JP4036037B2 - Fuel injection nozzle for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection nozzle for an internal combustion engine suitable for a direct injection diesel engine, a direct injection gasoline engine, or the like.
[0002]
[Prior art]
In a fuel injection nozzle with multiple injection holes in which a plurality of injection holes are opened and closed by the tip of the needle valve, when the needle valve is eccentric from the center of the nozzle body during needle valve lift, the spray formed in each injection hole Becomes non-uniform, for example, leading to deterioration of the exhaust composition.
[0003]
In Japanese Patent Laid-Open No. 2000-257532, as a technique for suppressing the eccentricity of the needle valve during the lift, a plurality of fuel passages serving as fuel inlets are formed radially at the tip of the needle valve, and the upstream side A configuration is disclosed in which fuel guided through the needle valve is discharged from a plurality of fuel inlets at the tip. The fuel inlets are arranged uniformly in the circumferential direction of the needle valve, and the eccentricity of the needle valve is suppressed by the reaction force of the fuel discharged from each.
[0004]
[Problems to be solved by the invention]
The technique described in the above publication uses a pressure balance of fuel discharged from a plurality of fuel introduction ports located at equally spaced positions in the circumferential direction to generate a force for returning the needle valve to a concentric position, that is, a centering force. However, no consideration is given to the positional relationship between the fuel inlet and the nozzle hole.
[0005]
Actually, fuel flows from the annular gap between the needle valve and the nozzle body toward each nozzle hole. If the needle valve is eccentric to one side, the pressure of the fuel toward the nozzle hole also causes the needle valve to move to the opposite side. The ability to return, that is, the ability to align is obtained. And the aligning force by this nozzle hole becomes the largest when the nozzle hole position in the circumferential direction and the eccentric direction coincide. Therefore, when the needle valve is decentered toward one of the nozzle holes during the lift for some reason, the aligning force to push it back to the opposite side acts greatly, exceeding the concentric position and even more eccentric to the opposite side. I might let you. That is, there is a possibility that the amount of eccentricity is amplified more than the initial size. With respect to such a phenomenon, the above-described prior art cannot always provide a sufficient effect.
[0006]
Moreover, if the fuel introduction port is arranged at the same circumferential position as the nozzle hole, the alignment force for the initial eccentricity is generated in the same direction, and the amplification of the eccentricity is further deteriorated. Resulting in.
[0007]
[Means for Solving the Problems]
A fuel injection nozzle for an internal combustion engine according to the present invention includes a nozzle body and a needle valve disposed in the nozzle body so as to be liftable. The nozzle body has a plurality of nozzle holes formed at the tip thereof, and the inlet openings of the nozzle holes are located apart from each other in the circumferential direction. The needle valve is configured such that the tapered portion at the tip is seated on the seating surface of the nozzle body at a position upstream of the nozzle hole, and at least at the tip side portion of the needle valve, the inner circumference of the nozzle body An annular gap serving as a fuel flow path is formed between the two surfaces.
[0008]
In order to suppress the eccentricity of the needle valve, a plurality of fuel introduction ports that open from the needle valve or the nozzle body toward the annular gap are provided in the circumferential direction so as to introduce fuel into the annular gap from the upstream side. Is provided. At least a part of the injected fuel is supplied to the annular gap through this fuel inlet. The fuel inlet and the injection hole are provided at circumferential positions on opposite sides of the center line of the needle valve. Here, the “center line of the needle valve” means a center line in a state where the needle valve is not eccentric, and therefore there is no particular difference from the center line of the nozzle body.
[0009]
Alternatively , the circumferential position of each fuel inlet is not aligned with the circumferential position of each nozzle hole. That is, each of the plurality of fuel introduction ports is disposed at a position shifted in the circumferential direction with respect to the injection hole.
