JP2002317735A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in arranging a secondary sliding shaft part on a valve part 14 side of a needle 3 for preventing the eccentricity of a valve seat 7 and the valve part 14, wherein the increase of the sliding resistance is caused even when the eccentricity is not generated, and the strong sliding of the secondary sliding shaft part is caused when the eccentricity is generated, to result in defective sliding. SOLUTION: The valve part 14 is composed of an upper truncated conical part 16 and a lower conical tip part 17, an expanding angle of the truncated conical part 16 is smaller than an expanding angle of the valve seat 7, and the difference therebetween is 4 deg. or less. When the valve part 14 is separated from the valve seat 7, and the eccentricity is generated, the unbalance in pressure is generated in a fuel passage formed by a clearance between the truncated conical part 16 and the valve seat 7. The fuel hardly flows at an eccentric side, and the fuel easily flows at an anti-eccentric side, whereby the pressure in the fuel passage at the eccentric side is relatively increased, and the aligning force for the valve part 14 is generated to automatically align the valve part 14 to a shaft center of the valve seat 7. As a result, the eccentricity can be prevented without increasing the sliding resistance and the defective sliding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle for injecting high-pressure fuel into an internal combustion engine, and more particularly to a technique for centering a needle that reciprocates in an axial direction in a nozzle body.

[0002]

2. Description of the Related Art When an eccentricity occurs between a valve portion of a needle and a valve seat of a nozzle body, an imbalance occurs in an annular fuel passage (an annular gap between the needle and the nozzle body). Then, when there are a plurality of injection holes on the downstream side, the injection amount of each injection hole is biased, and the spray shape differs between the injection holes. This problem particularly occurs in a VCO nozzle having a plurality of injection holes formed in a valve seat of a nozzle body.

The eccentricity between the valve portion of the needle and the valve seat of the nozzle body is mainly caused by the following factors. It is caused by machining tolerance between the needle and the nozzle body. That is, eccentricity occurs due to the tolerance of coaxiality between the sliding shaft portion of the needle and the valve portion and the tolerance of coaxiality between the sliding hole of the nozzle body and the valve seat. Due to the clearance between the sliding shaft of the needle and the sliding hole of the nozzle body, the needle is tilted and eccentricity occurs. If the distance from the sliding portion (the portion where the sliding shaft portion and the sliding hole slide) to the valve portion is long, the eccentricity of the eccentricity is amplified and the eccentricity is increased. In addition, the eccentricity is caused by the expansion of the diameter of the sliding hole due to the assembling torque (tightening of the retaining nut, attachment to the internal combustion engine), thermal expansion due to the heat of the internal combustion engine, and expansion of the diameter of the sliding hole due to thermal deformation. In some cases, the clearance increases and the degree of eccentricity increases.

[0004] The force for inclining the needle with respect to the nozzle body is generated by the following factors. Eccentricity of the urging force for urging the needle in the valve closing direction (tolerance of flatness between the pressure pin and the contact surface of the needle valve, runout, etc.) generates a force for inclining the needle. When applied to a pressure accumulating fuel injection device, a high pressure is constantly applied to a fuel reservoir in a nozzle body. In a state where the needle is inclined by the clearance of the sliding portion, a circumferential imbalance also occurs in the clearance, and high pressure fuel is applied to the unbalanced portion, and the pressure generates a side load on the needle. Tilt the needle.

[0005] As a technique for suppressing the inclination of the needle, for example, Japanese Patent Application Laid-Open Nos. Hei 4-252861 and Hei 4-3116
As disclosed in Japanese Patent Application Laid-Open No. 74-342869 and Japanese Patent Application Laid-Open No. 4-342869, there is known a technique in which a second sliding shaft is provided also on the valve side of a needle.

