direction, and the fuel adhesion do not occur. Further, the flow path 15 from the upstream space 11 to the duct 10 is opened over the entire circumference of the duct 10, and the air flow into the duct 10 is substantially uniform over the entire circumference. In this way, the influence on the entire or local deformation or direction change of the fuel jet 5 is avoided, and the effects of mixing air into the fuel jet 5 and promoting fuel evaporation are obtained.

Embodiment 2. FIG.
In the fuel injection mechanism of the direct injection engine shown in FIG. 3, the front edge of the duct 10 on the fuel injection valve 3 side, that is, the surface of the lip portion of the inlet portion 12 is rounded, and air is separated therefrom. Has a radius of curvature large enough to prevent Further, the inner peripheral surface 13 of the duct 10 is extended from the one shown in FIG. 1 to be a substantially conical surface, and extends substantially along a part of the outer peripheral surface 8 of the pattern of the fuel jet 5. 8 is close but spaced apart. Other configurations are the same as those described above.

  Since the lip portion of the inlet portion 12 is rounded and formed in this way, air can smoothly flow into the duct 10 from the upstream space 11, resistance is reduced, and a large amount of air is efficiently supplied. can do. Further, since the duct 10 is tapered along the fuel jet 5, the resistance acting on the fuel jet 5 is reduced, so that the influence on the characteristics such as the deformation of the pattern of the fuel jet 5 and the change in the traveling direction is exerted. Can be suppressed.

Embodiment 3 FIG.
In the fuel injection mechanism of the direct injection engine shown in FIG. 4, a circumferential portion of the duct 10 is provided between the duct 10 and the upstream space 11 in order to allow the duct 10 to communicate with the upstream space 11. A plurality of flow paths 16 that are open only are provided. Such a flow path 16 rises from the edge of the circular opening of the partition wall 9 that is the duct 10, extends toward the fuel injection valve 3, is in contact with the fuel injection valve 3, and is disposed so as to form a substantially annular shape as a whole. A plurality of cylindrical partial walls 18 are formed. Further, the nozzle 4 of the fuel injection valve 3 includes a plurality of small nozzles 17 similar to those shown in FIG. 2, but the plurality of flow paths 16 are connected to the small nozzles 17 with respect to the fuel injection valve 3. It is in a position substantially facing in the radial direction. Other configurations are the same as those described above. The cylindrical partial wall 18 may be provided not on the partition wall 9 side but on the fuel injection valve 3 side.

  In FIG. 4, the fuel injection valve 3 is called a multi-hole injector having a plurality of small orifices 17, for example, and the motive power for supplying air to the fuel jet 5 is such that the air guided to the fuel jet 5 flows at high speed. This is the difference in pressure from the ambient air. Therefore, a pressure difference is generated in the vicinity of each fuel jet 5 divided for each small nozzle 17.

  When the flow path 16 to the duct 10 is provided in accordance with the position where the pressure difference occurs, that is, the position of the small nozzle 17, the air flows from the upstream space 11 formed by the partition wall 9 to the small collar 17 as indicated by the broken arrow. To be supplied more smoothly. Further, when the air passes through the flow path 16, the flow path is throttled, so that the air flow rate is increased. As a result, the air strongly collides with the fuel jet 5 and penetrates deeply into the fuel jet 5, and also promotes the fragmentation and evaporation of the fuel molecules in the fuel jet 5. The mechanism by which the air in the upstream space 11 formed by the partition wall 9 is supplied to the fuel jet 5 by the flow action of the fuel jet 5 passing through the duct 10 is the same as that described in relation to the first embodiment. is there.

  Here, the fuel injection valve 3 called a multi-hole injector, for example, having a plurality of small orifices 17 has been described as an example. However, even if the injection port 4 is single, the fuel injection valve in which the injection ports 4 are arranged in a biased manner. The same effect can be provided for a fuel injection valve whose cross-sectional shape is not approximately circular.

Embodiment 4 FIG.
In the fuel injection mechanism of the direct injection engine shown in FIG. 5, a cylindrical partial wall 19 similar to the cylindrical partial wall 18 forming the flow path 16 of FIG. 4 is provided, and a plurality of flow paths 20 are provided. Is formed. These flow paths 20 are provided not at the small nozzle holes 17 but at positions substantially facing the radial direction of the fuel injection valve 3 with respect to the space between the small nozzle holes 17 and 17. Air is supplied from the upstream space 11 toward the space between the small nozzle holes 17. Other configurations are the same as those described above.