[0010]
FIG. 1 explains the principle of the alignment force generated by the fuel inlet, and shows a state in which the needle valve 102 is eccentric in one direction in the nozzle body 101. In this example, three fuel inlets 103 are provided radially on the needle valve 102 side, and pressurized fuel is discharged from each into the annular gap 104. Is eccentric, the fuel pressure at the outlet side of each fuel inlet 103 becomes non-uniform, and the reaction force f11 at the fuel inlet 103 closer to the nozzle body 101 becomes the reaction force f12, f13 at the other fuel inlet 103. Bigger than. Therefore, the resultant force f1 of the three acts as a centering force in a direction to return the needle valve 102 to the concentric position. This aligning force is similarly generated when the needle valve 102 is decentered in any direction, but as shown in the figure, when the needle valve 102 is decentered toward the direction in which one of the fuel introduction ports 103 is located. When the largest aligning force is generated and is decentered along the circumferential position where the fuel introduction port 103 does not exist, the generated aligning force is relatively small.
[0011]
On the other hand, FIG. 2 illustrates the alignment force due to the nozzle hole, and the magnitude of the alignment force f2 when the needle valve 102 is eccentric by a predetermined amount α as shown in FIG. Changes as shown in (a) depending on the positional relationship with the nozzle hole (particularly the inlet opening of the nozzle hole). That is, in the illustrated example, the five injection holes 105 are provided, but when the eccentricity is made in a direction coinciding with the circumferential position of the injection holes 105, a large aligning force f2 is generated and the two injection holes 105 are separated. When it is eccentric toward the center, the generated aligning force f2 is small. In addition, the alignment force f2 due to the nozzle hole varies depending on the lift amount of the needle valve 102, and when the lift amount is small (solid line) as shown in (a), it is larger than when the lift amount is large (broken line). A centering force f2 is generated.
[0012]
As described above, when the needle valve is initially decentered in the direction of one of the nozzle holes, a large alignment force f2 is generated by the nozzle hole, and conversely, the needle valve may be largely decentered in the opposite direction. In the present invention, since the fuel introduction port is located on the opposite side of any one of the injection holes that are in the initial eccentric direction, the movement of the needle valve to move to the opposite side beyond the concentric position is effectively regulated. The
[0013]
Further , if the circumferential position of each fuel inlet does not match the circumferential position of each nozzle hole, the eccentric direction in which the aligning force f2 is large and the eccentric direction in which the aligning force f1 is large do not match. Therefore, the initial eccentricity is not greatly amplified, and the eccentricity is effectively suppressed by the alignment force f1 by the fuel introduction port.
[0014]
【The invention's effect】
According to this invention, by making the circumferential position of the fuel inlet provided in the needle valve or nozzle body appropriate to the nozzle hole position, the needle valve that is initially eccentric in the direction of any nozzle hole can be obtained. It is possible to avoid the phenomenon of the next large eccentricity due to the aligning force, and it is possible to effectively suppress the eccentricity of the needle valve by the pressure balance of the plurality of fuel introduction ports. Therefore, it is possible to reduce the dispersion of the spray of each nozzle hole due to the eccentricity of the needle valve.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 3 is a cross-sectional view when the fuel injection nozzle 1 according to the present invention is applied to, for example, a direct injection diesel engine, and an intake port 5 and an upper surface of a cylinder block 3 in which a plurality of cylinders 2 are formed. A cylinder head 4 having an exhaust port 6 is fixed, and a piston 7 is slidably fitted in the cylinder 2. For example, a deep dish-shaped cavity 8 is recessed in the center of the top surface of the piston 7. On the cylinder head 4 side, a pair of intake valves 9 and exhaust valves 10 for opening and closing the ports 5 and 6 are provided for each cylinder, and a total of four intake valves 9 and exhaust valves 10 are provided. A fuel injection nozzle 1 is mounted at the center of the cylinder surrounded by the cylinder. The fuel injection nozzle 1 is mounted in a vertical posture facing the substantial center of the cavity 8 and along the cylinder center line.