[0006]

As disclosed in the above publication, if the second sliding shaft is provided on the valve side of the needle, even if the valve and the valve seat are not eccentric. The sliding resistance increases. When eccentricity occurs between the valve portion and the valve seat, the second sliding shaft portion strongly slides in order to suppress the eccentricity, thereby causing poor sliding of the needle,
This causes a failure of the fuel injection nozzle.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to increase the sliding resistance of a needle and to prevent poor sliding of the needle by adjusting the valve portion of the needle to the valve of the valve body. Another object of the present invention is to provide a fuel injection nozzle capable of self-centering on a seat.

[0008]

[Means for Solving the Problems] [Claim 1] A hydraulic alignment section provided in a fuel injection nozzle is operated by a pressure of high-pressure fuel supplied between a nozzle body and a needle.
The valve part is automatically aligned with the axis of the valve seat. That is, even when the valve portion and the valve seat are misaligned due to the processing tolerance of the needle and the nozzle body, the valve portion is moved to the axial center of the valve seat by the pressure of the high-pressure fuel supplied between the guide hole and the needle. Is automatically aligned. Further, even in a state in which the needle is liable to be inclined due to the clearance between the sliding shaft portion of the needle and the guide hole, the valve portion is moved by the pressure of the high-pressure fuel supplied between the guide hole and the needle. Is automatically aligned with the axis of

As described above, the occurrence of eccentricity between the valve portion of the needle and the valve seat of the nozzle body can be prevented without increasing the sliding resistance of the needle and causing poor sliding. Unevenness in the injection amount does not occur, and variations in the injection amount and in the fuel spray shape in each injection hole can be suppressed.

[Means of Claim 2] The hydraulic alignment portion may be formed in a needle. That is, the hydraulic alignment portion may be provided by changing the shape of the needle.

According to a third aspect of the present invention, the hydraulic alignment portion provided on the needle side may be provided as a truncated conical portion forming an annular minute clearance with the nozzle body.

According to a fourth aspect of the present invention, the truncated cone portion is provided above the valve portion, and the valve portion may be provided so as to form an annular minute gap between the valve portion and the valve seat. good.

[0013] According to a fifth aspect of the present invention, a hydraulic centering portion is constituted by a body-side truncated cone portion formed above the valve seat and a needle-side truncated cone portion formed above the valve portion. May be provided so as to form an annular minute gap between the body-side frustoconical portion and the needle-side frustoconical portion even when seated on the valve seat.

According to a sixth aspect of the present invention, a hydraulic centering portion is provided by increasing the diameter of the shaft as it approaches the valve portion.
An annular minute gap may be formed between the valve portion and the guide hole.

[Means of Claim 7] The shaft may be provided so as to be elastically deformable in the axial direction. With this arrangement, even when the sliding shaft of the needle is tilted due to the clearance between the sliding shaft of the needle and the guide hole, the shaft is subjected to the radial force received by the hydraulic alignment unit, so that the shaft is tilted. The valve portion is elastically deformed, and the valve portion is automatically aligned with the axis of the valve seat.

[Embodiment 8] The sliding distance in the axial direction between the guide hole and the sliding shaft portion of the needle may be provided short. With this provision, when applied to a pressure accumulating fuel injection device, the lateral load generated in the clearance of the sliding portion is reduced, and the force for inclining the needle is reduced.
Therefore, the force for automatically aligning the valve portion with the axis of the valve seat is relatively increased, and the eccentricity between the valve portion and the valve seat can be further reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described using a plurality of examples. [First Embodiment] FIGS. 1 to 3 show a first embodiment.
FIG. 1 is a sectional view of the fuel injection nozzle 1. The fuel injection nozzle 1 according to the present embodiment injects high-pressure fuel into a cylinder of a diesel engine. As shown in FIG. 1, the fuel injection nozzle 1 includes a nozzle body 2 and a needle 3 and is mounted on a nozzle holder (not shown). Attached to the engine.