  In FIG. 5, the operation of supplying the air in the upstream space 11 formed by the partition wall 9 to the fuel jet 5 by the action of the fuel jet 5 as shown by the broken line arrow is the same as that in the first or third embodiment. However, in this configuration, since the high-speed air flowing from the upstream space 11 formed by the partition wall 9 toward the nozzle 4 does not directly collide with the fuel jet 5, the pattern shape of the fuel jet 5 The effect of mixing air into the fuel jet 5 and promoting fuel evaporation can be obtained without changing the direction.

Embodiment 5 FIG.
In the in-cylinder direct injection engine fuel injection mechanism of the present invention shown in FIG. 6, the partition wall 9 is provided with an intake port 21, which is another opening, at a position away from the duct 10. The combustion space 2 is communicated with the upstream space 11 formed so that air can be supplied from the combustion space 2 to the upstream space 11 through the intake port 21. Other configurations are the same as those described above.

  In FIG. 6, the operation of supplying the air in the upstream space 11 to the fuel jet 5 in the duct 10 through the flow path 15 by the flow action of the fuel jet 5 is the same as that of the first embodiment described above. . When a flow of air occurs due to a pressure difference between the vicinity of the fuel jet 5 and the upstream space 11, the air in the upstream space 11 is discharged and the pressure gradually decreases, and the pressure difference with respect to the vicinity of the fuel jet 5 is increased. Try to get smaller. However, in this embodiment, since the inlet 21 which is another opening is provided at a position away from the duct 10 of the partition wall 9, the pressure of the combustion space 2 and the upstream space 11 formed by the partition wall 9 The pressure can always be kept equal. As a result, the air pressure in the upstream space 11 does not decrease, and the air supply amount does not decrease. Further, since the volume of the upstream space 11 can be suppressed to be equal to or less than the amount of air necessary for fuel injection in one stroke of the engine, air mixing into the fuel jet 5 and acceleration of fuel evaporation can be achieved without reducing the compression ratio of the engine. The effect is obtained.

  Such an air inlet 21 may be a single one as shown in FIG. 6, or a plurality of such inlets 21 may be provided at equal distances or symmetrically with respect to the central shape of the circular partition wall 9, Various shapes and dimensions of the air inlet 21 can be used.

Embodiment 6 FIG.
In the fuel injection mechanism of the direct injection engine shown in FIG. 7, a substantially cup-shaped partition wall 22 that supports the duct 10 and divides the upstream space 11 attaches the fuel injection valve 3 to the cylinder head 1. The support member 23 is fixed by welding or the like. The support member 23 is a substantially cylindrical member that houses and holds the fuel injection valve 3 therein, and is firmly supported by the cylinder head 1 on the outer peripheral surface thereof. The partition wall 22 includes a disc portion 24 that supports the duct 10 that is a circular opening over the entire circumference, and a cylindrical portion 25 that rises in the axial direction from the outer peripheral edge of the disc portion 24. The fuel injection valve support member 23 is fixed at 25. An upstream space 26 is formed between the partition wall 22 and the support member 23 on the upstream side of the duct 10 as viewed in the flow direction of the fuel jet 5. Other configurations are the same as those described above.

  In FIG. 7, the operation of supplying the air in the upstream space 26 formed by the partition wall 22 to the fuel jet 5 by the flow action of the fuel jet 5 is the same as described above. When the fuel injection valve support member 23 is detachable from the cylinder head 1, the positional relationship among the fuel injection valve 3, the injection port 4, and the duct 10 is accurately set and assembled, and then the assembly is assembled. It can be mounted on the cylinder head 1 and the assembly becomes accurate and easy. For example, it can be combined with the various embodiments described so far.

  The partition wall 22 directly receives the heat of the combustion flame. Since the partition wall 22 is thermally joined to the fuel injection valve support member 23, this heat is cooled by the engine cooling via the fuel injection valve support member 23 and the cylinder head 1. Cooled by water (not shown).

Embodiment 7 FIG.
In the fuel injection mechanism of the direct injection engine shown in FIG. 8, the partition wall 27 that supports the duct 10 is directly fixed to the fuel injection valve 3 by welding or the like. One end of the partition wall 27 is fixed to the outer peripheral portion of the front end portion of the fuel injection valve 3, and the other end is supported by the duct 10, which is an annular portion protruding slightly radially inward from the partition wall 27. . The duct 10 surrounds the outer periphery of the fuel jet 5 injected from the nozzle 4 of the fuel injection valve 3 in a close proximity but is spaced apart. Thus, the cylindrical partition wall 27 partitions the upstream space 28 upstream of the duct 10 from the combustion space 2 when viewed in the direction of the flow of the fuel jet 5. As long as the duct 10 is formed at the edge of the partition wall 27, there may be no portion protruding radially inward.