[0017]
FIG. 4 is a cross-sectional view showing the main part of the fuel injection nozzle 1. A nozzle body 13 is fixed to the tip of a cylindrical nozzle holder 11 by a nozzle nut 12, and a needle valve 14 is slid at the center. It is held movable. More specifically, the large-diameter portion 14a on the base side of the needle valve 14 is slidably fitted to the cylindrical surface 13a on the inner periphery of the nozzle body 13, and the small-diameter portion 14b on the distal end side of the needle valve 14 and the above cylinder. An annular gap 18 serving as a fuel flow path is formed in a cylindrical shape between the surface 13a. The needle valve 14 receives the biasing force of the nozzle spring 16 via the push rod 15 and is always biased in the closing direction to close the nozzle hole 19. The needle valve 14 is lifted upward by the pressure of the fuel introduced into the annular gap 18 from the fuel inlet (not shown) through the fuel passage 17.
[0018]
5 to 7 show details of the tip portion of the fuel injection nozzle 1. A seating surface 21 made of a conical surface is formed at the tip of the nozzle body 13, and an injection hole 19 is formed in the seating surface 21. It is open. In this embodiment, five nozzle holes 19 are provided, and as shown in FIG. 6, each nozzle hole 19 extends along a radial line passing through the center of the nozzle body 13 so as to be radial when viewed from the axial direction. Is formed. In particular, in the illustrated example, the five nozzle holes 19 are formed at equal intervals in the circumferential direction, and accordingly, the inlet openings 19a in the seating surface 21 are also arranged at equal intervals in the circumferential direction, that is, every 72 °. Yes. Moreover, each nozzle hole 19 is formed so as to be directed obliquely downward at the same height position.
[0019]
On the other hand, the tapered portion 14 c at the tip of the needle valve 14 is composed of two conical surfaces 23 and 24 having slightly different angles, and the boundary between the two is in contact with the seating surface 21 as a seal line 22. That is, the two conical surfaces 23 and 24 positioned above and below the seal line 22 are not microscopically in close contact with the seating surface 21 and have a very slight wedge shape between the seating surface 21. There is a gap. The seal line 22 is seated on the seating surface 21 at a position upstream of the nozzle hole 19, and the inlet opening 19 a of the nozzle hole 19 is covered by the conical surface 24 on the tip side of the seal line 22. It has become.
[0020]
In addition, a fuel introduction port 31 is opened in the conical surface 23 on the base end side of the seal line 22. The number of the fuel introduction ports 31 is the same as the number of the nozzle holes 19, that is, five, and as shown in FIG. 7, along the radial line passing through the center of the needle valve 14 so as to be radial when viewed from the axial direction. Each is formed into a narrow channel. And it connects to the center part fuel passage 32 formed in the axial direction along the center of the needle valve 14, respectively. Further, as shown in FIG. 5, each fuel introduction port 31 is inclined obliquely downward so as to be substantially orthogonal to the opposing seating surface 21. If the fuel is discharged from the direction orthogonal to the seating surface 21, the dynamic pressure accompanying the fuel discharge is most effective.
[0021]
Here, the five fuel introduction ports 31 are formed at equal intervals in the circumferential direction, that is, every 72 °, and each nozzle hole 19 (strictly speaking, sandwiching the center line m of the needle valve 14). Each fuel inlet 31 is located at a circumferential position opposite to the inlet opening 19a). In other words, one fuel introduction port 31 is located at a circumferential position that is 180 ° away from any nozzle hole 19. The central fuel passage 32 is connected to a radial fuel passage 33 formed along the diametrical direction in the large diameter portion 14 a of the needle valve 14, and is described above via the fuel passage 34 provided in the nozzle body 13. The nozzle holder 11 always communicates with the fuel passage 17 of the nozzle holder 11. The fuel inlet 31, the central fuel passage 32, and the radial fuel passage 33 are, for example, secondarily machined into the needle valve 14. If necessary, the end portion can be plugged after drilling. It can be set as the structure which obstruct | occludes.
[0022]
Further, in this embodiment, since it is necessary to prevent the needle valve 14 from rotating with respect to the nozzle body 13, as shown in FIG. 9, the shaft portion 14d at the base end of the needle valve 14 has a rectangular cross section as a rotation restricting portion. The guide hole 37 of the stopper plate 36 is formed in a rectangular hole corresponding thereto. Therefore, the needle valve 14 is lifted without rotating in the circumferential direction, and the above-described positional relationship between the nozzle hole 19 and the fuel introduction port 31 is always maintained. The rotation restricting portion is not limited to the shaft portion 14d and the guide hole 37, and can be provided at an appropriate position of the needle valve 14.