The nozzle body 2 has a guide hole 4 into which the needle 3 is inserted, a fuel reservoir 5 provided in the middle of the guide hole 4, a fuel introduction passage 6 leading to the fuel reservoir 5, and high-pressure fuel injection. And a plurality of injection holes 8 are formed. The guide hole 4 is formed with a constant inner diameter from the upper end surface of the nozzle body 2 to the lower end portion of the nozzle body 2, and an opening peripheral portion opening on the upper end surface of the nozzle body 2 is chamfered. The lower end of the guide hole 4 has a conical valve seat 7.
A plurality of injection holes 8 are formed on the downstream side of the valve seat 7.

The fuel reservoir 5 is formed by enlarging the inner diameter of the guide hole 4 over the entire circumference, and forms an annular space on the outer periphery of the needle 3 inserted into the guide hole 4. Hereinafter, the guide hole 4 above the fuel reservoir 5 is referred to as a sliding hole 9. The fuel introduction passage 6 is a passage for guiding the high-pressure fuel supplied to the nozzle holder to the fuel reservoir 5, and is formed from the upper end surface of the nozzle body 2 to the fuel reservoir 5. The injection hole 8 has an inlet opening at the upper surface on the downstream side of the valve seat 7 and is provided through a conical wall 10 forming the lower end of the nozzle body 2.
Is open on the outer peripheral surface of the. The plurality of injection holes 8 are formed so as to inject fuel evenly with respect to the axis.

The needle 3 is provided with a sliding hole 9 of the nozzle body 2.
A sliding shaft portion 11 inserted with a clearance of several μm through
A pressure receiving surface 12 formed below the sliding shaft portion 11, and a small diameter shaft-shaped shaft 13 extending below the pressure receiving surface 12.
And a conical valve portion 14 that sits on and separates from a valve seat 7 formed at the lower end of the guide hole 4 to open and close the injection hole 8. The sliding shaft portion 11 is connected to the fuel reservoir 5 and the low pressure side. Are provided so as to be able to reciprocate in the axial direction inside the guide hole 4 while sealing between them.

The pressure receiving surface 12 is provided to have a tapered diameter from the lower end of the sliding shaft portion 11 and is arranged facing the fuel reservoir 5. The outer diameter of the shaft 13 is smaller than that of the sliding shaft 11,
The guide hole 4 is inserted below the fuel reservoir 5 and
And a fuel passage 15 is formed between them.

As shown in FIG. 2, the valve portion 14 at the tip of the needle 3 has an upper frustoconical portion 16 and a lower conical tip portion 1.
7, and a sheet line 18 is formed at the boundary. The spread angle of the truncated conical portion 16 is smaller than the spread angle of the valve seat 7, but the difference is set to 4 ° or less. Similarly, the divergence angle of the conical tip 17 is larger than the divergence angle of the valve seat 7, and the difference is 2 °.
It is provided below. That is, when the valve portion 14 is seated on the valve seat 7, the seat wire 18 of the valve portion 14 abuts on the valve seat 7 to cut off the communication between the fuel passage 15 and the injection hole 8. When the valve separates from the valve seat 7, the seat line 18 of the valve portion 14 separates from the valve seat 7, and the fuel passage 15 and the injection hole 8
And high-pressure fuel is injected from the injection hole 8. A large-diameter shaft 19 having a larger diameter than the small-diameter shaft 13 is provided at the large-diameter end of the truncated cone 16.

The truncated conical portion 16 corresponds to a hydraulic alignment portion, forms an annular minute gap with the surrounding valve seat 7, and is supplied between the guide hole 4 and the needle 3. The valve part 14 is automatically centered on the axis of the valve seat 7 by the pressure of the high-pressure fuel. This automatic alignment will be described with reference to FIG. When the valve portion 14 is separated from the valve seat 7 and the valve portion 14 is eccentric with respect to the valve seat 7, the pressure in the fuel passage formed by the gap between the frustoconical portion 16 and the valve seat 7 is increased. Imbalance occurs. In the fuel path on the eccentric side, the fuel is difficult to flow, and the fuel is easy to flow on the anti-eccentric side. Therefore, the pressure in the fuel path on the eccentric side relatively increases, and a force for aligning the valve portion 14 is generated. The valve section 14 is automatically aligned with the axis of the valve seat 7. The shaft 13 is made as small as possible while ensuring safety so that the valve portion 14 is easily aligned by the force generated in the valve portion 14.
The shaft 13 is provided so as to be elastically deformed.