  In such a fuel injection mechanism of a direct injection engine, the operation in which the air in the upstream space 28 is supplied to the fuel jet 5 passing through the duct 10 is the same as that described so far. The positional relationship among the injection valve 3, the injection port 4, and the duct 10 can be accurately set and mounted on the cylinder head 1 after assembling, and the assembling becomes accurate and easy.

  In the various embodiments and modifications described so far, the air is sufficiently supplied to the fuel jet without colliding the fuel jet against the structure to promote the mixing of the fuel and the air and the evaporation of the fuel. The present invention provides a fuel injection mechanism for an in-cylinder direct injection engine, but the same effects can be obtained by variously combining these embodiments and modifications.

It is a schematic sectional drawing which shows the fuel-injection mechanism of the cylinder direct injection engine which is Embodiment 1 of this invention. It is an enlarged plan view which shows the relationship between the nozzle of the fuel injection valve of the fuel injection mechanism of the direct injection engine of FIG. 1, and a partition. It is a schematic sectional drawing which shows the fuel-injection mechanism of another in-cylinder direct injection engine which is Embodiment 2 of this invention. It is a perspective view which fractures | ruptures and shows the structure of the air flow path provided in the partition which is Embodiment 3 of this invention. It is a perspective view which fractures | ruptures and shows another structure of another air flow path provided in the partition which is Embodiment 4 of this invention. It is a schematic sectional drawing which shows the example which provided the air inlet in the partition which is Embodiment 5 of this invention. It is a schematic sectional drawing which shows the example which attached the partition which is Embodiment 6 of this invention to the fuel injection valve support member. It is a schematic sectional drawing which shows the example which attached the partition which is Embodiment 7 of this invention to the fuel injection valve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Cylinder head, 2 Combustion space, 3 Fuel injection valve, 4 Injection hole, 5 Fuel jet, 8 Outer peripheral surface, 9, 22, 27 Partition, 10 Duct, 11, 26, 28 Upstream space, 12 Inlet part, 13 Inner circumference Surface, 15, 16, 20 flow path, 17 small nozzle, 21 air inlet, 23 support member.

Claims (10)

A duct having an inner peripheral surface that is provided in the vicinity of an injection port of a fuel injection valve facing a combustion space of an in-cylinder direct injection engine and surrounds an outer peripheral surface of a fuel jet injected from the injection port close to and away from the fuel injection valve; Air in the upstream space upstream of the duct of the jet is attracted into the duct by the flow of the fuel jet and mixed with the fuel jet, and the duct is interposed between the duct and the upstream space. circumference of only partially the fuel injection mechanism of the in-cylinder direct injection engine flow path which communicates with the upstream side space characterized that you have provided the duct.   The fuel injection mechanism for a direct injection engine according to claim 1, further comprising a partition wall that supports the duct and substantially partitions the upstream space from the combustion space.   The fuel injection mechanism for an in-cylinder direct injection engine according to claim 2, wherein the partition wall is fixed to a cylinder head of the engine.   The fuel injection mechanism for a direct injection engine according to claim 2, wherein the partition wall is fixed to a support member that supports the fuel injection valve to the cylinder head.   The fuel injection mechanism for a direct injection engine according to claim 2, wherein the partition wall is fixed to a fuel injection valve.   The said partition is equipped with the inlet in the position away from the said duct, The air in the said combustion space is replenished to the said upstream space, The any one of Claims 2-5 characterized by the above-mentioned. Fuel injection mechanism for in-cylinder direct injection engines.   The in-cylinder direct injection according to any one of claims 1 to 6, wherein the duct includes an inlet portion having a radius of curvature large enough to prevent separation of air. Engine fuel injection mechanism.   8. The duct according to claim 1, wherein the inner peripheral surface of the duct has a shape extending substantially along a part of the outer peripheral surface of the fuel jet pattern. The fuel injection mechanism of the in-cylinder direct injection engine described. 9. The fuel injection valve according to claim 1, wherein the fuel injection valve includes a plurality of small nozzle holes, and the flow path is in a position substantially facing the small nozzle holes . 10 . The fuel injection mechanism of the in-cylinder direct injection engine described. 9. The fuel injection valve according to claim 1, wherein the fuel injection valve includes a plurality of small nozzle holes, and the fluid is in a position substantially facing a space between the small nozzle holes . A fuel injection mechanism for an in-cylinder direct injection engine according to item 1 .

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