[0023]
In the configuration of the above-described embodiment, fuel sent from a fuel injection pump (not shown) flows from the fuel passage 17 of the nozzle holder 11 to the fuel passage 34 of the nozzle body 13, the radial fuel passage 33 inside the needle valve 14, and the central portion. It is introduced into the annular gap 18 from the fuel inlet 31 at the tip of the needle valve 14 through the fuel passage 32. As described above, the needle valve 14 is lifted by this fuel pressure, each nozzle hole 19 is opened, and fuel injection is started. Here, since the five fuel introduction ports 31 are located at equal intervals in the circumferential direction of the needle valve 14 and high pressure fuel is discharged from each, the eccentricity of the needle valve 14 is regulated by the pressure balance.
[0024]
On the other hand, when the needle valve 14 is eccentric to one side for some reason, particularly when it is eccentric so as to approach any one of the nozzle holes 19 at a stage where the lift amount is small, as described above, the alignment force by the nozzle holes 19 is reduced. It is strongly generated and tries to push the needle valve 14 back to the opposite side excessively. At this time, the fuel introduction port 31 is located on the opposite side separated by 180 °, so that the movement of the fuel discharged from the fuel introduction port 31 is changed. The pressure limits excessive movement of the needle valve 14. Therefore, the eccentricity is not amplified by the aligning force, and the concentric state is quickly converged.
[0025]
Next, FIGS. 10 to 13 show an embodiment in which a fuel introduction port 41 is provided on the nozzle body 13 side. The other basic configuration is the same as that of the above-described embodiment, and the configuration of the nozzle hole 19 is not particularly different from the above-described embodiment as shown in FIGS. In this embodiment, the seating surface 21 of the nozzle body 13 is provided with the same number of fuel inlets 41 as the number of nozzle holes 19, that is, five fuel introduction ports 41. As shown in FIG. 13, these fuel introduction ports 41 are each formed in a narrow passage shape along a radial line passing through the center of the nozzle body 13 so as to form a radial shape when viewed from the axial direction. The ends of five axial fuel passages 42 respectively formed along the axial direction inside are connected to each other. Further, as shown in FIG. 11, each fuel introduction port 41 is provided toward the conical surface 23 on the base end side with respect to the seal line 22, and is substantially orthogonal to the opposing conical surface 23. That is, it is provided in a direction in which the illustrated angle φ is approximately 90 °. In this way, the dynamic pressure works most effectively. FIG. 14 shows the relationship between the angle φ and the alignment force f <b> 1 by the fuel introduction port 41.
[0026]
The five fuel introduction ports 41 are formed at equal intervals in the circumferential direction, that is, every 72 °, in the same manner as in the above-described embodiment, and in particular, with the center line of the needle valve 14 interposed therebetween, The fuel inlet 41 is located at the opposite circumferential position. In other words, the five injection holes 19 and the five fuel introduction ports 41 are alternately arranged at an interval of 36 °. The axial fuel passage 42 is always in communication with the fuel passage 17 of the nozzle holder 11 described above via a fuel passage 34 provided in the nozzle body 13. The fuel inlet 41 and the axial fuel passage 42 are, for example, secondarily machined in the nozzle body 13 and are easily formed by closing the end with a plug after drilling from the outside. be able to.
[0027]
Also in this embodiment, the eccentricity of the needle valve 14 is regulated by the fuel introduction port 41 as in the above-described embodiment. In particular, in this embodiment, since the fuel introduction port 41 is provided on the nozzle body 13 side, the circumferential positional relationship between the injection hole 19 and the fuel introduction port 41 is fixedly determined. Such a mechanism for regulating the rotation of the needle valve 14 becomes unnecessary.