Next, the operation of the fuel injection nozzle 1 will be described. High-pressure fuel pumped from a fuel pump (not shown) is stored in the fuel reservoir 5 via the fuel introduction path 6, and when the fuel pressure of the fuel reservoir 5 (the force applied to the pressure receiving surface 12) becomes higher than the valve closing pressure of the needle 3. Then, the needle 3 is pushed up to lift the inside of the guide hole 4 by a predetermined lift amount. Then
The seat line 18 of the valve section 14 is separated from the valve seat 7, the fuel passage 15 and the injection hole 8 communicate with each other, and high-pressure fuel is injected from the plurality of injection holes 8 into the cylinder of the engine. Then, the pressure receiving surface 12
When the fuel pressure applied to the needle 3 becomes smaller than the valve closing pressure of the needle 3, the needle 3 descends in the guide hole 4 and
8 comes into contact with the valve seat 7, the communication between the fuel passage 15 and the injection hole 8 is cut off, and the fuel injection from the injection hole 8 is stopped.

(Effects of the Embodiment) The fuel injection nozzle 1 of the present embodiment is fastened and fixed to the nozzle holder by a retaining nut (not shown) or the like. In comparison, both ends of the sliding hole 9 are particularly enlarged in diameter. In addition, the diameter of the sliding hole 9 also increases due to expansion or deformation due to heat of the engine. As a result, the clearance between the sliding shaft portion 11 of the needle 3 and the sliding hole 9 of the nozzle body 2 becomes large, the needle 3 tends to be inclined, and the valve portion 14 and the valve seat 7 tend to be eccentric. Become. Further, the sliding shaft portion 11 of the needle 3 and the valve portion 14
Of the concentricity of the nozzle body 2, the sliding hole 9 of the nozzle body 2 and the valve seat 7
The eccentricity may occur between the valve section 14 and the valve seat 7 depending on the tolerance of the coaxiality.

On the other hand, in this embodiment, the frustoconical portion 16 (hydraulic alignment portion) provided integrally with the valve portion 14 is controlled by the pressure of the high-pressure fuel supplied between the nozzle body 2 and the needle 3. , The valve portion 14 is automatically aligned with the axis of the valve seat 7. That is, even when the valve portion 14 and the valve seat 7 are displaced due to the processing tolerance between the needle 3 and the nozzle body 2, the radial action due to the pressure of the high-pressure fuel supplied between the guide hole 4 and the needle 3. By the force, the valve portion 14 is automatically aligned with the axis of the valve seat 7. In addition, even if the needle 3 is easily inclined due to the clearance between the sliding shaft portion 11 of the needle 3 and the guide hole 4, the pressure of the high-pressure fuel supplied between the guide hole 4 and the needle 3 causes the needle 3 to tilt. The valve section 14 is automatically aligned with the axis of the valve seat 7. Thus, the needle 3
The eccentricity of the valve portion 14 of the needle 3 and the valve seat 7 of the nozzle body 2 can be prevented without increasing the sliding resistance and poor sliding, and the injection amount of each injection hole 8 is uneven. Does not occur, and it is possible to suppress a variation in the injection amount and a variation in the fuel spray shape in each injection hole 8.

[Second Embodiment] FIG. 4 shows a second embodiment, and is a sectional view of a main part of a fuel injection nozzle 1. As shown in FIG. The fuel injection nozzle 1 of the second embodiment has a body-side truncated cone portion 21 formed above the valve seat 7 and a needle-side truncated cone portion 22 formed above the valve portion 14. The spread angle of the base portion 22 is smaller than the spread angle of the body-side truncated cone portion 21, but the difference is 2
° or less. In other words, even when the valve portion 14 is seated on the valve seat 7, an annular minute gap is provided between the body-side truncated cone portion 21 and the needle-side truncated cone portion 22. I have.

With this arrangement, the valve portion 14 is automatically centered on the axis of the valve seat 7 by the pressure of the high-pressure fuel supplied between the body-side truncated cone portion 21 and the needle-side truncated cone portion 22. Can be done. That is, when the valve portion 14 is separated from the valve seat 7 and the valve portion 14 is eccentric with respect to the valve seat 7, the gap between the body-side truncated cone portion 21 and the needle-side truncated cone portion 22 causes a gap. A pressure imbalance occurs in the formed fuel passage. In the fuel path on the eccentric side, the fuel is difficult to flow, and the fuel is easy to flow on the anti-eccentric side. Therefore, the pressure in the fuel path on the eccentric side relatively increases, and a force for aligning the valve portion 14 is generated. The valve section 14 is automatically aligned with the axis of the valve seat 7. In addition,
In the second embodiment, an example in which the second embodiment is combined with the first embodiment is shown, but only the second embodiment may be adopted. When combined with the first embodiment, the angle of the gap formed between the nozzle body 2 and the truncated cone 16 and the angle of the gap formed between the nozzle body 2 and the needle-side truncated cone 22 are , May be the same or different.

[Third Embodiment] FIG. 5 shows a third embodiment, and is a sectional view of the fuel injection nozzle 1. As shown in FIG. This third
In the fuel injection nozzle 1 of the embodiment, the diameter of the shaft 13 is increased toward the lower side to form a hydraulic alignment portion on the lower side of the shaft 13. An annular minute gap is formed between the lower large-diameter portion 31 and the guide hole 4. The shaft 13
The diameter of the lower end portion 31a (the maximum diameter of the large diameter portion 31) is set so that the annular fuel passage formed between the nozzle body 2 and the nozzle body 2 does not cause a decrease in fuel pressure.

By providing such a shaft, the shaft 1
The valve portion 14 can be automatically centered on the axis of the valve seat 7 by the pressure of the high-pressure fuel supplied between the lower large-diameter portion 31 and the lower side of the guide hole 4. That is, when the valve portion 14 is separated from the valve seat 7 and the valve portion 14 is eccentric with respect to the valve seat 7, the large diameter portion 31 on the lower side of the shaft 13 and the lower side of the guide hole 4 Pressure imbalance occurs in the fuel passage formed by the gap. In the fuel path on the eccentric side, the fuel is difficult to flow, and the fuel is easy to flow on the anti-eccentric side. Therefore, the pressure in the fuel path on the eccentric side relatively increases, and a force for aligning the valve portion 14 is generated. The valve section 14 is automatically aligned with the axis of the valve seat 7. In the third embodiment, an example in which the third embodiment is combined with the first embodiment is shown, but only the third embodiment may be adopted. Further, it may be combined with the second embodiment. Further, it may be combined with the first and second embodiments.

Fourth Embodiment FIG. 6 shows a fourth embodiment, and is a sectional view of the fuel injection nozzle 1. As shown in FIG. The first
In the third to third embodiments, the clearance between the sliding hole 9 and the sliding shaft portion 11 is allowed, and the needle 3 is inclined by the clearance to align the valve portion 14 with the axis of the valve seat 7. Was assumed. However, the fuel injection nozzle 1 of the fourth embodiment is provided with a short sliding distance in the axial direction between the guide hole 4 and the sliding shaft portion 11 so that the lateral clearance generated by the high-pressure fuel is provided in the clearance of the sliding portion. Reduce the load,
This is to reduce the force for inclining the needle 3. With such provision, the force for automatically aligning the valve portion 14 with the axis of the valve seat 7 is relatively increased, and the eccentricity between the valve portion 14 and the valve seat 7 can be further reduced. Specifically, in the fourth embodiment, a large-diameter hole 41 is formed above the guide hole 4 and the sliding hole 9 is formed.
Is reduced in axial length.