[0028]
In the above embodiment, the fuel introduction port 41 has a linear passage shape with a constant cross section. However, as shown in FIG. 15, the fuel introduction port 41 is expanded in the circumferential direction toward the inner peripheral side of the nozzle body 13. The mouth 41 may be configured. In the illustrated example, each fuel inlet 41 is formed in a shape that expands in a parabolic shape when viewed from the axial direction. In such a shape of the fuel inlet 41, the dynamic pressure is highest in the central portion where the axial fuel passage 42 is located, and the dynamic pressure gradually decreases as the distance from the circumferential direction increases. That is, the pressure distribution has a shape close to a sine waveform. Since this corresponds to the distribution of the aligning force by the nozzle hole 19 shown in FIG. 2A, the characteristic is suitable for canceling the excessive aligning force from the opposite side.
[0029]
As described above, as shown in FIG. 2A, the aligning force by the nozzle hole 19 is large at the time of low lift, but is small at the time of high lift. Therefore, the application of dynamic pressure by the fuel inlet 41 is not performed. It becomes unnecessary. In addition, at the time of high lift where the alignment force by the nozzle hole 19 is small, the eccentricity is less likely to occur if the dynamic pressure by the fuel introduction port 41 is reduced. Therefore, it is preferable to control the flow rate of the fuel supplied from the fuel introduction port 41 so that the flow rate decreases at the time of high lift according to the lift amount of the needle valve 14 as shown in FIG.
[0030]
FIG. 17 shows an embodiment of the fuel injection nozzle 1 that realizes the flow rate characteristic as shown in FIG. 16 without requiring external control. This is provided with a flow rate adjusting mechanism using the needle valve 14 itself as a valve body, the tip of the fuel passage 34 opens as a first port 51 in the cylindrical surface 13a of the inner periphery of the nozzle body 13, and “first” The base end of the axial fuel passage 42 corresponding to the “no fuel passage” is also opened as a second port 52 in the cylindrical surface 13a. The second port 52 is located below the first port 51, that is, on the distal end side of the nozzle body 13, and actually includes a total of five second ports 52 corresponding to the fuel introduction ports 41. ing. Further, a bypass passage 53 corresponding to a “second fuel passage” whose tip always communicates with the annular gap 18 is formed inside the nozzle body 13, and its base end opens to the cylindrical surface 13 a as a third port 54. ing. The third port 54 opens at an intermediate height between the first port 51 and the second port 52.
[0031]
On the other hand, the large-diameter portion 14a of the needle valve 14 is provided with a first communication port 61 and a second communication port 62 located on the tip side from this. These first and second communication ports 61 and 62 communicate with each other inside the needle valve 14.
[0032]
FIG. 17A shows a state in which the needle valve 14 is slightly lifted, and the first communication port 61 communicates with the first port 51 during such low lift and when the needle valve 14 is seated. The second communication port 62 communicates with the second port 52. The third port 54 is closed between the first communication port 61 and the second communication port 62. Therefore, the entire amount of fuel sent from the fuel passage 34 flows to the annular gap 18 through the fuel introduction port 41. On the other hand, when the needle valve 14 is lifted by a predetermined amount, the second port 52 is closed and the third port 54 and the second communication port 62 communicate with each other as shown in FIG. In this state, fuel does not flow from the fuel introduction port 41, and fuel is supplied to the annular gap 18 via the bypass passage 53. In the middle of the transition to the state (b), the second port 52 is gradually closed and at the same time the third port 54 is gradually opened, so that the flow rate ratio of both changes continuously.
[0033]
As mentioned above, although one Example of this invention was described, this invention is not limited to the above-mentioned Example. For example, in the above embodiment, the example in which the needle valve is lifted by the fuel pressure has been described. However, the present invention can be similarly applied to a fuel injection nozzle that lifts the needle valve by a solenoid or the like. Further, the present invention can be applied not only to a diesel engine but also to a fuel injection nozzle for a direct injection gasoline engine.
[0034]
In the above embodiment, the five nozzle holes are formed at equal intervals and in exactly the same shape. However, the present invention can also be applied to the case where the nozzle holes are not arranged at equal intervals. A configuration in which the inclination and height position of the hole are different is also possible.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of alignment force by a fuel inlet.