[Fifth Embodiment] FIG. 7 shows a fifth embodiment and is a sectional view of the fuel injection nozzle 1. As shown in FIG. This fifth
In the embodiment, the axial dimension of both the sliding hole 9 and the sliding shaft portion 11 is shortened, and the same effect as in the fourth embodiment is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection nozzle (first embodiment).

FIG. 2 is a sectional view of a main part of a fuel injection nozzle (first embodiment).

FIG. 3 is a sectional view of a main part of a fuel injection nozzle showing an eccentric state (first embodiment).

FIG. 4 is a sectional view of a main part of a fuel injection nozzle (second embodiment).

FIG. 5 is a sectional view of a fuel injection nozzle (third embodiment).

FIG. 6 is a sectional view of a fuel injection nozzle (fourth embodiment).

FIG. 7 is a sectional view of a fuel injection nozzle (fifth embodiment).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle 2 Nozzle body 3 Needle 4 Guide hole 7 Valve seat 8 Injection hole 9 Sliding hole 11 Sliding shaft part 13 Shaft 14 Valve part 16 Conical part (Hydraulic alignment part of the first embodiment) 21 Body side Frustoconical part (hydraulic alignment part of the second embodiment) 22 Needle-side truncated cone part (hydraulic alignment part of the second embodiment) 31 Large diameter part (hydraulic alignment part of the third embodiment)

Claims (8)

[Claims] 1. A nozzle body having a guide hole formed from an upper end surface to a lower end portion, a valve seat formed at a lower end portion of the guide hole, and a plurality of injection holes opened downstream of the valve seat. A sliding shaft portion slidably inserted into the guide hole on the side opposite to the injection hole, a valve portion that sits on and separates from the valve seat to open and close the injection hole, and connects the sliding shaft portion to the valve portion. A needle having a shaft, when the valve portion is separated from the valve seat and the injection hole is opened,
A fuel injection nozzle for injecting high-pressure fuel supplied between the guide hole and the needle from the injection hole, the fuel injection nozzle comprising a high-pressure fuel supplied between the nozzle body and the needle; A fuel injection nozzle, comprising: a hydraulic alignment portion for automatically aligning the valve portion with the axis of the valve seat by fuel pressure. 2. The fuel injection nozzle according to claim 1, wherein the hydraulic alignment portion is formed on the needle. 3. The fuel injection nozzle according to claim 1, wherein the hydraulic alignment portion is a truncated cone that forms an annular minute gap with the nozzle body. Fuel injection nozzle. 4. The fuel injection nozzle according to claim 3, wherein the truncated cone portion is provided above the valve portion, and is annular between the valve portion and the valve seat even when the valve portion is seated on the valve seat. A fuel injection nozzle characterized by forming a minute gap. 5. The fuel injection nozzle according to claim 1, wherein the hydraulic alignment portion includes a body-side truncated cone formed above the valve seat and a needle-side truncated cone formed above the valve portion. A fuel injection nozzle, wherein an annular minute gap is formed between the body-side truncated cone portion and the needle-side truncated cone portion even when the valve portion is seated on the valve seat. . 6. The fuel injection nozzle according to claim 2, wherein the hydraulic alignment portion is provided by increasing the diameter of the shaft as it approaches the valve portion, and between the shaft and the guide hole on the valve portion side. A fuel injection nozzle characterized in that an annular minute gap is formed in the fuel injection nozzle. 7. The fuel injection nozzle according to claim 1, wherein the shaft is provided so as to be elastically deformable in an axial direction. 8. The fuel injection nozzle according to claim 1, wherein an axial sliding distance between the guide hole and the sliding shaft portion is short. nozzle.