FIG. 2 is an explanatory diagram of alignment force by an injection hole. FIG. 3 is a cross-sectional view of a direct injection diesel engine in which a fuel injection nozzle according to the present invention is used.
FIG. 4 is a cross-sectional view showing a main part of a fuel injection nozzle according to the present invention.
FIG. 5 is an enlarged view of only the tip portion.
6 is a cross-sectional view taken along line AA in FIG.
7 is a cross-sectional view taken along line BB in FIG.
FIG. 8 is a cross-sectional view showing a passage structure inside a needle valve.
9 is a cross-sectional view taken along line CC in FIG.
FIG. 10 is a cross-sectional view of a main part of a fuel injection nozzle showing a different embodiment.
FIG. 11 is an enlarged view of only the tip portion.
12 is a cross-sectional view taken along line DD of FIG.
13 is a cross-sectional view taken along the line EE of FIG.
FIG. 14 is a characteristic diagram showing the relationship between the angle φ of the fuel inlet with respect to the conical surface and the alignment force f1.
15 is a cross-sectional view similar to FIG. 13, showing another embodiment in which the shape of the fuel inlet is changed.
FIG. 16 is a characteristic diagram showing the relationship between the lift amount and the flow rate of the fuel inlet.
FIGS. 17A and 17B are cross-sectional views showing an embodiment provided with a flow rate adjusting mechanism, in which FIG. 17A shows a state during low lift and FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel injection nozzle 13 ... Nozzle body 14 ... Needle valve 18 ... Annular gap 19 ... Injection hole 31 ... Fuel introduction port 41 ... Fuel introduction port

Claims (7)

A nozzle body in which a plurality of nozzle holes are formed at the tip, and the inlet openings of the nozzle holes are spaced apart from each other in the circumferential direction;
The nozzle body is arranged so as to be liftable, and forms an annular gap serving as a fuel flow path with the nozzle body inner peripheral surface at least at the tip side portion, and the tapered portion at the tip is upstream of the nozzle hole. A needle valve seated on the seating surface of the nozzle body at the position of
In a fuel injection nozzle of an internal combustion engine comprising:
A plurality of fuel inlets that open from the needle valve or nozzle body toward the annular gap are arranged in the circumferential direction so as to introduce at least part of the fuel into the annular gap from the upstream side,
A fuel injection nozzle for an internal combustion engine, wherein the fuel introduction port and the injection hole are provided at circumferential positions on opposite sides of the center line of the needle valve.   The plurality of nozzle holes are arranged at equal intervals in the circumferential direction, and the same number of fuel introduction ports as the nozzle holes are arranged at circumferential positions 180 degrees away from each nozzle hole. A fuel injection nozzle for an internal combustion engine according to claim 1.   3. The fuel injection nozzle for an internal combustion engine according to claim 1, wherein the fuel introduction port is provided in the needle valve, and further includes a rotation restricting portion for restricting the rotation of the needle valve with respect to the nozzle body. .   The plurality of fuel introduction ports are formed in the nozzle body so as to form a radial shape when viewed from the axial direction, and are respectively connected to fuel passages extending in the axial direction inside the nozzle body. 3. A fuel injection nozzle for an internal combustion engine according to 1 or 2.   5. The fuel introduction port according to claim 4, wherein the fuel introduction port is disposed at a position facing the taper portion at the tip of the needle valve, and is formed along a direction substantially orthogonal to the conical surface of the taper portion. The fuel injection nozzle of the internal combustion engine described.   6. The fuel injection nozzle for an internal combustion engine according to claim 4, wherein the fuel introduction port has a shape that expands in a circumferential direction toward the inner peripheral side of the nozzle body.   A first fuel passage leading to the fuel introduction port and a second fuel passage leading to the annular gap are provided in the nozzle body, and the respective flow rate ratios depend on the lift amount of the needle valve. 5. A flow rate adjusting mechanism using the needle valve as a valve body so as to change, wherein the flow rate ratio of the first fuel passage is increased during low lift. A fuel injection nozzle for an internal combustion engine according to any one of claims 6 to 10.

Images